Smithy Midas 1220 XL Operator's Manual

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MIDAS 1220 XL

COMBINATION LATHE/MILL/DRILL

OPERATOR’S MANUAL

Updated August, 2008

170 Aprill Dr., Ann Arbor, MI, USA 48103

Toll Free 1-800-476-4849

www.smithy.com

170 Aprill Dr., Ann Arbor, Michigan, USA 48103 Toll Free Hotline: 1-800-476-4849

Fax: 1-800-431-8892 International: 734-913-6700 International Fax: 734-913-6663

All images shown are from Midas 1220 XL machine.

All rights reserved. No part of this manual may be reproduced or transmitted in any form by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of Smithy Co. For information on getting permission for reprints and excerpts, comments, or suggestions, contact info@smithy.com

While every precaution has been taken in the preparation of this manual, Smithy Co. shall not have any liability to any person or entity with respect to any loss or damage caused or alleged to be caused directly or indirectly by the instructions contained in this manual. Please see section on warranty and safety precautions before operating the machine.

Printed and bound in the United States of America.

Table of Contents

Inventory Check List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .i-iv

Chapter 1: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

Chapter 2: Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1

Chapter 3: Knowing Your Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1

Chapter 4: Caring For Your Machine . . . . . . . . . . . . . . . . . . . . . . . . .4-1

Chapter 5: Basic Parts of the MI-1220 XL . . . . . . . . . . . . . . . . . .5-1

Chapter 6: Uncrating and Setting Up the MI-1220 XL

Moving the machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-1

Uncrating and Positioning the machine . . . . . . . . . . . . . . . . . . . . . .6-1

Millhead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-2

Tailstock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-2

Three Jaw Chuck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-2

Selecting Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-4

Cleaning and Lubricating the MI-1220 LTD . . . . . . . . . . . . . . . . . . . .6-4

Oiling the Headstock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-5

Oiling the Ways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-5

Oiling the Carraige . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-5

Oiling the Tailstock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-6

Oiling the Apron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-6

Oiling the Leadscrew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-7

Oiling the Compound Angle Toolpost . . . . . . . . . . . . . . . . . .6-7

Setting Up Your MI-1220 XL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-8

Setting Lathe and Mill Speeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-8

Adjusting Belt Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-9

Adjusting Gibs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Reducing Backlash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-11

Crossfeed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-11

Longfeed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Running in the MI-1220 XL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Chapter 7: Turning

Turing Speeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-2

Gear Ratios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

Chapter 8: Metalcutting Theory

Tool Sharpness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-2

Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-3

Chapter 9: Grinding Cutter Bits for Lathe Tools

High Speed Steel Cutters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1

Materials Other than Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-3

Bits for Turning and Machining Brass . . . . . . . . . . . . . . . . . . . . . . . .9-4

Special Chip Craters and Chipbreakers . . . . . . . . . . . . . . . . . . . . . . .9-4

Using a Center Gauge to Check V-Thread Forms . . . . . . . . . . . . . .9-4

Acme or Other Special Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-5

Carbide-Tipped Cutters and Cutter Forms . . . . . . . . . . . . . . . . . . . . .9-5

Chapter 10: Setting Up Lathe Tools

Cutting Tool Height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-1

Turning Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-1

Threading Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-2

Cutoff, Thread Cutting and Facing Tools . . . . . . . . . . . . . . . . . . . . .10-3

Boring and Inside Threading Tools . . . . . . . . . . . . . . . . . . . . . . . . .10-3

Chapter 11: Setting Up with Centers, Collets and Chucks

Centering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-1

Centering a Round and Rectangular Steels . . . . . . . . . . . . . . . . . .11-2

Mounting Work between Centers . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Using a Clamp Dog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-4

Setting Up Work on Mandrel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-6

Steady Rest and Follow Rest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-6

Setting Up Work in a Chuck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-8

Mounting Work in a Four-Jaw Independent

Lathe Chuck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-8

Mouting Work in a Three-Jaw Universal Chuck . . . . . .11-10

Collet and Collet Attachements . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-11

Toolpost Grinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12

Chapter 12: Lathe Turning

Rough Turning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-1

Finish Turning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-2

Turning to Shapes

Machining Square Corners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-3

Taper Turning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-4

Boring a Tapered Hole

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-6

12-2

Chapter 13: Lathe Facing and Knurling

Facing Across the Clutch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1

Knurling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-2

Chapter 14: Changing Gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-1

Chapter 15: Cutting Screw Threads

Threading Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-1

Cutting Right Hand Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-3

Cutting Left Hand Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-4

Cutting Multiple Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-4

What Not To Do When Cutting Threads . . . . . . . . . . . . . . . . . . . . .15-5

Finishing Off a Threaded End . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-5

Cutting Threads on a Taper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-5

Chapter 16: Lathe Drilling and Boring

Reaming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16-1

Boring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16-2

Cutting Internal Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16-4

Cutting Special Form Internal Threads . . . . . . . . . . . . . . . . . . . . . .16-5

Chapter 17: Cutting Off or Parting with a Lathe . . . . . . . . .17-1

Chapter 18: Milling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18-1

Chapter 19: Workholding

Mounting to the Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19-1

Using a Vise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19-1

Dividing Heads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19-2

Rotary Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19-2

Chapter 20: Holding Milling Cutters

Arbors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20-1

Collets and Holders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20-1

Adaptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20-2

Chapter 21: Milling Cutters

End Mill Cutters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21-1

Plain Milling Cutters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21-3

Side Milling Cutters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21-3

Inventory Check List

It is a good idea to take inventory of the parts of your machine soon after it is unpacked. By doing so, you can quickly determine if any parts are missing. In addition, should you find it necessary to return the machine to Smithy for any reason, the inventory will ensure that all the parts you received have been returned. It is also good to take a look at the inventory before you operate the machine so that you can be familiar with the names of all the parts of your Smithy machine.

q Dead Center, MT3

Item #: 41-003 Quantity 1

q Dead Center, MT4

q Allen Wrench, 4mm

Item #: C30540 Quantity 1

rench, 5mm

q Al

len W

Item #: C30542 Quantity 1

q Dri

Item #: 41-004 Quantity 1

ll chuck, 1/2”

Item #: 72-001 Quantity 1

q Al

len Wrench, 6mm

Item #: C30537 Quantity 1

len Wrench, 8mm

Item #: C30536 Quantity 1

q Wrench, 14 mm

Item #: 81-500 Quantity 1

q Arbor

, JT33-MT3

ang)

(No T Item #: C30523 Quantity 1

q Drift, MT2

Item #: C30558

y 1

Quanti

q Gear, 32 Teeth

Item #: C30145 Quantity 2

q Gear, 33 Teeth

Item #: C30146 Quantity 1

eeth

q Gear

, 39 T

Item #: C30148 Quantity 1

eeth

, 40 T

Item #: C30149 Quantity 1

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Midas 1220 XL Operator’s Manual

q G

ear, 42 Teeth

Item #: C30150 Quantity 1

q Gear, 45 Teeth

Item #: C30156 Quantity 1

q Gear, 48 Teeth

Item #: C30151 Quantity 1

q Gear, 49 Teeth

Item #: C30152 Quantity 1

q Gear, 50 Teeth

Item #: C30153 Quantity 1

q Gear, 56 T

Item #: C30157 Quantity 1

q Gear, 60 T

Item #: C30159 Quantity 1

eeth

q G

ear, 63 Teeth

Item #: C30160 Quantity 1

q Jaws (3), 5”

Item #: 9-10 Quantity 1 set of 3

q Key, Lathe Chuck

Item #: C30532 Quantity 1

q K

ey, Drill Chuck

Item #: C30533 Quantity 1

q Open End Wrench,

8/10mm Item #: C30539 Quantity 1

q Open End W

17/19mm Item #: C30535 Quanti

rench,

ty 1

q Gear, 70 Teeth

Item #: C30202 Quantity 1

Gears on the machine:

q Gear, 27 Teeth

Item #: C30143 Quanti

ty 2

q Gear, 30 Teeth

Item #: C30144 Quantity 1

q Gear, 60 Teeth

Item #: C30159 Quanti

ty 1

q Adapter Precision

End Mill Item #: 65-010 Quantity 1

q End Mill Single

4 FHS Item #: 50-402 Quantity 1

For Assistance: Call Toll Free 1-800-476-4849

S 3/8 1/4”

Inventory Checklist

q E

nd Mill Single

4 FHSS 3/8 3/8” Item #: 50-406 Quantity 1

q End Mill Single

4 FHSS 3/8 1/4” Item #: 50-410 Quantity 1

q T-Slot Nut, 7/16”

Item #: 35-105 Quantity 2

q W

asher,

Anti-Back Lash Shim Item #: 82-050 Quantity 3

q Vise, Bracket Bolt

3/8 x 1-1/4” Item #: 36-610 Quantity 2

q Plug, Drill Chuck Arbor

Item #: S12898 Quantity 1

q Air Mask

Item #: 15-020 Quantity 1

q Goggles

Item #: 15-015 Quantity 1

q Ear Plug

Item #: 15-025 Quantity 1

wbar

q Dr

3/8 x 16 x 14” Item #: 75-A Quantity 1

q Nut, 3/8 16

Item #: 7-6 Quantity 1

q Vise, 0-90 Degrees

Adjustable Angle 3-1/4” Jaw Item #: 32-110 Quantity 1

q Carbide Bit Set

Item #: 43-000 Quantity 1

q Machine Tool

asics (DVD)

B Item #: 12-004 Quantity 1

q Cutting Fluid/ Tapping

Item #: 49-101 Quanti

ty 1

q Washer,

Flat 5/16” Item #: 7-8

y 1

Quanti

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iii

Midas 1220 XL Operator’s Manual

q O

perator’s Manual

Item #: 83-949 Quantity 1

q 5

” 3 Jaw Chuck

Part # C30532 Quantity 1

q Manual Cover

Item #: 83-942 Quantity 1

q Oil Can

Part # 80-100 Quantity 1

q Compound

Angle Toolpost

Part # 45-110 Quantity 1

Missing Items?

If you find that an item is missing or defective from your Quick Start Tool Pack

Call Us TOLL FREE 1-800-476-4849

or send an e-mail to info@smithy.com

within 30 days of receiving your machine so that we may assist you immediately. Our sales and service technicians are available 8am to 5pm ET, Mondays to Fridays.

For Assistance: Call Toll Free 1-800-476-4849

Chapter 1

Introduction

Congratulations on purchasing a Smithy Midas 1220 XL lathe-mill-drill. We are pleased you chose Smithy to fulfil your machining needs.

The purpose of this manual is to give the machinist, beginniner or advanced, the information he needs to operate the Smithy Midas 1220 XL. It will teach you about the machine's parts and how to care for them. In fact, education is our primary goal. We'll explain how to grind cutters, set up lathe tools, hold workpieces, and do all basic machining operations.

Please read this operator's manual carefully. If you don't understand how your machine works, you may damage it, your project, or yourself. If you want to learn more about machining practices, Smi experience. We also suggest using your local library as a resource. Enrolling in a machining class will give you the best knowledge of machining.

If you have any questions not covered in this operator's manual, please call Smithy Co.

ained technicians wi

Our tr can reach them by dialing 1-800-476-4849 Monday through Friday, 8:00 am to 5:00 pm Eastern time.

thy offers books that meet the needs of machinists at all level of

ll help you with any machining problems you may have. You

We are always interested in your suggestions to improve our products and services. Feel free to contact us by phone or in writing. If you have comments about this operator's manual, or if you have a project you'd like to share with other Smithy owners, contact the Communications Dir

We look forward to a long working relationship with you. And thank you again for putting your trust in Smithy.

ector

thy Co

, Smi

., PO B

ox 1517, Ann Arbor, MI48106-1517.

Customer Information

This manual should remain with your Smithy machine. If ownership changes, please include the owner's manual with the machine.

Model # ________________________________________ Serial #_________________________________________

(on the back of the lathe bed)

Purchase date ___________________________________ Delivery date ____________________________________ Sales Technician__________________________________

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Chapter 2

Safety

Your workshop is only as safe as you make it. Take responsibility for the safety of all who use or visit it. This list of rules is by no means complete, and remembers that common sense is a must.

1. Know your machine. Read this manual thoroughly before attempting to operate your lathe-mill-drill. Don't try to do more than you or your machine can handle. Understand the hazards of operating a machine tool. In particular, remember never to change speeds or setups until the machine is completely stopped, and never to operate it without first rolling up your sleeves or tying them at your wrists.

2. Ground the machine. The Midas 1220 XL has a three conductor cord and a three pronged gr grounding the machine.

3. Remove all adjusting keys and wrenches from the machine before operating. A chuck key or misplaced Allen wrench can be a safety hazard.

ounding type receptacle. Never connect the power supply without properly

4. Keep your work area clean and organized. Cluttered work areas and benches invite accidents. Have a place for everything and put everything in its place.

5. Keep children away from the machine while it is in use. Childproof your shop with padlocks, master switches, and starter keys, or store the machine where children do not have access to it.

6. Wear appropriate clothing. Avoid loose fitting clothes, gloves, neckties, or jewellery that could get caught in moving parts. If you have long hair, tie it up or otherwise keep it out of the machine.

y glasses, goggles, or a face shield at all times. Use glasses designed for

7. Use saf machinery operation; regular glasses will not do. Have extras for visitors. Know when to wear a face mask and earplugs, as well.

8. Check for damaged parts. Make sure the machine will run properly before operating it.

9. Disconnect the machine before servicing and when changing accessories. Shut power

off before making changes, removing debris, or measuring your work. Don't reach over the machine when i

10. Avoid accidental starts. Turn the switch to Off before plugging in the machine.

t's oper

ating. K

ou hands out of the w

eep y

11.Secure your work. Flying metal is dangerous. Loose work can also bind tools.

12. Use the r

out.

ecommended ac

2-1

cessories. Understand how to use them bef

For Assistance: Call Toll Free 1-800-476-4849

e trying them

13. Use the correct tool for the job. Don't try to make a tool into something it isn't.

14. Keep your mind on your work.

Pay attention to these simple rules and you will spend many safe, enjoyable hours in your workshop.

Remember: Your safety largely on your practices. Modifying your machine may void the warranty and create potential hazards.

Safety

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Chapter 3

Knowing Your Machine

The Midas 1220 XL has a 3/4 hp, 110 V motor. The motor powers the lathe and millhead through the main belt drive and the mill/drill belt drive.

A positive lock clutch in front of the spindle pulley transfers power to either the lathe or the mill. The clutch has three positions. To power the lathe, pull the clutch handle out. To power the mill, push the clutch all the way in. The middle position is neutral. Always shift the clutch with the motor turned off.

The Smithy can use V-belts or round polyurethane belts. The latter produce less dust and is easier to change than standard V-belts.

The lathe runs at six speeds from 160 to 1600 rpm. To change lathe speeds, adjust the belts in the main belt-drive system. This system uses three pulleys: the motor pulley, floating idler pulley and spindle pulley.

To run the lathe at lower turning speeds, use two belts. Install one between the motor and idler pul speed, move the spindle belt in two more positions on the pulleys.

leys and the other between the idler and spindle pul

leys. To increase the

For higher ranges, use one long belt from the motor pulley directly to the spindle pulley. You can adjust this belt to three different positions on the pulleys.

The millhead also has a belt-drive system. It uses only one belt, adjustable to either the top or bot belt drive, let you select 12 speeds ranging from 125 to 1600 rpm for milling or drilling.

tom posi

tion on the pul

leys. These two positions, in conjunction wi

th the main

3-1

For Assistance: Call Toll Free 1-800-476-4849

Chapter 4

Caring For Your Machine

The Midas 1220 XL is a delicate, precision tool with ground ways and hand-scraped bearing surfaces under the table and carriage. Any rust spot or battering of the ways, any chips or grit between close fitting parts, will affect the accuracy of this fine tool. Follow these guidelines whenever you use your Smithy machine.

When you finish working, wipe machined surfaces with a clean, oily rag. Never leave the machine without this thin film of protective oil over all parts that might rust, especially ground finished parts.

Never lay wrenches, cutting tools, files, or other tools across the ways of your lathe. The slightest dent or burr could impair its accuracy.

ore inserting collars, centers, adapters, or drawbar attachments in either the spindle

Bef or tailstock spindle, wipe them with a clean, oily rag. Also wipe all internal surfaces carefully with an oily rag on a ramrod. Chips or dirt on the centers or in the spindle nose can scratch or mar surfaces and interfere with the assembled part's alignment.

Lubricate the machine befor

e each use (see Section 6.4)

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Chapter 5

Basic Parts of the MI-1220 XL

To learn the operations of your machine, you have to know the names and functions of its basic parts.

Figure 5.1 Basic parts of the MI-1220 XL

Bed

- The B for absolute rigidity. The two ways on the top are the tracks on which the carriage and tailstock travel. To maintain an exact relationship between toolpoint and workpiece from one end of the machine to the other aligned to the line of centers and to one another.

5-1

ed (Figure 5.1) is the machine's foundation. It is heavy, strong and built

ys must be absolutely true and ac

, the w

For Assistance: Call Toll Free 1-800-476-4849

cur

ately

Basic Parts of the MI-1220 XL

Carriage

- The carriage consists of the saddle and apron. It moves by hand or power along the bed, carrying the cross slides, compound rest, and toolpost. Its function is to support the cutting tool rigidity and move it along the bed for different operations. It locks into place by tightening the carriage lock under the cross slide handwheel.

Change Gears

- The change gears cut different thread pitches. They also determine the feed rate. Five change gears come installed on the machine; others are packed with it.

Figure 5.2 Your machine arrives with this gear configuration. The C gear, behind B

meshes with D. Note the top two gears are permanent.

Compound Rest

- Mounted on the cross slide, the compound rest swivels to any angle horizontal to the lathe axis to produce bevels and tapers. Cutting tools fasten to a toolpost on the compound r

est. The calibrations on the front of the base are numbered

in degrees from 60 degree right to 60 degree left.

Cross Slide

- The T

-slotted cross slide (Figure 5.1 and 5.3) moves crosswise at 90 degree to the lathe axis by manual turning of the cross-feed screw hand-wheel. It also serves as the milling table.

Gib Adjustment

Screws

Saddle

Gib Adjustment

Screw

Cross Slide

Lock

Cross Slide Handwheel

Figure 5.3 The cross slide moves laterally when you turn the cross slide handwheel.

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Midas 1220 XL Operator’s Manual

Drill Press and Fine Feed Clutch

- Pushing in the drill-press clutch engages the fine feed. To work the clutch, release the spring tension by rotating the drill-press handles clockwise. Pull the clutch out to use it as a drill press or push it in to the fine feed. Use the fine-feed handwheel to move the quill up and down.

Forward / Off / Reverse Switch -

This is the main switch used to operate the lathe. It is simply a forward / reverse switch for the motor. The motor turns counter clockwise for normal lathe operation and clockwise for normal milling and drilling.

Gearbox

- The gearbox (Figure 5.1 and 5.4) houses the belts that drive the spindle and change gears for the powerfeed. Select the thread pitch (for threading) or the feed rate (for turning) by changing the four change gears on the right side of the gear box.

Figure 5.4 The gearbox houses the belts and change gears.

Half-nut Engagement Lever

- This lever, located on the apron, transmit power to

the carriage when rotated 90 degrees to the right.

10.

Half-nut Speed Selector

- The two-speed selector for powering the leadsrew is on

the front of the headstock. The leadscrew turns twice as fast in the II position as in the

tion.

I posi

11.

Headstock

- The headstock, which is secured to the bed, houses the gears that drive

the powerfeed and the taper bearings that secure the lathe spindle.

12.

5-3

Lathe Belt Tensione

d to tighten the bel

handle f

orw

r - To adjust the lathe belt (Figure 5.5), pull the tensioner

t, back to loosen i

For Assistance: Call Toll Free 1-800-476-4849

Basic Parts of the MI-1220 XL

Figure 5.5 To adjust the tension on the lathe belt, move the tensioner handle forward or back.

13.

Lathe / Mill / Drill Clutch

- The lathe/mill/drill clutch (Figure 5.4) are inside the gearbox. A three-position clutch, it transfers power to either the lathe or the mill, but not to both at the same time. T

o engage i

t, rotate it slowly while pushing or pulling on the clutch sleeve. Pulling it to the left runs the lathe, to the right (all the way in) runs the mill/drill. The middle is neutral.

14.

Lathe Spindle

- The end of the lathe spindle face in the tailstock is the spindle nose. The spindle nose, which has an MT4 taper, rotates the workpiece and drives lathe chucks and other work holding devices. All attachments such as three and four jaw chucks bolt to the spindle flange ei

15.

Leadscrew

for lathe turning or thread cut

ther directly or via an adapter plate.

- The leadscrew, which runs the length of the bed, moves the carriage ting. It works both manual

ly and under power. You can also

use it manually with the mill.

16.

Locks

- Locks on the cross slide (Figure 5.3) carriage (Figure 5.1), quill (Figure 5.6), and tailstock (two), Figure 5.1 and 5.7, keep them from moving. During machining, lock all lock except the one on the part you want to move.

Figure 5.6 The quill moves in and out of the millhead, carrying the spindle.

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Midas 1220 XL Operator’s Manual

17.

Micrometer Dial Collars

- Just inside the handles of the tailstock (Figure5.1), crossfeed (Figure 5.1), drill press (Figure 5.1), compound feed (Figure 5.1), and leadscrew (Figure 5.1) there are collars calibrated in inches. The compound feed, leadscrew, and crossfeed are calibrated in two thousandths, the tailstock in thousandths, and the drill press in 40-thousandths.

These micrometer dial collars can move independently around the handle shafts. This independent motion is called float. Floating dials on the cross slide, tailstock, and leadscrew let you zero the collars at any point and read the feed travel from that point on the dial for added accuracy.

18.

Mill Belt Tensioner -

To adjust the mill belt (Figure 5.7), swing the roller assembly to the front and place the belt on the back of the roller. Loosen the roller assembly and slide it back and forth in its slot.

Figure 5.7 With the millhead cover off, you can adjust the mill-belt tension.

19.

Millhead Height Adjustment

- Unlock the mi

ll-head lock and place the height adjustment handle in one of the three holes in the black collar. Turn the collar to raise and lower the millhead.

20.

Mill Spindle

- The mill spindle (Figure 5.7) attaches to the quill, which moves in and out of the head. The quill lock keeps the quill still when you install or remove tools from it and while milling horizontally. Usually, tools fit into collets that attach through the

wbars.

spindle via dr

21.

Tailstock

- The tailstock, which provides right-end support for the work, moves along the bed and can stop at any point. It has an MT3 taper and holds centers, drills, reamers, taps and other tools. To move the tailstock spindle, turn the tailstock hand wheel.

To offset the tailstock, adjust the two base-locking bolts (Figure 5.8). To offset to the left, loosen the left adjusting bolt and tighten the right. To offset to the right, loosen the right adjusting bolt and tighten the left.

5-5

For Assistance: Call Toll Free 1-800-476-4849

Tailstock Setover

Screw

Right Tresle

Setscrew

Basic Parts of the MI-1220 XL

Tailstock Base-

Locking Bolts

Figure 5.8 To offset the tailstock, adjust the base-locking bolts.

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Chapter 6

Uncrating and Setting Up The MI-1220 XL

Moving the Machine

Moving a machine tool can be dangerous. Improper techniques and methods may injure you and/or damage the machine. To find a professional to move and site your Smithy machine to look in your local Yellow Pages under “Machine Tools, Moving and/or Rigging.” If there is no such listing or your community does not have a rigging specialist, a local machine shop or machinist may be able to provide a referral.

When you pick up the machine at the shipping terminal, bring a crowbar, tin snips for cutting the metal straps, and a hammer. If there is obvious shipping damage to the crate, you'll be able to inspect the machine before signing for it. Note any damage on the bill of lading (shipping document). Fill out the claims form and notify both Smithy Co. and the shipping terminal about the damage. Failure to notify both parties can complicate and/or invalidate a claims process.

Trucking compan ient to transport the machines in trucks wi

y terminals usually have forklifts to assist customers. It's most conven-

thout canopies and lar

ge vans.

Uncrating and Positioning the Machine

The machine is assembled, inspected and ready to go on its stand when you receive it. It's wrapped in a water and greaseproof cover, strongly braced, and crated. A box of

cessories is also in the crate.

The metal bands ar under tension. Wearing eye protection and gloves, cut the metal bands with tin snips. Be careful- the cut edges are

. The band secur

sharp the base.

After removing the straps, lift off the crate top. Tip the crate from the tailstock end up and over the machine (Figure

6.1). Do not damage the cr need i machine.

t another time to transport the

ound the crate are

es the cr

ate top to

ate; y

ou ma

Figure 6.1 Tip the crate from the tailstock end up

and over the machine.

6-1

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Uncrating and Setting Up the MI-1220 XL

Now open the accessories box. Check the items in it against the accessory checklist. After accounting for all parts, you're ready to move your Midas 1220 XL into its work position.

Four men can move the Midas 1220 XL using the four lifting handles (Figure 5.1). You can reduce the weight so two people can move it by following these instructions:

Millhead

1. Remove the four hexagon socket-head capscrews at the base of the millhead support

column (Figure 6.2). If a screw runs through the belt box into the flange of the support column, remove it too.

Figure 6.2 Remove the millhead and column from the lathe head.

2. Lock the millhead locking handle (Figure 5.1)

3. Lift the millhead and column off the lathe head (Figure 6.2). You may have to rock it

back and forth while lifting it.

Tailstock

1. Loosen the tai

gib and the locking pin will fall out. Be careful not to lose them.

lstock locks (Figur

e 5.1) and pull the tailstock off the end of the bed. The

Three-jaw Chuck

ts behind the chuck that hold it to the spindle flange (Figure 6.3).

e the thr

emo

1. R The chuck will come off. Place a board between the chuck and ways to protect the ways.

ee bol

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Midas 1220 XL Operator’s Manual

Bolts

Figure 6.3 The chuck attaches to the spindle flange with three bolts. The one bolt located on the other side of the spindle does not show.

Put the machine on a str

ong, rigid table 40” long x 24” wide x 28 – 33” high. We recommend you bolt down the machine using the holes in the base of the bed or using the lifting handles the same way they held the machine to the shipping pallet.

Caref

ly lift the machines b

y the handles, move it over the stand, and lower it into position. Do not let any part of your body come between the machine and the stand. Bolt the machine to the stand, using one flat washer and one lockwasher per bolt.

Before permanently anchoring the machine, you may want to level the bed (Figure 6.4). The bed is rigid and supports itself, but having a level bed simplifies many setup operations. Use a pr

ecision level, both along and acr

oss the bed (Figure 6.5). Shim up any low points with sheet metal or other noncompressible material. After tightening the anchor bolts, check the bed again.

Figure 6.4 Check along and across the bed to make sure it is level.

6-3

For Assistance: Call Toll Free 1-800-476-4849

Uncrating and Setting Up the MI-1220 XL

Figure 6.5 To check bench and bed level accuracies, successively place level at A, B, C, D

(longitudinal positions) and E and F (transverse position). Bedways alignment in the

longitudinal plane should be better than 0.0016/40” ; alignment in the transverse

plane should be better than 0.0024/40”.

Selecting a Location

There are several major considerations when selecting a location for your Smithy:

1. Operation is from the apron side, so allow at least 40 – 48” clearance in front of the machine.

2. The machine should be on a 30amp circuit and close to the power outlet. If you must use an extension cor

d, check wi

th an electrician to make sure the cable can handle the

electrical load.

3. Provide ample working light over the operator's shoulder.

4. Place the machine on a solid foundation-concrete, if possible. If the floor is wood, make

e it can support the machine and workbench. Brace it if necessary to prevent sagging

sur or settling.

5. Make allowances at the back of the machine tool, at the end, and above it for later additions, attachments, and/or accessories. Provide clearance on the left end for bar stock to be fed through the spindle. If you are considering placing more than one machine in an area, allow enough floor space to feed long bar stock to each machine.

Cleaning and Lubricating the Machine

Smithy machines are shipped with a protective grease coating. To remove it, spray on

or a few minutes, and wipe it off with rags. Use a brush and

t f

WD-40, let i noncorr

t si

e kerosene or white mineral spirits to clean hard to reach places.

osiv

Give special attention to the leadscrew. Use a brush or cotton string to clean down into the threads.

The best w

ay to clean the powerfeed gears is to remove them completely. wipe the

pulleys with a damp rag.

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Midas 1220 XL Operator’s Manual

Once it's cleaned, your Smithy is ready for lubricating. Do this carefully and thoroughly before starting the machine. Use pressure oil can and good quality SAE No. 20 or 30 weight machine oil on the bearings and headstock.

To be thorough and complete, follow this routine:

Oiling the Headstock

1. Open the gearbox door to expose the change gears. Oil the button in the casting

behind the D gear (Figure 6.6). Then put a few drops of oil on the teeth of all the gears. Grease the zerk on the A gearshaft.

Figure 6.6 Oil the button behind the D gear.

2. Check the sight glass under the chuck. If necessary, add oil until it is half full. The oil-

ll plug is at the back of the headstock above the motor (Figure 5.5). Be careful no to

fi overfill it. If you have to top it with oil, pour in only an ounce at a time and wait to see

esults in the sight glass. Too much oil will make the motor lug and sling oil from

the r behind the chuck and inside the belt box.

Oiling the Ways

un the carriage as far to the left as possible. Put a few drops of oil on the ways. Run

1. R the carriage to the extr cially formulated for ways.

eme right and r

epeat. You may want to use Way-lube, an oil spe-

Oiling the Carriage

tons in the cr

1. Lubricate the oi the front of the cross-slide ways.

l but

ide table (Figur

oss-sl

e 6.7). There are two buttons on

6-5

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Uncrating and Setting Up the MI-1220 XL

Figure 6.7 Oil the buttons (circled) along the cross-feed table and cross slide.

2. Put a few drops of oil on the compound and cross-slide feedscrews.

ops of oil on the compound slides.

3. Put a f

ew dr

Oiling the Tailstock

1. Oil the buttons on top of the tailstock (Figure 6.8)

Figure 6.8 Oil the two buttons on the top of the tailstock.

Oiling the Apron

1. Put oil in the button just behind the cross-slide handwheel (Figure 6.7).

2. Put oi

l in the but

ton at the back of the cr

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oss-slide (Figure 6.7).

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Midas 1220 XL Operator’s Manual

Oiling the Leadscrew

1. Put oil in the oil buttons in the left trestle.

2. Put oil in the support for the right end of the leadscrew (figure 6.9).

Figure 6.9 Oil the support for the right end of the leadscrew.

3. Put a few drops of oil along the leadscrew and feed shaft.

Oiling the Compound

1. Put oil in the two buttons on the top.

Oiling the Mill/Drill Clutch

1. Put oil in the button on top of the clutch housing (Figure 6.10).

Figure 6.10 Oil the clutch-housing button.

To keep your machine in peak condition, lubricate it daily after removing any debris.

6-7

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Uncrating and Setting Up the MI-1220 XL

Setting up Your MI-1220 XL

The Midas 1220 XL comes with all major components assembled, but it is not ready to use right out of the crate. Do not start the motor until you correct the positions of the cross slide and leadscrew handwheels (Figure 5.1). We reversed these handles at our warehouse to protect them during shipment. A drop or two of oil on the shafts will help the handles slide on. Starting the motor with these handles in their shipping positions will damage the machine's gear, bearings, and handles. You must also install the tailstock handwheel, two drill-press handles, millhead lock handle and millhead height adjustment handle.

Setting Lathe and Mill Speeds

Changing belts changes lathe speeds. The lower speeds use the two short belts. There is only one position for the motor pulley to idler pulley belt. It goes on the smallest sheave of the motor pulley (behind the largest sheave, Figure 6.11) and on the largest sheave of the idler pul smallest sheave of the idler pulley to the largest sheave of the spindle pulley (position C). Move it in one sheave for 250 rpm (position D) and one more for 400 rpm (position E).

ley. For 160 rpm, set the idler pulley to the lathe spindle pulley belt on the

LOW HIGH

C D E

F G H

C 160

D 250

E 400

F 630

G 1000

H 1600

Table 6.1Setting Lathe speeds (RPM)

or the higher speeds, r motor pulley to the spindle pulley. For 630 rpm (position F), run the belt from the outside sheave (closest to the door) on the motor pulley to the largest sheave on the spindle

ve it in one sheave for 1000 rpm (position G). For 1600 rpm (position H), run

. Mo

ley

pul

rom the largest motor pulley sheave to the smallest spindle pulley sheave.

t f

emove the two small belts and use the single long belt from the

Set mill speeds using various combinations of the lathe belts and the belt on top of the millhead. For 125 rpm, place the mill belt in position A and the lathe belts in position C (Figure 6.12). For 160 rpm, place the mill belt in position B and the lathe belts in

tion C, etc.

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Midas 1220 XL Operator’s Manual

321

A4 X B1

B4 C1

315

A3 X B1 B3 C1

630

A2 X B3 B2 C3

1250

A4 X B2

321

B4 C2

A4 X B3

B4 C3

400

500

A2 X B1 B2 C1

A3 X B2 B3 C2

800

1000

A1 X B2 B1 C2

A1 X B3 B1 C3

1600

2000

Table 6.2 Setting Mill/Drill Speeds (RPM)

Adjusting Belt Tension

To get maximum performance from your machine, keep the drive belts snug.

To adjust the tension on the mill belt, swing the roller to the front and place the belt on the back of the roller. Loosen the nut at the bottom of the roller and slide the roller in its shaft to the desir

ed posi

tion. Tighten the nut (Figure 5.7).

When you use only the single long belt, the spring at the bottom of the idler-pulley bracket holds the idler pulley so it does not fall onto the motor pulley. To adjust the tension on the spring, loosen the pivot shaft (Figure 6.11) and tighten or loosen the spring as needed. Then retighten the shaft.

Figure 6.11 Adjust the spring tension on the idler-pulley bracket.

6-9

For Assistance: Call Toll Free 1-800-476-4849

Uncrating and Setting Up the MI-1220 XL

To tighten the lathe belts, move the tensioner handle above the motor (Figure 5.5) so it points toward the lathe head. Turn the knurled knob clockwise to tighten the belt and counter clockwise to loosen it. If there is not enough adjustment, remove the pivot pin and turn the knob as needed. Then reattach the pin.

Adjusting the Gibs

The Midas 1220 XL has straight gibs. Before using the machine, adjust the gibs to compensate for wear and maintain the proper fit between sliding surfaces. Gib adjustment affects cutting tool rigidity and the machine's ability to make accurate cuts.

As the gibs tighten, the effort it takes to turn the handwheels increases. Adjust the gibs according to the work you are doing and personal preference. What's important is to adjust them evenly. The tighter the gib, the more accurate it will be. Removing and polishing the gibs also improves the tolerances.

Before beginning, make sure the ways are clean and well-oiled. You must also understand locks for the compound, cross slide, carriage, and tailstock act directly on the gibs for their locking power. Back these locks off completely.

Cross-slide gib

. Start adjusting the cross-slide gib with the table centered on the carriage. Back off all setscrews and jam nuts. Tighten the two inside setscrews all the way (Figure 5.3), locking up cross-slide movement. Then back off each setscrew one-quarter turn and check the movement. Finally, set the tension on the outer screws to match.

The effort it takes to move the table should be the same in both directions. if it is not, the gib is not adjusted evenly. If you feel more handwheel resistance when the cross slide is going away from you, the leading edge of the gib is too tight. Back off the setscrew closest to you a little to relieve the tension. If there is more resistance when the table is coming toward you, the leading edge of the gib is too tight, and you should adjust the

ew furthest from you. When everything is set, hold the setscrews carefully with the

scr Allen key and lock the jam nuts.

Carriage gib.

The carriage has only two gib-adjusting screws, accessed through holes

in the front of the apron (Figure 5.1). Start the adjustments as you did with the cross

y, then back them off one-quarter turn and test the

ide: tighten the scr

ting. Handwheel r

set

ews al

l the w

esistance should be ev

en in both directions.

The big difference between the cross slide and carriage is that the carriage gib travels with the carriage as it moves down the lathe bed. If you have more handwheel resistance when the carriage moves toward the tailstock, the leading edge of the gib is on the right

e moving the carriage. If you

side of the carriage, the same side as the dir

e more handwheel resistance when the carriage is moving toward the headstock, to

ection y

ou ar

left, release the tension a bit on the left-hand gib setscrew. As you work with the adjustments, you'll feel the difference even gib tension makes on the handwheels.

Compound gib

. The compound gib has two adjusting scr

For greater tool rigidity, you can adjust the compound gib a bit tighter that the others.

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ews and jam nuts (Figur

e 5.3).

6-10

Midas 1220 XL Operator’s Manual

Tailstock gib.

be free than the others so it is easier to position the tailstock. Again, the lock acts on the gibs. When tightened, it automatically brings the tailstock into alignment.

Figure 6.12 You can adjust the tailstock gibs with two scetscrews, one on each side

The tailstock gib also has two adjusting screws (Figure 6.14). This gib can

of the tailstock.

Reducing Backlash

Backlash of 0.008 – 0.015” as measured on the micrometer dials is normal. If you have more backlash than that, refer to the schematics at the back of this manual, if necessary, and follow these directions:

Crossfeed

1. Tighten the setscrew on the bottom of the screw seat so the bushing inside the screw

seat can not move.

2. Tighten the cap nut so the handwheel is secure.

3. Turn the handwheel one way, then the other. If a gap opens and closes between the

dial and screw seat, you must install one or more shim washers (ask a Smithy technician about our antibacklash shim w

To install shims, remove the handwheel, key, washer and the outer part of the dial and spring. Remove the inner hub of the dial. Install one or more shim washers between the bearing and the dial hub (Figure 6.13) and reassemble. Tighten the setscrew on the bottom of the screwseat as well.

asher ki

t # K99-190)

Figure 6.13 You can reduce handwheel backlash with a shim (left) or by tightening the

setscrew on the bottom of the screwseat (right). This locks the bush bearing

holds the screw and reduces any backlash.

6-11

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Uncrating and Setting Up the MI-1220 XL

Push and pull on the cross slide. If there is movement, remove the two bolts that attach the rear screwseat to the cross slide, remove the screwseat and screw the cross slide toward you until the screw comes completely out of the brass nut (Figure 6.14).

Figure 6.14 Adjust the tightening screws on the two-piece crossfeed nut to

reduce the backlash between the screw and nut.

Remove the brass nut and put one or two strips of shim stock in the side of the hole. The fit should be tight. Screw the cross slide back onto the carriage. Adjust the screws in the

ass nut to r

emove any play between the thread in the nut and screw. Reassemble the

screw seat onto the cross slide.

Longfeed

1. Tighten the setscrew on the bottom of the right trestle so the bushing is tight (Figure

5.7).

2. If there is still excess backlash, remove the cap nut, hand crank, and key.

3. Remove the washer, outer dial, spring and inner-dial hub key.

4. Install as many shim washer as possible between the bearing and dial. Then

reassemble.

Running In

Though al warehouse, it is wise to put your machine through a break-in run before starting to work. After oiling the machine, check the belts to make sure the tension is correct. Do not plug in the machine y

Follow these steps:

l Smi

thy machines are tested at the factory and again before shipping from the

et.

1. Set the lathe to 160 rpm.

2. Plug the machine into a gr

ounded 30 amp circuit.

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Midas 1220 XL Operator’s Manual

3. Start the motor by pushing in on the green button. To reverse the motor, push the red button to stop it, lift the cover over the rocker switch, and push the rocker switch either up or down to reverse the motor's rotation.

4. During the run-in, try the controls. Get a feel for your machine.

6-12

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Chapter 7

Turning

The lathe rotates a workpiece against a cutting edge. With its versatility and numerous attachments, accessories, and cutting tools, it can do almost any machining operation.

FPM 50 60 70 80 90 100 110 120 130 140 150 200 300

DIAM

1/16”

1/8”

3/16”

1/4”

5/16”

3/8”

7/16”

1/2”

5/8”

3/4”

7/8”

1”

1-1/8”

RPM

3056 3667 4278 4889 5500 6111 6722 7334 7945 8556 9167 12229 18344

1528 1833 2139 2445 2751 3056 3361 3667 3973 4278 4584 6115 9172

1019 1222 1426 1630 1833 2037 2241 2445 2648 2852 3056 4076 6115

764 917 1070 1222 1375 1538 1681 1833 1986 2139 2292 3057 4586

611 733 856 978 1100 1222 1345 1467 1589 1711 1833 2446 3669

509 611 713 815 917 1019 1120 1222 1324 1426 1528 2038 3057

437 524 611 698 786 873 960 1048 1135 1222 1310 1747 2621

382 458 535 611 688 764 840 917 993 1070 1146 1529 2293

306 367 428 489 550 611 672 733 794 856 917 1223 1834

255 306 357 407 458 509 560 611 662 713 764 1019 1529

218 262 306 349 393 426 480 524 568 611 655 874 1310

191 229 267 306 366 372 420 458 497 535 573 764 1146

170 204 238 272 306 340 373 407 441 475 509 679 1019

1-1/4”

1-3/8”

1-1/2”

1-5/8”

1-7/8”

2-1/4”

2-1/2”

2-3/4”

Table 7.1 Provides exact speeds (rpm). It does not make machine speed limitation into account. Determine the desired rate of speed and find the closest speed available on your machine.

153 183 216 244 275 306 336 367 397 428 458 612 918

139 167 194 222 250 278 306 333 361 389 417 556 834

127 153 178 204 229 255 280 306 331 357 382 510 765

117 141 165 188 212 235 259 282 306 329 353 470 705

102 122 143 163 183 204 224 244 265 285 306 408 612

2”

3”

95 115 134 153 172 191 210 229 248 267 287 382 573

85 102 119 136 153 170 187 204 221 238 255 340 510

76 91 107 122 137 153 168 183 199 214 229 306 459

69 82 97 111 125 139 153 167 181 194 208 278 417

64 76 89 102 115 127 140 153 166 178 191 254 371

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Midas 1220 XL Operator’s Manual

The modern lathe offers the following:

• The strength to cut hard, tough materials

• The means to apply power

• The means to hold the cutting point tight

• The means to regulate operating speed

• The means to feed the tool into or across, or into and across the work, either manually or by engine power, under precise control

• The means to maintain a predetermined ratio between the rates of rotating works and the travel of the cutting point or points.

Turning Speeds

When metal cuts metal at too a high speed, the tool burns up. You can machine soft metals like aluminum at fast speeds without danger or trouble, but you must cut hard steels and other metals slowly.

You must also consider the diameter of the workpiece (Figure 7.1). A point on a 3” diameter shaft will pass the cutting tool three times as fast as a point on a 1” diameter shaft rotating at the same speed. This is because the point travels a tripled circumference. For work in any given material, the larger the diameter, the slower the speed in spindle revolutions needed to get the desired feet per minute (fpm) cutting speed.

Lathes cut threads in various numbers per inch of material threaded, according to the operator's needs. The Midas 1220 XL cuts threads to metric or inch standards.

In thread cutting, the carriage carries the thread-cutting tool and moves by rotating the leadscrew (Figure 5.1). The basic principle is that the revolving leadscrew pulls the carriage in the desired direction and at the desired speed. The carriage transports the toolpost and the threading tool, which cut the thread into the metal being machined.

evolves in relation to the spindle, the coarser the thread. This

aster the leadscr

The f

ew r is because the threading tool moves farther across the revolving metal with each workpiece revolution.

The lathe spindle holding the workpiece revolves at a selected speed (revolution per

ding to the t

minute, or rpm) ac

cor

runs the length of the lathe bed, also r

ype and size of the workpiece. The leadscrew, which

olves at the desired rpm. There is a definite and

ev changeable ratio between spindle and leadscrew speeds. Figure 7.2 shows belt positions for various speeds.

7-2

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Gear Ratios

The lathe lets you use various indicated gear combinations to cut the desired number of threads per inch (tpi), or the metric equivalent, or to advance the tool at a specified amount each revolution (feed rate expressed as inches per revolution (ipr))

The Midas 1220 XL has a pick-gear gearbox (Figure 5.2); gears are picked and placed to change the gear ratios. The gearbox mechanism determines the leadscrew's rotation rate in relation to the spindle's for threading, turning and facing. To change the thread pitch (tpi), replace the gears per Table 7.2.

Turning

Threads Per Inch Metric Pitches

Speeds Gear Position Speeds Gear Position

1 2 A B C D

.003 .006 30 60 27 63

30 15 70 32 40 45

28 14 70 32 40 42

26 13 70 32 40 39

24 12 70 32 40 36

22 11 70 32 40 33

20 10 70 32 40 30

18 9 70 27 45 36

16 8 70 27 45 32

14 7 60 27 60 32

12 6 70 27 60 32

1 2 A B C D

0.50 1.00 49 32 42 56

0.60 49 32 45 50

0.70 49 32 42 40

0.75 1.50 63 32 42 48

0.80 49 50 60 32

1.75 49 48 63 32

1.00 2.00 63 32 49 42

1.25 2.50 60 32 49 32

1.50 3.00 63 32 56 32

Table 7.2 Gear Ratios

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Chapter 8

Metalcutting Theory

A machine tool is no more efficient than its cutting edge. Because lathe operations require continuous regrinding and resharpening of the machine's cutting tools, operators should know some metalcutting theory.

All cutting with a sharp edge, whether with the thin blade of a knife or the almost square edge of a closely supported carbide tool, is basically a wedging-apart action. The first essential of any wedging tool is a penetrating edge. The narrower the blade, the less force is needed to wedge it through the material. Therefore, when cutting comparatively soft materials with a cutting tool made from a much harder, stronger substance, the blade can be very thin and sharpened to a long, thin edge.

As the material hardness (or resistance to separation) increases, the strength of the cutting edge must also increase. A knife whose edge is too thin dulls quickly, even when cutting comparatively soft materials. This explain why, in Figure 8.1 the knife edge breaks off almost upon contact with the metal while the more obtuse cutting edge of a cold chisel stands up to continuous pounding.

Figure 8.1 The knife edge breaks off almost upon contact with the metal

because its cutting edge is not as strong as that of a cold chisel.

The primary requirements of the cutting edge of any metalcutting tool are that it be (A) strong and (B) closely supported. This understandable when we realize how much

e is exerted against the cutting edge. Pressure against cutting tools as

essur

d pr

down

eat as 250,000 per squar

While the workpiece revolves, a strong, rigidly held cutting edge is forced under its surface. As it presses down against the cutting edge, small chips or a continuous ribbon of metal wedges away (Figure 8.2). Only in soft, ductile materials is this wedging action continuous.

e inch (psi) ha

8-1

ve been measured on large metalcutting lathes.

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Metalcutting Theory

Figure 8.2 Wedging-off action in cutting hard steel. Note the false edge or crust

that builds up on the cutting edge.

On harder substances, the wedging force compresses, rises to the shearing point, and shears. Then it builds up and shears again, repeatedly. You can see this in the distortion of chips when cuts are heavy and materials hard.

When the shearing vibration synchronizes with the natural vibration period of any part of the tool, toolholder, or workpiece, chatter occurs. You eliminate chatter by changing one of the harmonizing f

actors: making the tool mor

e rigid, holding the cutter closer up in the toolholder, backing the toolholder farther into the toolpost, or altering the feed of the tool, operating speed of the lathe, or angle of the cutter bit to the workpiece.

Tool Sharpness

Instead of being the all important factor in determining tool performance, keenness of the cutting edge is just one of many factors. On rough or heavy cuts, it is far less important than strength, because a false cutting edge or crust usually builds up on the tool edge,

ts angle often increases the cutting tool's efficiency by

and though the edge dul increasing its wedging action. Cutter shape is usually more important than edges, which

ally are rough-ground and require honing for fine finishing cuts or work in soft,

gener ductile materials like brass or aluminum.

Lack of clearance, which lets a tool drag on the work below the cutting edge, is a break on the lathe, greatly reducing pressure on the cutting point and interfering with tool

ormance mor

perf

e than edge dul tool because of insuf use the tool on hard materials.

Clearance requirements change with almost every operation, but there are certain standards for all aspects of the cutting tool. You must not only provide clearance from the

ting edge; ther

cut minimum r

esistance across the top of the tool, it should often have top rake as well. You

e must also be end and side clear

determine the shapes and rakes to which you'll grind your tools by the tool holder you use. The Midas 1220 XL has a four-sided turret toolpost that accommodates up to four high-speed-steel (HSS), carbide-tipped, or indexable carbide turning tools.

ls, i

lness. A

t the same time, ex

ficient support to the cut

cessive clearance weakers a

ting edge. Such an edge will break off if you

ance. T

o help the chip pass with

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8-2

Midas 1220 XL Operator’s Manual

Heat

The energy expanded at the lathe's cutting point converts largely into heat, and because the energy is great, the heat is intense. Before today's HSS, carbide and ceramic tools, this heat created a serious machining problem. Machining could be done only under a steady flow of coolant, which kept the tool from heating to its annealing point, softening and breaking down.

With HSS, you can usually cut dry unless your machine is running at extremely high speeds on continuous, heavy-duty production work. HSS tools are self-hardening even when red hot. They do not dissipate the heat, however, or in any way prevent the workpiece from heating up. Because steel expands when heated, it is a good idea, especially with long shafts, to check the tightness of the lathe centers often and make sure workpiece expansion does not cause centers to bind.

In everyday lathe operations like thread cutting and knurling, always use cutting oil or other lubricant. On such work, especially if the cuts is light and lathe speed low, dipping a brush in oil occasionally and holding it against the workpiece will provide sufficient lubrication. For continuous high-speed, heavy-duty production work, however, especially on tough alloy steels, using a cutting oil or coolant will increase cutting efficiency. It's essential if you're using a non HSS cutting tool. When you use coolant, direct it against the cutting point and cutter. Consider installing a coolant system if you don't have one.

Low-Carbon

Speed (sfm)

Roughing

Finishing

Feed (ipr) Roughing

Finishing

able 8.1 l

T The f

ist cut

ormula is as follows:

High-

Steel

Carbon

Steel

Alloy Steel

Normalized

Aluminum

Alloys

Cast Iron Bronze

Annealead

120

0.010-0.202

0.003-0.005

Table 8.1 Cutting speeds and feeds for High Speed Steel Tools

ting speeds and f

50 65

0.101-0.020

0.003-0.005

eeds for HSS cutters so you can set up safe rpm rates.

45 60

0.010-0.020

0.003-0.005

200 300

0.015-0.030

0.005-0.010

0.010-0.020

0.003-0.010

70 80

100 130

0.010-0.020

0.003-0.010

rpm = CS x 4 / D”

whereCS = cut

the workpiece in inches.

ting speed in surf

8-3

eet per minute (sfm) and

ace f

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D” = diameter of

Metalcutting Theory

To use this formula, find the cutting speed you need on the chart and plug that number into the CS portion of the formula. After calculating the rpm, use the nearest or next-lower speed on the lathe and set the speed.

If you were to make a finish cut on a piece of aluminum 1” in diameter, for

example, you would see the desired sfm per Figure 8.3 is 300. Then

rpm = 300 sfm x 4 / 1

rpm = 1200 / 1

rpm = 1200 or next slower speed.

For high-carbon steel, also 1” in diameter,

rpm = 50 sfm x 4 / 1

rpm = 200 / 1

rpm = 200 or next slower speed.

With the four-turret toolpost, you can install all standard-shaped turning and facing tools

th 1” on smaller shanks. The centerline is appr

oximately 5/8” above the bottom of the turret. Smithy also offers quick-change tool sets that greatly speed up lathe operations. Contact a Smithy technician for details.

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8-4

Chapter 9

Grinding Cutter Bits for Lathe Tools

High-Speed-Steel Cutters

The advantage of HSS cutter bits is you can shape them to exact specifications through grinding. This lets you grind a stock shape into any form. Stock shapes come in an assortment of types, including squares, flats, and bevels. Many shops buy their cutters as ready-ground or ready-to-grind bits or blades.

Ready-to-grind bits and blades are of specially selected HSS, cut to length and properly heat-treated. They are fine tools in the rough and generally superior to HSS shapes sold by the pound.

ou have five major goals:

In grinding HS

• A strong, keen cutting edge or point

• The proper cutting form (the correct or most convenient shape for a specific

operation)

S cutter bi

ts, y

• Front clearance away from the toolpoint

• Clearance away from the side of the tool (side rake)

ee chip movement o

• Fr

Keenness angles can vary from 60° for mild softness to 90° for hard steels and castings (Figure 9.1).

Figure 9.1 Keenness angles vary from 60 to 80 degrees.

Front clear the edge weakens and breaks off (Figure 8.2). Side and back-rake requirements vary with the material used and operation performed. Back rake is important to smooth chip flow, which is needed for a uniform chip and good finish, especially in soft materials. Side rake directs the chip flow away from the point of cut.

ance must alw

ver the tool and away from the cutting edge.

Side

Rake

Side Clearance

3-10

ys be suf

ficient to clear the work. If it is too great, however,

Angle of

Keenness

9-1

For Assistance: Call Toll Free 1-800-476-4849

Grinding Cutter Bits for Lathe Tools

Figure 9.2 The edge weakens if front clearance is too great.

Grind cutters on a true-surfaced, good-quality, medium-grit grinding wheel (preferably an 8", 46-60A-grit or 68A-grit Carborundum wheel) at 6000 or 6500 rpm. When starting with an ungrounded cutter bit, the procedure (Figure 8.3) is usually to:

1. grind the left-side clearance

2. grind the right-side clearance

3. grind the end f

orm or r

adius

4. grind the end clearance

5. grind the top rake, touching in a chipbreaker.

If you are honing the cutting edge (for fine finishing or machining soft materials), draw the cutter away from the cutting edge across the oilstone as shown in figure 9.4.

Cutter Bit

Grinding Wheel

1. Left Side Clearance

2. Rigt Side Clearance

3. End

Clearance

4. Radius 5. Top Rake

Figure 9.3 Grinding sequence for an unground cutter bit.

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9-2

Midas 1220 XL Operator’s Manual

Oilstone

Figure 9.4 When honing, draw the cutter away from the cutting edge across the oilstone.

Materials Other Than Steel

As pointed out earlier, when grinding HSS cutters, we determine cutting angles primarily by strength requirements, not keenness requirements. Angles and rakes for general industrial shop use are established. In machining steel, the softer the steel, the keener the angle of the cutting edge. For soft steels, angles as acute as 61° are possible (Figure

9.5).

Figure 9.5 With soft steels, 61 degree angles are possible.

The same general rule applies to cast iron. Chilled or very hard cast iron requires tools with cutting-edge angles as great as 85°. For ordinary cast iron, you obtain greatest efficiency with a more acute cutting edge-approximately 71° (Figure 9.6).

Figure 9.6 With cast iron, a 71 degree angle is most efficient.

9-3

For Assistance: Call Toll Free 1-800-476-4849

Grinding Cutter Bits for Lathe Tools

Bits for Turning and Machining Brass

Brass tends to pull or drag when machined. It's best to machine it on dead center with the top rake in the horizontal plane of the lathe centers. Softer than steel, brass needs less support for the cutting edge. Brass cutters require an almost flat top angle and can gain greater angle keenness only in increased side and end rakes. It is often advisable to hone the cutting edges of cutters used to machine brass.

Note:

All roundnose cutters are ground with flat tops and equal side rakes because they

are fed across the work, to both right and left.

Special Chip Craters and Chipbreakers

When grinding cut-off blades, and occasionally on other cutter bits where the material's extreme hardness or toughness makes it difficult to control the chip leaving the work, it sometimes helps to grind a smooth, round crater just behind the cutting edge. This serves as a chip guide and starts the chip curl

ing smoothly (Figure 9.7).

Figure 9.7 A crater starts the chip curling smoothly.

Using a Center Gauge to Check V-Thread Forms

It may be convenient to grind a standard cutter bit for thread cutting, especially for cutting standard 60° V-threads. When grinding an ordinary square cutter into a thread

ting tool, tak

cut ordinary center gauge for a standard V-thread tool or a special thread gauge for special thread forms.

To grind a cutter for an ordinary V-thread, grind first the left side of the tool, then the right side, to 30°. Be careful to grind equally from both sides to center the toolpoint. Then

or true form by inserting the newly ground point in the closest-sized V in a standard

test f center gauge (Figure 9.8). Examine the gauge and cutter before a light. When the cutter is ground perfectly, no light streak shows between tool and gauge. Use a grinding chart for other r

e care to ensure a true thread form. The easiest way is to use an

es.

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9-4

Midas 1220 XL Operator’s Manual

Figure 9.8 Insert the point into the nearest seized V in the center gauge.

Acme or Other Special Threads

Thread gauges are available for all standard threads. Before grinding such cutters, ascertain the correct pitch angle of the particular thread profile. For example, the pitch of an acme thread is 29° to a side, and the toolpoint is ground back square to an exact thread profile that requires a different end width for each thread size.

Thread forms must be accurate if threads are to fit snugly and smoothly. Every resharpening of this type of cutter requires regrinding the entire form. It is far better, when doing any amount of threading, to use a threading tool with a special form cutter. Sharpening such cutters r profile.

es only flat, top grinding, which does not alter the cut

equir

ting

Carbide-Tipped Cutters and Cutter Forms

Carbide is a compound of carbon and a metal. In cutting tools, it is usually carbon and tungsten. The har carbides permi Bakelite, glass, and other difficult or "unmachinable" materials, its primary use in industry is f permit higher running speeds and much longer runs between resharpenings. The cutting edge of carbide tools stands up 10 to 200 times as long as the edge of HSS tools (Table

9.1).

The advantage of carbide is that it tolerates much higher heat than HSS or other alloys

ou can run at higher speeds. The disadv

so y must ha

or long pr

ve adequate support in the toolpost to prevent vibration and breakage.

dness of carbide cut

t easy machining of chilled cast iron, hard and tough steels, hard rubber,

oduction runs on ordinary steels. On such work, carbide-tipped tools

ting materials approaches that of diamond. Whi

antage is that i

t is more brittle than HSS and

9-5

For Assistance: Call Toll Free 1-800-476-4849

Grinding Cutter Bits for Lathe Tools

Application Use Grade

Cast Iron Roughing cuts C-1

Non-ferrous, non-metallic, high-temperature alloys

200 and 300 Series stainless steels

General purpose C-2*

Light finishing

Precision boring

Roughing cuts

General Purpose

C-3 C-4 C-5

C-6*

Alloy steels Finishing cuts C-7

400 Series stainless steel, high velocity Precision boring C-8

Table 9.1 Carbide Types and Cutting Tool Applications

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9-6

Chapter 10

Setting Up Lathe Tools

After selecting a cutter, insert it in the toolholder. Allow the cutter bit to project just enough to provide the necessary clearance for the cutting point. The closer the cutter is to the toolpost, the more rigid the cutting edge. Allen-head capscrews hold the tool in the toolpost. To assure maximum rigidity, don't let the tool extend too far beyond the end of the toolpost turret.

Cutting-Tool Height

After inserting the cutting tool into the toolpost, adjust the height of the cutting edge in relation to the lathe center. Insert a center in the tailstock. Then run the tool and center together

The cutting edge on the tool should meet the point on the center. It may be necessary to use shims, which can be of various thicknesses and materials (Figure 10.1). Man seasoned cutting-tool height machinists use pieces of old hacksaw blades as shims. If the toolbit is too high, shim the back of the toolbit. If it's too low, shim the entire tool.

Figure 10.1 Placing shims under the tool can correct cutting too height.

Turning Tools

For general turning operations, set the point of the cutter bit slightly above the centerline of the work. In steel, the harder the material, the less above center (Figure

10.2, left).

ceptions ar

Ex machining these materials, set the cut

10-1

e soft br

ass, aluminum, and materials that tend to pul

ter on dead center (Figur

For Assistance: Call Toll Free 1-800-476-4849

l or tear

e 10.2, right.)

. When

Setting Up Lathe Tools

Figure 10.2 The harder the steel (left),the less above center you set the cutter point.

For soft brass and aluminum (right), set the cutter on dead center.

When cutting toward the headstock on most turning and threading operations, swing the compound rest to hold the shank of the toolholder at an angle. The angle should be approximately 29-1/2° left of perpendicular to the line of centers, except for extremely heavy, rough-forcing cuts close to the limits. For such work, use a straight-shanked tool held perpendicular to the line of lathe centers in the right side of the toolpost. The tool will tend to swing out of the cut rather than hog into the work if you reach a stalling point (Figure 10.3)

Figure 10.3 The tool will swing out of the cut (left) rather than hog into the work (right) if

you reach a stalling point. Note the tool is in the right-hand side of the toolpost.

Threading Tools

Threading tools should always engage the work on dead center. Any deviation above or

ect the thread profile (Figure 10.4).

l af

below wi

Figure 10.4 Threading tools engage the work on dead center.

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Midas 1220 XL Operator’s Manual

Cutoff, Thread Cutting and Facing Tools

For cutoff, thread cutting, and facing, feed the cutter to the work on dead center (Figure

910.5). For the beginner, the average feed should not exceed 0.002 inches per revolution (ipr).

Chip Curve

Figure 10.5 Feed the cutter on dead center for cutoff, thread cutting and facing.

Boring and Inside Threading Tools

For boring and inside thr

10.6). For greater cutting efficiency, position the bar while parallel to the line of lathe centers sufficiently below center to give the cutter a 14-1/2 degree approach angle. For internal threading, grind the top face of the cutter to compensate for this angle, giving a flat, true f

Some machinists prefer to position the tool slightly above center when boring. With the bit abo workpiece.

orm top face.

ve center, if a tool chat

eading, the cutter point engages the work on dead center (Figure

ters it deflects down into empty space instead of into the

Figure 10.6 For boring and inside threading, the cutter point is at dead center.

10-3

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Chapter 11

Setting Up with Centers, Collets, and Chucks

Before setting work up on centers, make sure the spindle and tailstock centers align accurately. Do this by inserting a center into the nose spindle and inserting the tailstock center into the tailstock ram. Then move the tailstock toward the headstock until the centers touch (Figure 11.1). You can correct any lateral alignment error by adjusting the tailstock set over screws (Figure 4.8).

Figure11.1 When aligning spindle and tailstock centers, move the tailstock

toward the headstock until the centers touch.

For most turning operations, work is held in the lathe between the lathe centers b of holes drilled in the ends of the stock to be machined. Your machining accuracy depends primari Locating these holes is cal

ly on how precisely y

ou locate these holes at the center of the bar or block.

led centering.

y means

Centering

ou can impr

Y (Section 13.1). This gives you a true cross section in which to locate the centering holes.

1. First, chuck the stock in the appr

2. Place a right-hand side tool (or a straight turning tool with a facing cutter) in the

toolpost.

3. Car toolpost. If y and perhaps cause the center drill to run off center.

ove centering greatly by first squaring or facing the ends of the workpiece

otrude about an inch.

ly adjust the cut

ou don't do this, a smal

opriate chuck. Let the stock pr

ting edge so i

t or pr

l ti

t is exact

ojection wi

ly on center, then tighten it into the

ll remain in the center of the stock

4. Start your lathe on the slowest speed. Bring the tool into the cutting position against the center of the workpiece.

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Midas 1220 XL Operator’s Manual

5. Feed the tool from the center of the stock outward, toward yourself, using the hand crossfeed. One or two light cuts is usually enough to true up an end roughened by the hacksaw. After facing one end, reverse the work and face the opposite end.

Centering a Round and Rectangular Stocks

1.You can center on round stock (Figure 11.2) with calipers, dividers, or special

centering instruments (Figure 11.3). Centering square or rectangular stock is done by scribing lines from opposite corners. The intersection of these lines is the center (Figure

11.4).

Figure 11.2 Centering on round stock and

Figure 11.4 Centering on square or rectangular stock.

Figure11.3 Use centering instruments include calipers and dividers.

2. After locating the center of each end, driv

e a starting depr

ession f

or the dri

ll into the

stock with a center punch.

3. Check centering accuracy by placing the workpiece between the spindle and tailstock centers.

e the headstock slowly against the tip of a tool or a piece of rigidly held chalk.

olv

4. R

5. The chalk should touch just the high spots (Figure 11.5). If the center is off 0.002" or

more, correct the position of the center by repunching at an angle.

11-2

For Assistance: Call Toll Free 1-800-476-4849

Setting Up with Centers, Collets, and Chucks

halk Marks

Chalk

Compound

Figure 11.5 When you revolve the headstock against a piece of chalk,

The chalk should just touch the high spots.

6. Next, drill and countersink the centers to conform to the profile of the lathe centers. This is best done with a combination center drill/countersink held in the tailstock arbor chuck. The centers now will take the lathe centers without play or chatter.

If a combination drill is not available, you can drill centers with a small drill and countersink them with a drill of sufficient diameter ground to a 60° point. A 60° taper is standard for lathe center points. Correct center depth is given in Figure 11.6. Take care to get an accur

ate 60° countersink in the center (Figur

e 11.7).

Too Shallow

Correct Path

Too Deep

Figure 11.6 The correct depth of center is illustrated above. If it's too deep (bottom)

only sharp outer edges will contact the center.

Center

Work

Hole

Work

Lathe

Center

Point

Figure 11.7 Counterbore centers with a drill to a 60° point so they fit the lathe centers (A).

Too obtuse (B) or too acute (C) a counterbore will give insufficient bearing

and destroy the lathe centers.

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11-3

Midas 1220 XL Operator’s Manual

Mounting Work Between Centers

Remove the chuck from the lathe, bolt the faceplate to the spindle if l angle (Figure 11.8), and put in both headstock and tailstock centers. Fasten a lathe dog (Figure 11.9) to one end of the work. For ease of operation, use a live or rotating center in the tailstock end so you won't need lubrication.

Before centers starting the lathe, make sure the centers don't hold the workpiece too tightly. Heat may cause the workpiece to expand, so watch for binding. Adjust the tailstock center so the work turns freely but without end play.

If, after partially machining the workpiece, you find you must machine the stock under the lathe dog, remove the workpiece from the lathe and place the lathe dog on the machined end. Then turn this new tailstock center end of the shaft down to the desired diameter or form.

Figure 11.8 Bolt the faceplate to the spindle flange

Using a Clamp Dog

Standard lathe dogs drive round, or near-round, shapes. Rectangular or near-rectangular stock requires clamp dogs. In a properly made clamp dog, the under face of the heads of tightening scr bar are elongated. This design allows a firm grip of off-square shapes without bending the screws. Top and bottom bars should also have V-notches to give a firm grip on triangular or other odd-shaped stock. Y to hold highly polished round bars. Using faceplates

For work setup, faceplates serve two purposes. First, they drive workpieces held between centers. Second, they hold workpieces shaped so you can't chuck them or mount them on centers.

Faceplates for driving workpieces on centers are generally small. They're notched and

ted to receive the tail of the lathe or clamp dog, bolt drive, or other driving tool

slot (Figure10.9). Faceplates for holding workpieces (irregularly shaped casting, machine, or die parts, f T-slotted, drilled all over, or slotted and drilled. Workpieces mount on such faceplates with T-slot or standard bolts, strap clamps, angle plates, or other standard setup tools.

ews are convex and fit into concave seats, while the holes in the upper

w dogs also

-ja

or example) ar

e usual

ou can use clamp dogs or special V

aried designs. They ma

e v

ly lar

ger and ha

y be

11-4

For Assistance: Call Toll Free 1-800-476-4849

Setting Up with Centers, Collets, and Chucks

Figure 11.9 Fasten a lathe dog to one end of the work piece.

Note:

Before starting to machine work set up on centers, check to see the lathe dog tail

is free in the faceplate slot so it won't lift stock off its true line of centers, as in Figure

11.10. Also, be sure lathe centers fit closely into the center holes to eliminate side play but not so tightly they bind. If you're working on a long workpiece, check it frequently to be sure the center does not bind. Also, balance unbalanced setups with counterweights to overcome any "throw" as the work revolves (Figure 11.11).

Tail of Lathe Dog

Figure11.10 Make sure the lathe dog tail is free in the faceplate slot so

it won't lift off the true line of centers.

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Figure 11.11 Counterweights can

help with unbalanced setups.

11-5

Midas 1220 XL Operator’s Manual

Setting Up Work on a Mandrel

You can machine cylindrical or bored pipe work or cored castings too long to fit in a chuck by mounting them first on a mandrel (Figure 11.12). Then mount them between centers. The solid mandrels, which are driven into the hole of the work-piece, must be tight enough to turn the workpiece against the tool without slippage. Oil them lightly before driving them into the workpiece. Otherwise, the workpiece may freeze to the mandrel, making it impossible to remove the mandrel without damaging both workpiece and mandrel. When removing a mandrel, drive it back out of, instead of through, the hole.

You can purchase hardened steel mandrels, which have a slight (0.003") ground taper and an expanding collar, to facilitate mounting and demounting (Figure 11.13). Mandrels with compressible ends for holding single or ganged pieces are also available. When a workpiece is mounted on a mandrel, machine it as you would a solid shaft. You can drill eccentric centers in mandrel ends to permit eccentric turning.

Figure 11.12 Mount workpieces too long for of the lathe centers.

Figure 11.13 Hardened steel mandrels have a slight ground taper and expanding collar.

Steady Rests and Follow Rests

Rests are for setting up (1) work that is relatively long in proportion to its diameter or (2)

or boring or other oper

ee f

work whose dead end must be left f rests to machine slender shafts that are apt to spring out of alignment from the thrust of the tool. The purpose of a rest is to support the workpiece and maintain it in accurate alignment for machining. Rests are classed as steady rests or follow rests.

ations. Y

ou can also use

11-6

For Assistance: Call Toll Free 1-800-476-4849

Setting Up with Centers, Collets, and Chucks

Steady Rests

- Steady rests mount on the lathe bed (Figure 11.14). Clamped over the ways, they provide three bearing surfaces. These surfaces bear down lightly but rigidly against the surface of the shaft and keep it from moving out of the line without interfering with the operation.

To set up a steady rest, first center the work in the chuck and true it up. Then slip the steady rest into position and tighten it to the bed. With the bearing jaws clearing the work, close the top of the rest and tighten the locking screw. Now, with the lathe running, adjust the three bearing jaws to touch, but not push, the workpiece. Finally, test again for alignment, making sure the axis of the workpiece coincides with the axis of the lathe. Otherwise, the end will not be square and the surfaces and boring will be untrue. The tips of the jaws are bronze and require lubrication.

Figure 11.14 Steady rests mount on the lathe bed and provide three bearing surfaces

Follow Rests -

taper and al

Long or slender shafts that are apt to spring out of have a slight ground

e a follow rest

ignment by the thrust of the cutting tool often r

equir expanding collar (Figure 11.15). Follow rests mount on the carriage of the lathe and move with the tool, backing up the workpiece opposite the point of the tool thrust. They have two adjustable supporting ja

ws, one holding the work to keep i

t from cl

imbing up on the

tool and the other behind the work to counter the thrust of the tool.

Note:

Take great care in adjusting the jaws of rests, as they must form a true axial

bearing for the work and let it turn freely but without play.

Figure 11.15 Follow rests mount on the lathe carriage and move with the tool.

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Midas 1220 XL Operator’s Manual

Setting Up Work in a Chuck

Chucks usually hold work that is too short to hold conveniently between centers or work requiring machining at, into (boring or inside threading), or across its end. While it is possible to set up such work on a faceplate, the convenience of chucks has made them part of every complete lathe. Lathe chucks come in many types and sizes and hold workpieces of diameters approaching the swing of the lathe.

For ordinary use, there are two standard types of headstock chucks. The four-jaw independent lathe chuck has four holding jaws that can operate independently and adjust to hold round, square, eccentric, or odd-shaped work (Figure 11.16). The three-jaw universal geared scroll chuck holds only round or near-round work with three, six, nine, 12, or other multiple-numbered sides. It always holds work concentrically. The three-jaw chuck has the advantage of being self-centering-all jaws move in or out together (Figure

11.17).

Figure 11.16 Four-jaw independent lathe chucks hold round, square, eccentric

or odd shaped workpieces.

Figure 11.17 Three-jaw universal geared scroll chucks hold round or near-round workpices.

Mounting Work in a Four-Jaw Independent Lathe Chuck

For small-diameter, short work, insert jaws in the chuck with high ends to the center. This gives the maximum gripping and tool clearance (Figure 10.18). For large-diameter work, insert the ja chuck (Figure 11.19).

ws in the chuck slots wi

th the high steps of the jaws to the outside of the

11-8

For Assistance: Call Toll Free 1-800-476-4849

Setting Up with Centers, Collets, and Chucks

To place work in a chuck, follow these steps:

1. Adjust the chuck jaws to the approximate opening to receive the work. Roughly center them by matching the nearest concentric ring on the chuck face with the corresponding mark on the jaws.

2. Place the work in the chuck and grip it. Turn up the opposing jaws a uniform number of turns with the key provided. This will hold the work in position. Then bring in the other pair of opposing jaws the same way.

3. Revolve the spindle slowly with your left hand while holding a piece of chalk until the chalk touches the high point (the nearest surface) of the work (Figure 11.6).

4. Guided by the chalk marks, readjust the jaws until a chalk line lathe chucks hold round, will carry completely around the work. Then tighten all the jaws securely. square, eccentric, or odd-shaped workpieces.

For greater accuracy, after roughly centering the stock using chalk, set a dial indicator at the back of, and square to, the stock. Make sure you can see it clearly. Rotate the chuck by hand. Looking at two opposing jaws, determine which side is higher

. Align the higher side with the dial indicator, loosen the opposite jaw, and tighten the higher jaw. Do the same with the other two jaws. Repeat the process until you have located the stock

thin necessary tolerances.

When making several identical pieces, after completing each workpiece release only two adjoining jaws, leaving the others to hold the center

. The jaws of the four-jaw independent chuck are reversible. You can insert them with high steps to the inside or outside.

Figure 11.18 For short, small-diameter workpieces, insert

the jaws with high ends to the center.

Figure 11.19 For large-diameter workpieces insert the

jaws with high steps of the jaws to the outside.

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Midas 1220 XL Operator’s Manual

Caution

ever leave the chuck key (wrench) in the chuck while the chuck is on the spindle. Any movement of the spindle can crash the key into the ways, seriously damaging the ways, spindle, and chuck. Turning on the lathe with the key in the chuck can seriously damage your lathe. The key can also be thrown when the lathe starts, causing damage and/or injury. Never let your hand leave the chuck key unless you are picking it up or storing it.

Never remove a chuck or heavy faceplate without first laying a board across the ways to protect them in case the chuck falls when it comes off the spindle nose. Or use a chuck cradle to ease chuck removal and installation.

Mounting Work in a Three-Jaw Universal Chuck

Work is set up in a three-jaw universal chuck as in a four-jaw independent chuck, with these exceptions:

• On three-jaw chucks, the key moves all the jaws at once.

• You need not center or check f automatically.

• Jaws are not r high steps toward the inside (inside jaws), the other for mounting in the chuck with high steps to the outside (outside jaws).

• When installing the chuck jaws on a three-jaw chuck, install them in numerical order and counter

Each jaw is stamped with a serial number and jaw number (#1, #2, or #3). The slots in the chuck ar

11.20). With the #1 slot in the 12:00 position, the #2 slot is at 8:00 and the #3 slot at 4:00 (Figure 11.21).

To install the jaws, first insert the #1 jaw into the #1 slot and turn the key until it engages. Then put in the #2 jaw and engage it, then the #3 jaw.

eversible. Each chuck comes with two sets of jaws. One is for setups with

clockwise rotation.

e not numbered, but there is a serial number stamped at the #1 slot (Figure

or concentricity because these chucks center

Figure11.20 A serial number is stamped in the #1 slot of the three-jaw chuck.

11-10

For Assistance: Call Toll Free 1-800-476-4849

Setting Up with Centers, Collets, and Chucks

Slot #3

lot #2

Slot #1

Figure11.21 With the slot for the #1 jaw in the 12:00 position, the slot for the #2 jaw is at 8:00

and the slot for the #3 jaw is at 4:00.

Collets and Collet Attachments

To hold small-diameter work, whether bar stock fed through the hole in the spindle or small pieces of semi finished parts, collet attachments are preferable to standard chucks (Figure 11.22) for several reasons:

• They have much faster release and grip actions.

• They center the work automatical

ly and ac

curately

• They grip even small pieces and pieces with a short hold firmly.

Figure 11.22 Collet attachments are best for small-diameter work.

• They are housed within the spindle nose for maximum tool clearance, making it possible to machine, thread, or cut off close to the spindle.

While chucks are universal tools that hold a range of stock sizes and shapes, collets are special tools. Ther

e is a col

let f

or ev

ery siz

e and shape of workpiece.

Made with extreme accuracy, hardened, and ground, standard split collets are slotted so their jaw ends compress inwardly to grip the workpiece. This is done by pulling the collet jaw's externally tapered shoulder into a matching taper-bored adapter sleeve. The adapter sleeve connects the lathe spindles MT5 taper to the collets MT3 taper. A drawbar holds the col

let in place.

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Midas 1220 XL Operator’s Manual

Toolpost Grinders

A fully equipped lathe has a toolpost grinder, a small, independently operated grinding head with an integral electric motor that mounts as a unit in the toolpost T-slot of the compound rest. (For lighter work, some are held in the toolpost.) You can maneuver it as you would any other cutting tool.

Toolpost grinders come with wheels of different shapes, sizes, and grits for grinding different materials and surfaces. They also come with arbors and mounted wheels for grinding internal surfaces. You can use them to grind or polish surfaces; to grind lathe centers, arbors, taper sockets, leader pins, gauges, valve seats, and other close-fitting parts; and to sharpen tools.

11-12

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Chapter 12

Lathe Turning

Rough Turning

1. In turning a shaft to size and shape where you have to cut away a lot of stock, take

heavy, rough cuts to get the work done in the least time. Use a transverse powerfeed for heavy cuts-from right to left toward the headstock so the thrust is against the headstock or the chuck. Use a right-hand turning or round nose cutter.

2. After selecting a cutter, place it into the left side of the turret (Figure 12.1). The cutter’s point should be just above or on the line of the centers. The greater the diameter of the work, the higher the cutter can be. Adjust the height by placing shims under the cutter and raising or lowering it (Figure10.1).

Figure 12.1 Place a cutter into the left side of the turret.

3. With the tool properly positioned, tighten the Allen capscrew.

4. Next, run the carriage to the right end of the workpiece with the crank. Make sure the

lathe is set to feed toward the headstock.

5. Now determine the depth of the cut. Move the tool to the desired depth till it just touches the stock and zero the cross-feed dial.

6. Start the lathe. Run the crossfeed in by hand to take as heavy a cut as is consistent with the power of the drive or the amount of metal to remove.

Say, for example, you need to reduce a diameter by a known number of thousandths of an inch. If y of the feed from the zeroing point.

Note:

measuring instrument.

ou zero the collar and watch the movement of the dial, you’ll know the depth

The dial giv

es a good appr

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ements, use a

12-1

Midas 1220 XL Operator’s Manual

To reduce the diameter, advance the tool only half as many thousandths on the dial. This is because the tool takes off an equal amount from both sides as it cuts a continuous strip around the work. For example, to reduce the diameter of a shaft 0.005”, you advance the tool only 0.0025”, or 1-1/4 calibrations.

Engage the tool before setting the floating dial. The tool must be moving in the direction you want to go before you set the dial to zero to compensate for the backlash.

For a screw to move, there must be some play in the thread. When backing the cutting tool away from the cut, move the feedscrew enough to take the backlash before setting the collar or when the drawing the tool from the cut. Normal backlash is 0.008 – 0.015”.

Engage the longitudinal feed by rotating the half nut lever 90 degree to the right. Always cut deeply enough to reach below the scale on oxidized bars or iron castings. Hard, oxidized surfaces dull tools rapidly.

Finish Turning

1. After you have rough-turned the workpiece to approximate finished size (within 1/32”),

replace your cutter bit with a freshly ground, keen-edge cutter.

2. Make one or more light finishing cuts across the machined surface.

3. Check the diameters carefully with a calliper or micrometer to be sure you are

working to proper dimensions. Remember: the diameter will reduce twice the thickness of the cut.

For rough turning, most machinists prefer a deep cut and a comparatively fine feed, but the reverse is true for finishing cuts. They usually use a very light crossfeed and a coarse transverse feed with a cutting edge wider than the feed per revolution. In figure 12.2, the left-hand tool illustrates the first roughing cut and the right-hand tool shows the following finishing cut.

Figure 12.2 Roughing (left) and

finishing (right) cuts.

Turning to Shapes

Other turning cuts, machining shapes, corners, fillets, etc., are done the same way. The main difference is in selecting cutter bits and maneuvering the cutting point by means of various cutting tools (Figure 12.3).

12-2

For Assistance: Call Toll Free 1-800-476-4849

Lathe Turning

Left Hand

Turning

Left Hand

Facing

Left Hand

Corner

ight Hand

Turning

Turning with a roundnose cutter

Finishing Cut

Parting or cutting off

Special-form cutter

Right Hand

Facing

Figure 12.3 You can do other turning cuts with different cutter bits and cutting tools.

Right Hand

Corner

Machining Square Corners

To machine an accurate corner, follow these steps:

et the compound rest perpendicular to the line of the center and insert a right or

1. S left-hand corner tool.

2. Using the longitudinal feed, turn a small diameter to finish up to the shoulder.

eed the tool the amount needed to finish the work to the

th the compound r

3. Wi length, taking to the last f

Finishing and Polishing

After machining, you’ll want a smooth, polished surface free of machine marks. You’ll obtain the best r

esul

With a file, take full, biting strokes across the revolving workpiece at a slightly oblique angle. Do not drag the file back across the workpiece; instead, lift it clear for each return stroke. Use a clean, dry file and keep the workpiece clean, as well. Wipe the workpiece

ou’v

dry and clean i

f y

workpiece is revolving (Figure12.4).

est, f

acing cut acr

th a toolpost grinder. If you don’t have one, use a file.

ts wi

e used coolant or cut

oss the shoulder away from the center.

ting oil. Never hold the file stationary while the

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Midas 1220 XL Operator’s Manual

Figure 12.4 With a file, take full strokes at an oblique angle and never hold the file still.

For an even finer file finish, rub railroad chalk into its teeth. This provides additional lubrication and absorbs filings. Do not use blackboard chalk.

After filing off the machining marks, polish the workpiece with emery or other abrasive cloth. Keep the lathe turning at high speed and spread a few drops of oil on the workpiece. Don’t stop moving the cloth (Figure 12.5).

Figure 12.5 You can polish a workpiece with an abrasive cloth and oil.

Taper Turning

There are two ways to turn a taper: with the compound rest and by setting over the tailstock. In both methods, the cutter must engage the work on dead center if the taper

ate.

is to be ac

Compound Rest.

such as centers, bevel gear blanks, and die parts (Figure 12.6). In general, these are not considered taper turning, which applies to machining longer, more gradual tapers.

Setting over the tailstock.

misaligning the lathe centers. The lathe centers move from their position parallel to the tool’s transverse travel, giving the desired degree of taper (Figure12.7) The tailstock has a set-over scale calibrated both forward and backward from the straight turning or zeroing point for measuring set-over distances.

12-4

cur

Tapers cut with the compound rest are usually short, abrupt angles,

ting tapers b

Cut

For Assistance: Call Toll Free 1-800-476-4849

y setting over the lathe tailstock involves

Figure 12.6 Tapers cut with the compound rest are

usually short, abrupt angles.

Lathe Turning

Figure 12.7 In setting over the tailstock, the lathe centers move

from their parallel position with the tool’s transverse travel.

To offset the tailstock, adjust the two base-locking bolts (Figure5.8). To offset to the right, loosen the right adjusting bolt and tighten the left. To offset to the left, loosen the left adjusting bol

t and tighten the right.

You can turn long, gradual tapers by setting over the tailstock, but take care. Your computations must be nearly perfect, because an error will spoil your work.

The distance of tailstock set-over needed to machine any given taper depends on three

actors:

• The differential between the finished diameters of the extreme ends of the taper

• The length of the taper in relation to its extreme diameters, if the entire shaft is to be tapered

• The ratio between the length of the shaft (or work between centers when you’re tapering only part of the shaft).

When the taper extends the entire length of the workpiece, tailstock set-over should equal hal

f the difference between the finished diameters of the ends (Figure 12.8). When

a taper extends only part of the length of the shaft, divide the total shaft length by the length of the portion to be tapered. Then multiply the resulting quotient by half the

ence between the extr

dif

eme diameters of the finished taper

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Midas 1220 XL Operator’s Manual

Figure 12.8 Tailstock set over should be half the difference between the finished diameters of

the ends. That is 0=T” x L”/2 where T= taper per inch and L=length of work in inches.

Note:

(A) Because most drawings give the taper in inches per foot of length, it may be easier to convert all dimensions to inches. (B) Be sure to zero the tailstock before resuming straight turning.

Boring a Tapered Hole

Boring a tapered hole involves setting the compound at the desired degree of taper and feeding the tool with the compound rest. Make sure the compound rest is set at half the degrees of the angle of the completed taper hole. You can also use a taper at to bore a tapered hole.

tachment

12-6

For Assistance: Call Toll Free 1-800-476-4849

Chapter 13

Lathe Facing and Knurling

Before removing your work from the centers, face or square up the ends. On accurate work, especially where shoulders, bevels, and the like must be an accurate distance from the ends, do the facing before turning the shank. This also cleans the ends and machines the workpiece to accurate length.

When diameters are large, it's best to face with a special side tool that has a long, thin blade with a wide cutting edge. If you don't have one, use a right or left-hand facing cutter. Feed the tool from the center outward to avoid marring the lathe center (Figure

13.1).

Figure 13.1 With a facing cutter, feed the tool from the center outward.

Facing Across the Chuck

When facing a stub-end workpiece held in the headstock chuck, the same rules apply.

otrude about an inch. Place a right-hand side tool (or a

t pr

Chuck the stock, let straight turning tool with a facing cutter) in the toolpost. Carefully adjust the cutting edge so it is exactly on center, then tighten it into the toolpost. If you don't do this, a small tit

ojection wi

or pr run off center.

Start your lathe on the slowest speed. Bring the tool into cutting position against the center of the workpiece. Do not start with a heavy feed because the sfm increases rapidly as the cutter moves through increasing peripheries. One or two light cuts is

ly enough to true up an end r

usual reverse the workpiece and face the opposite end.

If you must finish the ends of the shaft, use a half-center (Figure 13.2). This lets you extend the tool across the entire face of the work.

To use the powerf

ting i

emain in the center of the stock and perhaps cause the center dri

l r

. After facing one end,

oughened b

eed for facing, place the speed selector into the desired position before

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Midas 1220 XL Operator’s Manual

the lathe is turned on. Once the cutter has been positioned as per the above paragraph, move the crossfeed lever down. Pull the lever up at the end of the cut to stop the cutter travel.

Caution

Remember caution must be taken to not run the powerfeed past their limits of travel. As part of the normal operation, procedures, run each axis through the entire length of the proposed machining operation before engaging the powerfeed to assure there is sufficient travel to accomplish for the desired task. Failure to so could result in running the power feed to the end of its mechanical limit. This is what is known as a "CRASH". A crash can cause damage to the work piece and severe damage to the machine.

Figure 13.2 With a half-center you can extend the tool across the entire face of the work.

Knurling

Strictly speaking, knurling is not a machining operation because no metal is cut. It is a

orming oper

f raising the surface of the metal into a pattern. As with all other forming operations, your work can be no better than the pattern, your knurling no better than the knurls. Be sure the knurls are sharp, clean-cut (preferably hob-cut), and properly hardened.

To make a true, uniform knurl, maintain uniform pressure on both knurls. Select a

-centering knurl

sel

ong enough to withstand end and side thrusts. Operate the lathe at the slowest speed

str (160 rpm).

Knurling exerts extreme thrust against centers and bearings. You can lessen this thrust material of the workpiece. This engages the right side of the knurl first (Figur

Place a few drops of oil on the workpiece and knurling tool. Start the rolls of the knurling tool from the right-hand scribe line and feed them in until the knurl reaches a depth of 1/64". Then stop the lathe and inspect the work. If the knurl is not clear-cut, adjust the tool in or out as needed.

ation in which patterned knurls are pressed into the work, depressing and

ing tool that equalizes pressure on the knurls automatically and is

eeding the knurling tool at a slight angle off from perpendicular to the line

y f

ly b

e 13.3).

13-2

For Assistance: Call Toll Free 1-800-476-4849

Lathe Facing and Knurling

Use plenty of oil, lubricating both knurl and workpiece. Then start the lathe and engage the automatic feed, moving the knurls across the portion to be knurled. When you reach the left scribe line, force the tool into the work another 1/64", reverse the lathe without removing the tool, and feed it back to the starting point. Feed both ways using the automatic longitudinal feed. Once across, each way, usually makes a good knurl.

Figure 13.3 Feed the knurling tool at a slight angle off from perpendicular to the

line of the work piece.

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13-3

Chapter 14

Changing Gears

To change the gears on the MI-1220 XL, follow these steps. You will need a 10mm wrench, 6mm Allen wrench, screwdriver (to remove C clips), and pliers (to replace C clips).

1. Remove all C clips, nuts, and gears, starting with the A gear and ending with the D gear. With the 10mm wrench, loosen the B & C gearshaft in its bracket by turning the gearshaft counterclockwise (Figure 14.1). This lets the shaft slide freely along the bracket for easy gear removal and replacement.

Figure 14.1 Remove all C clips, nuts and gears.

2. Select the pr

3. Use the Allen wrench to loosen the bolt at the bottom of the bracket assembly for full

swing and easy gear r

4. Place the selected D gear on the D shaft, flange side in. R and nut.

5. Place the selected C gear

6. Place the selected B gear, flange side in, on the B & C gearshaft. Replace the C clip.

7. Slide the B & C gearshaft unitl the C gear meshes properly with the D gear and

tighten it with the 10mm wrench (Figure 14.2).

oper A-D gear combination from the list outside the pulley box door.

.1).

eplacement (Figur

, flange side in, on the B

e 14

eplace the spacer, washer

gearshaft.

14-1

For Assistance: Call Toll Free 1-800-476-4849

Figure 14.2 Slide the B and C gearshaft until the C geal meshes with the D gear.

8. Place the selected A gear, flange side in on the A gearshaft and replace the C clip.

Changing Gears

9. Swing the bracket assembly until the A and B gears mesh. Hold the bracket assembly in place and tighten the bol

t. Mak

e sure the gears turn smoothly before engaging the

powerfeed. You may need to make some adjustments.

10. Engage the E gear between the C and D gears to reverse the leadscrew (Figure 14.3).

Figure 14.3 Engage the E gear between the C and D gears to reverse the leadscrew.

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14-2

Chapter 15

Cutting Screw Threads

Threading Terms

Before beginning to cut threads, it’s useful to learn the major terms used in thread cutting:

Pitch.

thread. To measure pitch in inches, measure an inch on a bolt and count the threads.

Pitch Diameter.

straight screw thread, the surface of which would make an equal width of the thread and the spaces cut by the cylinder.

Lead.

one complete revolution. The lead and pitch of a single thread are identical, but they differ on multiple threads (the lead of a double thread is twice its pitch; of a triple thread, three times its pitch).

Because thr building things of metal should master it. Threading requires a bit of patience and skill. Before trying to cut a thread on a workpiece, cut a few practice threads on odds bits of steel, ir

Built for thread cutting, The Midas 1220 XL cuts standard internal and external threads, as wel per inch, in V or square shapes, in established profiles like Unified National, acme and metric. Y shaft. You determine the type of thread by how you’ll use the screw. Each thread form requires a different-shaped tool to cut or chase it.

Metric pitch is the distance from the center of a thread to the center of the next

This is the diameter of an imaginary cylinder superimposed on a

The lead is the distance a screw thread advances axially (as through a nut) with

ead cut

on and aluminium.

l as special threads. Y

ou can cut single thr

ting is so much a part of a machine work, anyone inter

ou may cut coarse or fine threads in a great range of threads

eads or mul

tiple thr

eads that run concurr

ently along the

ested in

Beginners will use the Unified National Standards most of the time, which is V-form thread

ly flat on top and at the r

ight

sl numbers, such as 18 or 24, meaning 18 or 24 threads per inch (tpi). The Midas 1220 XL cuts standard threads in pitches from 6 to 30 tpi and metric threads from 0.50 to 3mm.

Because the lathe spindle turning the work connects by gearing to the leadscrew (which moves the cutting tool along the lathe bed), a ratio exists between spindle speed in

olutions pr

r gearing, y changing both the change gears at the head of the lathe and the speed selection lever.

Thread charts inside the gearbox door show both inch and metric measures (Figure 7.2). The inch chart on the headstock shows the tpi f distance fr

e minute and cut

ou change this r

om thr

ead cr

est 0.12 to 3 mm.

atio

15-1

ew thr

oot. S

ting tool mo

. For this reason you can cut threads of various pitches by

For Assistance: Call Toll Free 1-800-476-4849

eads ar

ement in inches. When you change the

e usually referred to by pitch

om 6 to 30. The metric show the

Cutting Screw Threads

For right-hand threads, start the threading tool at the right end of the workpiece and feed it toward the headstock. For lef-hand threads, reverse the leadscrew’s rotation direction and feed the threading tool from left to right.

With practice, you can grind cutters to almost any profile. It is difficult, however, to sharpen such cutters without altering the cutting form, and almost every re-sharpening requires a complete regrinding of profile and clearance angles.

After turning the work to be threaded to the outside diameter of the thread and setting the gears for the desired thread, put a threading tool in the toolpost. Set it exactly on the dead center of the workpiece you’ll be threading, using a center gauge as a guide.

To make sure your cutter is on dead center, place a credit card or shim between the cutter point and workpiece (Figure 15.1). When the tool is on dead center, the card or shim will remain vertical. With a credit card, there is no possibility of chipping the cutter as the workpiece and cutter come together.

Figure 15.1 Check dead center with a

credit card.

Set the compound perpendicular to the line of centers and r

otate i

t 29-1/2 degree to the right (Figure 15.2). Place the thread gauge on the point of the threading tool and feed the tool toward the workpiece (Figure 15.3). Adjust the tool so the edge of the gauge is exactly parallel to the workpiece. A slip of white paper held below the gauge will help check the parallel of the gauge to the shaft and the fit of the toolpoint in the V of the gauge. Placing the threading tool perpendicular to the surface of the workpiece assures a true-form thread.

Figure 15.2 With the compound perpendicular to the

line of centers, Rotate it 29 degree to the right.

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Midas 1220 XL Operator’s Manual

Workpiece

Center Gauge

Toolbit

15.3 Using a center gauge, set the threading tool at exactly dead center on the workpiece.

Cutting Right Hand Threads

Now you are ready to cut right-hand threads, First, advance the tool so it just touches the workpiece and turn the compound calibration back to zero. Then, using the compound feed, feed in the tool 0.002”. Next, turn on the lathe and engage the half-nut lever by carefully turning it one-quarter turn to the right. Do not force it, and do no disengage I until you are completely done.

It is best to take a light, scratch cut first without using cutting fluid. After the tool runs the desired length, turn off the lathe and back the tool out of the work. Then reverse the motor to return the tool to the starting position. Using a screw-pitch gauge, check the thread pitch. The benefit of taking the light cuts is that you can correct any mistakes you might have made.

It’s time to take the real cut now, so apply the appropriate cutting fluid to the workpiece. Feed the cross slide in 0.005-0.020” for the first run, depending on the pitch of the thread you have to cut. If you are cutting a coarse thread, start by taking a few heavy cuts. Reduce the cut depth for each run until it is about 0.002” at the final run. Zero the cross-feed calibration and make the second cut.

Continue this process until the tool is within 0.010” of the finished depth. Brush the

e chips. After the second cut, check the thread fit using a ring

egularly to r

eads r

thr gauge, a standar

emo

d nut or mating part, or a scr

-thread micrometer. It is best to leave

the workpiece in the chuck and not to remove it for testing.

After returning the workpiece to the setup, continue taking 0.00-0.002” cuts, checking the fit between cuts. When you thread the nut, it should go on easily but without end play.

e the desired fit, chamfer the end of the thread (that is, take 45 degree cut

When y of

ou ha

f the end) to pr

otect it from damage, Figure 15.4.

15-3

For Assistance: Call Toll Free 1-800-476-4849

Cutting Screw Threads

efore

15.4 Chamfer the end of the thread to protect it from damage.

ool

After

Cutting Left Hand Threads

Cut left-hand threads exactly as you cut right-hand threads, except this time feed the carriage toward the tailstock instead of away from it. Reverse the cutter clearances and grind the cutters back with a clearance angle on the left side. Swing the compound rest to the left rather than to the right.

Cutting Multiple Threads

Cut multiple threads (Figure 15.5) one at a time exactly as you cut single threads, except increase the lead to make room for succeeding threads ( a double lead for a double

ead, a triple lead for a triple thread, etc.). After completing the first thread, remove

thr the work f

rom the centers wi with the tail of the lathe dog in the correct slot to index the work for the next thread. This work r

equires a f

aceplate with accurately position slots, uniformly spaced and equal in

number to the number of threads to be cut.

Single Thread

thout loosening the lathe dog. Then put it back in the lathe

Double Thread

Triple Thread

Figure 15.5 When cutting multiple threads, increase the lead to make

room for succeeding threads.

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What Not To Do When Cutting Threads

Do not disengage the half-nut lever. Do not shift the powerfeed speed lever. If you are cutting between centers don’t remove the lathe dog until the tread is finished and tested, and don’t disturb the spindle while the work is off the centers.

When you think the thread is finished and ready for testing, and only if absolutely necessary, remove the work from the center, leaving the lathe dog attached. Then test the thread. If it does not fit properly and you have to remove another chip or two, place the workpiece back in the centers exactly where it had been. Then remove the hips and test again. Repeat until are finished.

Finishing Off a Threaded End

After cutting a thread and before removing the threading tool, chamfer the end. This improves its appearance and removes sharp corners and burrs. It also aids the screws as

t engages a nut or threaded hole.

Cutting Threads on a Taper

Cut threads on a taper the same as on a straight shaft, except in the setup of the tool. Set the threading tool at 90 degree to the axis of the taper, rather at 90 degree to its surface (Figure 15.6)

Figure 15.6 When cutting a thread on a taper,

set the threading tool at 90 degree to the axis of the taper.

15-5

For Assistance: Call Toll Free 1-800-476-4849

Chapter 16

Lathe Drilling and Boring

You can lathe drill on the MI-1220 XL in two ways, holding the drill stationary and revolving the workpiece, or holding the workpiece stationary and revolving the drill. Holding the drill stationary in a tailstock chuck gives a straighter hole (Figure 16.1).

Without changing setup and re-centering, the work is ready for any succeeding operations, such as boring and internal threading. In all lathe drilling operations, keep the drill sharp and properly ground. This is essential for obtaining a straight, accurate hole.

Figure 16.1 Holding the drill stationary in the tailstock chuck gives a straighter hole.

With HSS drills, operating speeds are not as critical as with carbon-steel drills High speeds can quickly "burn" a carbon-steel dri drills even more than to other cutting edges because there is practically no air cooling of the point after i peripher no drilling speed data are available, it's generally safe to run drills under 1/4" diameter at up to 750 rpm and drills up to 1/2" diameter at 500 rpm, with larger drills at proportionately slower speeds.

With the workpiece in the headstock and the drill in the tailstock chuck, feed the drill into the workpiece b Make a locating center for the drill point, or even a countersunk center for large diameters, to k

al f

t enters the hole. The larger the dri

eet cut per revolution. That is why you should use a slower drilling speed. If

y advancing the tailstock ram. Do this by turning the tailstock handwheel.

om cr

l f

eep the dri

ll. The number

eeping.

-of-feet-per-minute rule applies to

ll, the greater the number of

Reaming

ightly undersized (0.010" to

t sl

l i

ate to 0.002" or less, dri

When a hole must be ac 1/64" on smal it either by hand or in the lathe. Lathe reaming is usually done with solid reamers held in a tailstock chuck or with a taper shank that fits the tailstock ram in place of the tailstock center. Use slow speeds and feed the reamer slowly and evenly into the workpiece. Be sure the reamer teeth are free of burrs and chips.

l diameters and 1/64" to 1/32" on holes 1" to 2" in diameter). Then r

cur

eam

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Midas 1220 XL Operator’s Manual

Boring

Boring is internal turning, or turning from within. The diameter of the opening to be bored is often much smaller than its depth. Boring tools must therefore have relatively small diameters and still support a cutting edge projected at considerable distance from the toolpost or compound rest.

Boring tools consist of an extremely stiff, strong bar with a formed cutting end or a way to hold an HSS cutter or carbide insert. There are many sizes and types of boring bars. Choose the one that will give the stiffest possible bar at every depth and diameter and the greatest choice of cutters and cutter angles (ask a Smithy technician about the Smithy boring head combo package, #K99-125).

It is also wise to select tools with smooth-ended bars without a projecting nut or hardened edge that might mar the work (Figure 16.2). Most boring tools have only one cutting edge. There are double-end cutters, however, and they offer advantages in special instances. In grinding cutters, allow sufficient end rake to provide clearance from the internal diameter.

Figure 16.2 A tool with a smooth-ended bar won't mark the workpiece.

Except with cored castings, pipes, or tubing, begin by drilling a hole large enough to admit the end of the boring bar. Because the holes in cored castings often deflect boring bars from their true axis, you may want to chamfer or turn out a starting cut in the

th a turning tool (Figure 16.3) before introducing the

opening of the hole to be bor

ed wi

boring tool.

Figure 16.3 Chamfer a starting cut in the opening of the hole.

With the boring toolholder set up (in the toolpost or toolpost T-slot, depending on the type), select the largest-diameter boring bar whose cutter the bore will accept. Extend the bar from the holder just enough to r

16-2

each the f

For Assistance: Call Toll Free 1-800-476-4849

ull depth to be machined and still allow

Lathe Drilling and Boring

tool clearance. Except when using the adjustable boring tool (usually for very large diameter work), feed the bar into the hole, parallel to the holes axis. The cutting edge engages the work along a line in the mounted plane of the lathe centers with the bar positioned to give the cutter a top rake of approximately 14° from the radius at the cutting point (Figure 16.4). This takes into consideration the ground angle (top rake) of the cutter itself.

Figure 16.4 The cutting edge engages the work piece along a line in the

mounted plane of the lathe centers.

For straight longitudinal cuts, you can hold the cutter close up, therefore more rigidly, if it's at a 90° angle to the bar. For machining ends of a bar, however, you need a boring bar that holds the cutter at an angle or angles so the cutter extends beyond the end of the bar (Figure 16.5). For maximum visibility, position the cutting edge at the near side,

allel to the centerline.

par

The rules that apply to external turning apply to boring as well, except-as noted earlier wher

e the rak

e angles di

ffer. The rake angles are governed by cutter type and bore diameter. Feeds must be lighter to keep the tool from springing. This is especially true when enlarging out-of-round holes, when you take several small cuts rather than one heavy cut.

Figure 16.5 To machine ends of a bar, use a boring bar that angles

the cutter so it extends beyond the bar.

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Midas 1220 XL Operator’s Manual

After the last finish cut, it is common to reverse the feed and take one last, fine cut with the tool coming out of the work. This last cut, taken without movement of the cross-feed, avoids a slightly undersized hole because you compensate for any spring in the bar.

Cutting Internal Threads

Internal thread cutting is like external thread cutting, except you have the clearance restrictions and tool problems of boring. You use the same toolholders, but the cutters have thread forms and are fed at thread-cutting ratios of feed to spindle revolutions.

Another difference between boring and inside threading is the cutting angle at which the cutter approaches the workpiece. As with external thread cutting, the internal threading tool must engage the work on dead center and be held so the cutter coincides with the workpiece's center radius.

In squaring the cutter with the work, use a center gauge (Figure 16.6) or thread gauge. Internal cutters require greater end and side clearance, and cutter length is also restricted because internal thread cutters must have enough end clearance that for different thread types. the cutter lifts clear of the thread for removal (Figure 16.7). Before cutting an internal thread, bore the workpiece to the exact inside diameter.

Figure 16.6 Use a center or thread gauge to correct

cutter alignment error when squaring the cutter with

the workpiece.

Figure 16.7 There must be enough end clearance for the cutter to lift clear of

the thread.

16-4

For Assistance: Call Toll Free 1-800-476-4849

Lathe Drilling and Boring

Because the feed of successive cuts is toward, not away from, the operator, the thread-cutting set is reversed. Also, you must take lighter cuts because of the cutter's extension from the toolpost. Take an extra finishing cut without changing the setting of the compound rest.

Cutting Special Form Internal Threads

You can cut internal forms in all the thread forms used for external threads. There is only one factor that calls for special attention in cutting special-shaped internal threads: the difference of clearances between the nut and screw recommended for different thread types (Figure 16.8). If you don't have recommended clearances, it is safe to cut a nut thread (internal thread) 0.005" to 0.010" per inch larger in the screws outside diameter.

Figure 16.8 Use different clearances between nut and screw for different thread types.

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16-5

Chapter 17

Cutting Off or Parting with a Lathe

You can cut off in a lathe only when holding one end of the work rigidly, as in a chuck. It is not practical for long workpieces held between centers because the workpiece is not supported closely with a rest and the free section is long enough to sag and pinch the blade. Cutting off requires a tight lathe without excess play in the spindle, compound, carriage, or toolpost. Looseness will almost certainly cause chatter. Cutting off also requires a narrow cutting edge with ample (5-10°) side clearance, which should feed into the work slowly to prevent hogging in. Once considered a difficult, costly operation, cutting off became much simpler with development of narrow tools with special cutoff blades (Figure 17.1).

The toolpost should hold the cut-off tool as close to the workpiece as possible, with the top of the blade on dead center and exactly perpendicular to the line of centers. Extend the blade only far enough to pass through the work-piece, just beyond its center. The tool should feed to the workpiece on exact center the tool hogs in and the spindle stops rotating, turn off the motor and reverse the spindle by hand before backing the tool out with the crossfeed.

, slowly and evenly with the cross-feed. If

Figure 17.1 Specially designed tools like this one make cutting off easier.

Always set up the workpiece to cut off as close as possible to the headstock. If you must make a parting cut on a long shaft or on work between centers, don't complete the cut in the lathe. Finish the parting with a hacksaw and return it to the lathe for facing. Slow the spindle speed until you have a good feel for cutting off. Although lubricants and coolants ar work.

17-1

e not essential on small-diameter workpieces, use them amply on deep cut-off

For Assistance: Call Toll Free 1-800-476-4849

Chapter 18

Milling

In milling, one or more rotating cutters shape a workpiece held by a vise or other fixture. The cutters mount on arbors or at the end of the spindle on collets or adapters.

Machinists use mills to machine flat surfaces, both horizontal and vertical, and to make shoulders, grooves, fillets, keyways, T-slots, and dovetails. They can also make curved and irregular surfaces and machine accurate holes. Its variety of machining operations and high metal-removal rates makes the mill as important a tool as the lathe.

The millhead (Figure 5.1) rotates horizontally and moves vertically. A quill that moves in and out of the head carries the spindle.

You can mo leadscrew handwheels (Figure 5.1). The cross-slide handwheel turns the table longitudinally (at right angles to the spindle axis); the long-feed hand crank moves it transversely (parallel to the spindle axis).

To raise and lower the millhead, release the lock lever and put the handle into one of the three holes in the black adjusting collar. To raise the millhead, turn it counterclockwise; to lower it, turn it clockwise.

To rotate the millhead, release the lock lever and push the millhead to the desired position.

ve the table horizontally in two directions by turning the cross-slide and

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Chapter 19

Workholding

The most common ways to hold a workpiece during milling are to secure it directly to the table via clamps or hold it in a vise (Figure 19.1). If you're making many similar workpieces, you may make a special fixture to hold them. Whatever method you use, hold the workpiece securely so it won't shift during machining and support it adequately to avoid swing.

Figure 19.1 Setting up in a vise is one of the most common ways to secure your workpiece.

Mounting to the Table

If you need to al table's T-slots. Another way is to measure in from the edge of the table to the workpiece. Be sur the face of the spindle plate, chuck or taistock as a quick reference surface.

e the table and workpiece ar

ign the workpiece to the table, place it against stops that exactly fit the

e clean and f

ree of burrs. Another method is to use

Using a Vise

Vise sizes are designated by the width of the vise jaw in inches or millimeters. Plain and swivel vises range from 3 to 10" (76 to 254 mm). Tilting and universal vises range from 3-4" to 5" (76-102 mm to 127 mm).

tted with keys-small steel blocks that fit into the milling

The bases of man table T-slot for quick alignment of the vise. Before mounting a vise, make sure the bottom is clean and smooth. If there are any nicks or burrs, remove them with a honing stone. Set up the workpiece securely and correctly, and fasten the vise tightly to the table.

Plain vises ha faces either parallel to, or at 90° to, the longitudinal table travel. Swivel vises have a swivel base that bolts to the table. They're marked with degree graduations that let you position their jaws at any angle without moving the base. Universal vises tilt up or sideways, or swivel. They hold workpieces machined at a double or compound angle. Tilting vises are like universal vises except they do not tilt sideways.

y vises ar

e a flanged base wi

e fi

th slots that lets them bol

t to the table wi

th the ja

19-1

For Assistance: Call Toll Free 1-800-476-4849

Using special fixtures. Clamp both workpiece and fixture securely in place. Be sure they are clean. Watch them carefully during machining; a loose fixture or workpiece can be disastrous.

Dividing Heads

Also called indexing heads, dividing heads attach to the table to hold workpieces between centers for machining surfaces, grooves, or gear teeth at precise distances apart.

The main parts of a dividing head are its head and tailstock. The tailstock holds the outer end of the workpiece. The head is more complex. When you turn its handle, a spindle rotates through a precisely machined gearing system. A chuck can attach to the spindle face, which is set at 90° to the handle (Figure 19.2). An indexing plate is set in from the handle. By counting how many turns of the handle it takes to turn the workpiece a certain number of degrees, you can make cuts at different angles. This is how to cut gears.

Workholding

Figure 19.2 A chuck attaches to the spindle face of a dividing head.

Rotary Tables

A rotary table (Figure 19.3) is a precision worm and wheel unit that lets you cut gears, precision holes, and curved slots. Rotary tables mount vertically or horizontally to the table. T

-slots secur

fractions.

The index plate in the rotary table has several circles of equally spaced holes into which the index crankpin fits. Although the hole circles are spaced equally, the number of holes varies in different circles, so you can get many different numbers of circumference divisions. Y a Smi

ou can buy sets of index plates f

thy technician for more information.

e the work piece. A typical rotary table is graduated in degrees and

en more circumference divisions. Contact

or ev

Figure 19.3 Rotary tables let you cut gears, precision holes, and curved slots.

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19-2

Chapter 20

Holding Milling Cutters

There are several ways to hold milling cutters: in arbors, with collets and special holders, and in adapters.

Arbors

Arbors come in different sizes and lengths, with one end tapered to fit the bore in the end of the machine spindle. The Midas 1220 XL arbour, which has an MT3 taper, is driven by spindle. The arbor stays in place by means of a drawbar screwed into the end of the arbor from the top of the spindle. (Figure 20.1)

Figure 20.1 The arbor stays in place via a drawbar.

Take good care of your arbors. Store them in a rack or bin. If you won’t be using them for several days or longer, oil them to prevent rusting, especially in damp weather.

Collets and Holders

Straight-shank end mills fit into spring collets (Figure 20.2) or end mill holders (Figure

20.3). Their precision-ground shanks go into the mill spindle. When you tighten a spring collet, its hole reduces and the collets grips the end of the end mill shank evenly. Tighten

l secur

the end mi slip out and damage the workpiece, the cutter or you.

Figure 20.2 Spring collets, which fit into the

mill spindle, hold straight-shank end mills.

ely with the setscrew against the flat surface of the end mill, or it may

20-1

For Assistance: Call Toll Free 1-800-476-4849

Holding Milling Cutters

Figure 20.3 End mill holders also receive straight-shank end mills.

Adapters

Adapters mount various types and sizes of cutters on the spindle. Arbor adapters mount face mills on the spindle. Collet adapters mount end mills on the spindle. Taper-shank end mills mount in adapters that have holes with matching tapers. If the taper shank on the tool is smaller than the hole in the adapter, put a reducing sleeve into the adapter. Shell end mill adapters come in different sizes to accept different sized shell end mills.

To remove arbors or adapters held with a drawbar, follow these steps:

1. Loosen the locknut on the drawbar about two turns.

2. Hit the end of the dr

awbar with a dead-blow hammer

, releasing the arbor or adapter

from the spindle hole.

3. Hold the arbour or adapter so i

t won’

t fall out of the spindle when the drawbar is

removed.

4. Unscrew the drawbar and remove the arbour or adapter.

5. Your machine includes a tapered drift for removing tapers. Follow these steps:

6. Remove the drawbar.

7. Extend the mill spindle to expose the outer taper drift slot.

8. Rotate the spindle to align outer and inner taper drift slots. You will be able to see the

end of the adapter through both slots.

nsert the dri

9. I

ft in the slot.

10. Holding the adapter with one hand, use a non marring hammer (rubber, dead-blow, or brass) to drive the drift into the slot. The taper on the tool will release and the adapter drop out.

ters mounted in the spindle must fit accurately. There are two ways to make sure they

Cut do. For small cutters, Fit the shank of the arbour that carries the cutter directly into the taper hole at the end of the spindle. A drawbar holds the arbour in place. For large cutters, bolt the cutter directly to the end of the spindle.

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Chapter 21

Milling Cutters

Choose milling cutters for the type of cut, the number of parts, and the material. Rake angles depend on both cutter and work material. Clearance angles range from 3° to 6° for hard or tough materials to 6° to 12° for soft materials.

To determine the number of teeth you want, consider the following:

• There should not be so many teeth that they reduce the free flow of chips.

• The chip space should be smooth so chips don't clog.

• Don't engage more than two teeth at a time in the cut.

End Mill Cutters

End mill cutters cut on their ends and sides. They are either solid (cut from a single piece of material) or shell (separate cutter body and shank). They have two, three, four, or

e teeth and may do right or left-handed cutting. Their flute twist or helix may also be

mor right or left-handed. Solid end mills have straight or tapered shanks; shell end mill adapters have taper

ed shanks.

End mills machine horizontal, vertical, angular, or irregular surfaces in making slots, keyways, pock

•

Two flute, or center-cutting, end mills

center of the mill. They may feed into the work like a drill (called plunge milling), then go lengthwise to form a slot. Teeth may be on one end (single-ended) or both ends (double-ended).

•

Multiple flute end mills

double-ended. Mul non-center cutting end mills for plunge milling.

•

Geometry forming end mills

roughing end mills, dovetail end mills, T-slot cutters, key seat cutters, and shell end mills.

ets, shoulders, and flat surfaces.

(Figur

, six, or eight flutes and ma

our

ee, f

e thr

e center cut

ls ar

tiple-flute mi

form particular geometries. They include ball end mills,

e 21.1) have two teeth that cut to the

Figure 21.1 Two-flute end mills have two

teeth that cut the center of the mill.

y be single or

ting or non-center cutting. Don't use

21-1

For Assistance: Call Toll Free 1-800-476-4849

Milling Cutters

•

Ball end mills

(Figure 21.2) cut slots or fillets with a radius bottom, round out pockets and bottoms of holes, and do die sinking and die making. Four-fluted ball end mills with center cutting lips are available.

Figure 21.2 Ball end mills cut slots or fillets with a radius bottom.

•

Roughing end mills

remove large amounts of metal rapidly with minimum horsepower. They have three to eight flutes. Also called hogging end mills, they have wavy teeth on their periphery that pro-vide many cutting edges, minimizing chatter.

•

T-slot cutters

-slots. After machining a gr

cut T

oove for the narrow part of the T-slot

with an end or side mill, finish up with the T-slot cutter.

•

Keyseat cutters

•

Shell end mills

cut keyseats for Woodruff keys (shaped like a half circle).

(Figure 21.3) which mill wide, flat surfaces, have a hole for mounting on a short arbor. The center of the shell is recessed to provide space fro screw or nut that fastens the cutter to the arbor. The teeth ar

e usual

ly helical, and diameters are as large

as 6”.

Figure 21.3 Shell end mills mill wide, flat surfaces and mount on arbors.

• Insert-type end mills use r inserts; larger end mills, three or more.

•

Face milling cutters

Most of the cutting takes place on the periphery. They are similar to, but larger than, shell end mills.

eplaceable HS

start in siz

ls use two

S or carbide inserts. Smal

l end mi

e at 2" and have inserted teeth the periphery and face.

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Plain Milling Cutters

Plain milling cutters have teeth only on their periphery. Used to mill plain, flat surfaces, they may combine with other cutters to produce various shapes. They are cylindrical and come in many widths and diameters.

•

Light-duty plain cutters

have straight teeth parallel to the cutter axis. Wide ones have helical teeth at a 25° angle. Features include ease of starting cuts, little chatter, and good surface finishes.

•

Heavy-duty plain cutters, or coarse-tooth cutters

have larger and fewer teeth. Strongly supported cutting edges and wide flutes provide strength and space for heavy chip removal. The helix angle of their teeth is 25° to 45°.

•

Helical plain milling cutters

45-60° or greater. These cutters are for wide, shallow profiling cuts on brass or soft steel.

for light cuts and fine feeds come in two forms. Narrow ones

, come in larger widths and

have even fewer and coarser teeth with a helix angle of

Side Milling Cutters

Similar to plain mi (Figure 21.4). The teeth on the periphery do most of the cutting; those on the sides finish the side of the cut to size. They cut grooves or slots and often work with other cutters to mill special shapes in one operation.

•

Plain side milling cutters

teeth taper toward the center of the cutter, giving side relief or clearance.

lling cut

Figure 21.4 Side milling cutters are similar to plain milling cutter

ters, side mi

but they have teeth on one or both sides.

lling cutters also have teeth on one or both sides

e straight teeth on the periphery and both sides. Side

Half side milling cutters

• ters do hea

cut one side. The side teeth are deeper and longer for more chip clearance.

•

Staggered-tooth side milling cutters

opposite sides. There is less dragging and scoring and more space for chip removal. These cutters do heavy-duty operations.

vy-duty face milling and straddle milling where teeth are needed on only

21-3

ical teeth on the periphery and one side. These

e hel

are narrow cutters with teeth alternating on

For Assistance: Call Toll Free 1-800-476-4849

Milling Cutters

Slitting Saws

Slitting saws do narrow slotting and cut-off operations.

•

Plain slitting saws

are fine, and the sides taper slightly toward the hole, giving side relief.

•

Slitting saws

and cut-off operations normally done with plain slitting saws.

•

Staggered-tooth slitting saws

left-hand helix and alternate side teeth. They are for 0.2" and wider cuts and may do deeper cuts with standard feeds.

•

Screw-slotting cutters

screw heads. Their sides are straight and parallel and offer no side relief.

are thin, plain milling cutters with only peripheral teeth. The teeth

with side teeth are like side milling cutters and are for deeper slotting

have peripheral teeth with alternate right and

are plain slitting saws with fine-pitch teeth that cut slots in

Angle Milling Cutters

Angle milling cutters, f teeth, come as single and double-angle cutters.

•

Single-angle cutters

the straight side, and they usually have 45° or 60° angles.

•

Double-angle cutters

usually have an included angle of 45°, 60°, or 90°.

or such oper

have one angular surf

machine V-gr

ations as cutting V-grooves, dovetails, and reamer

ace. Teeth are on the angular surface and

ooves. Those with equal angles on both faces

Form-Relieved Cutters

Formed-tooth cutters machine surfaces with curved outlines. You can sharpen them without changing the tooth outline. Concave cutters mill convex half-circles; convex

aces.

e surf

ters cut conca

cut

•

Corner-rounding cutters

Gear cutters

•

Fluting cutters

round outside corners.

cut gear teeth.

cut flutes in r

eamers and mi

ing cut

ters.

•

Formed-tooth cutters

Flycutters

With one or more single-point toolbits or cutters, flycutters (Figure 21.5) perform end milling even though they're not end mills. They take light face cuts from large surface areas. You must grind the toolbit properly to get correct rake and clearance angles. Grind

come in right and left

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-hand styles and various special shapes.

21-4

Midas 1220 XL Operator’s Manual

toolbits for flycutters as you grind lathe tools (Section Seven).

You can also use flycutters for boring.

Note:

When the tool revolves, the cutting tool becomes almost invisible, so be careful.

Figure 21.5 Flycutters take light face cuts from large surface areas.

Using Cutting Fluid

Cutting fluids get rid of heat generated by the friction of the milling cutter against the workpiece. They also lubricate the interface between the cut and flush chips away. You can apply fluid in a stream (flood) or as a mist.

We recommend cutting fluids for steel, aluminum, and copper alloys. With cast iron and steel, however, they tend to reduce the life of carbide tools, leaving tiny cracks along the cutting edge. Follow the advice of tool manufacturers to avoid tool failure. Materials such as cast iron, brass, and plastics are often machined dry. You can use compressed air to cool tools and clear chips away. When doing so, wear a face mask and protective clothing (Figure 21.6), and be careful to keep cast-iron dust from getting between the lathe and carriage w

ays.

ting edge and the workpiece

Figure 21.6 When using compressed air, wear a face mask and protective clothing.

21-5

For Assistance: Call Toll Free 1-800-476-4849

Milling Cutters

Tool Grinding

Sharpen cutting tools when they become dull, or extreme forces may build up at the cutting edge of the teeth, causing chipping or fracture. Dull cutters are also inefficient, and regrinding very dull cutters shortens their life considerably.

The form of the cutting edge and the clearance back of the cutting edge (land) affect cutter operation significantly. The angle formed by the land and a line tangent to the cutter at the tooth tip is the primary clearance. The angle between the back of the land and the heel of the tooth is the secondary clearance. Check both clearances and the rake.

Some cutters are sharpened on the periphery by grinding the land at a suitable angle. They include cutters with straight or spiral teeth, angular cutters, side milling cutters, face mills, end mills, and reamers.

You sharpen others by grinding the front faces of their teeth. Formed or relieved cutters, for example, have profiles that must be preserved. This category includes all sorts of formed cutters as well as cutters used for milling various regular and irregular shapes.

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21-6

Chapter 22

Speeds and Feeds for Milling

Speeds

Milling cutting rates vary according to the machinability of the material being cut; whether cutting fluid is used and, if so, what kind; the type, size and material of the cutter and the coarseness of its teeth; and the amount of metal being removed. Cutting speed for milling is the distance the cutting edge of a tooth travels in one minute. If cutting speed is too high, the cutter overheats and dulls. If it’s too low, production is inefficient and rough.

There is no exact right cutting speed for milling for a particular material (Table 22.1). Machinists usually start with an average speed, then increase or decrease it as appropriate. For light cuts, use the upper end. Use the lower end for heavy cuts and when you don’t use cutting fluid.

Determining rpm. To set the spindle speed, you have to know the cutter rpm (revolutions per minute). For inch measurement, use the following formula:

Rpm = 12 x CS (fpm) / D” x pi

where CS = cutting speed, mpm = meters per minute, D (mm) diameter of the cutter

llimetres, and

in mi cutting tools at different cutting speeds.

To change speeds, set the belts ac

pi = 3.14 Y

ou can use an rpm chart f

cording to Figure 6.12

or selected diameters of

Feeds

Set the direction of feed before you begin milling. Up milling, or conventional milling, is when the direction of feed is opposite to the direction of cutter rotation (Figure 22.2).

ing, or cl

ter r

otation.

Down mi of cut

Up milling.

fixture holding it, so fasten it securely. These forces also push the workpiece away from the cutter, which eliminates backlash. Up milling is advised for milling cast iron, softer steels, and other ducti

Down milling.

not sweep back into the cut. Setups are more rigid, an advantage when cutting thin workpieces held in a vise or workpieces held in magnetic chuck. Down milling also produces str because ther

imb milling, is when the direction of feed is the same as the direction

In up milling, forces on the workpiece tend to pull it out of the vise or

le materials. I

Down milling usually produces good surface finishes because chips do

aighter cuts. We recommend down milling when using carbide cutters

e is less wear on the cutting tool. In general, however, avoid it because of

n gener

al, it’s the best way to mill.

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the backlash problems associated with it.

Speeds and Feeds for Milling

Feed rates.

Your feed rate should be as high as your machine, cutting tool, workholding method, and workpiece can tolerate while giving a good finish. Feed rate is usually given in inches per minute (ipm). You determine feed rate by the speed of the cutter in rpm and the number of teeth in the cutter.

There are many factors to consider in selecting the feed per tooth, and there is no easy formula to follow. Here are several principles to guide you:

• Use the highest feed rate conditions allow

• Avoid using a feed rate below 0.001” per tooth

• Harder materials require lower feed rates than softer materials

• Feed wider, deeper cuts more slowly than narrow, shallow cuts

• A slower feed rate gives a better surface finish

• Never stop the feed before finishing the cut

ate in

ou know the feed in inches per tooth, use this formula to calculate table f

If y

eed r

inches per minute (ipm):

Ipm = ipt x N x rpm

Where ipt = inches per tooth, N = number of teeth in the milling cutter, and rpm = spindle speed of the mi

lling machine.

Milling

Down

Milling

Feed DirectionFeed Direction

Figure 22.1 In up milling (left), the workpiece feeds into the cutter in the opposite

direction of the cutter’s revolutions. In down milling (right), the workpiece

feeds into the cutter in the same direction as the cutter is turning.

Or V

isit www

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Midas 1220 XL Operator’s Manual

Material

Free-machining low carbon 1111

steel resulphurized 1112

Free-machining low carbon 10L18 steel leaded 12L14

Plain low-carbon steels1006

1026

Plain medium-carbon steels 1030

1095

Plain high-carbon steels

Tool Steels W1-W7

1060 1095

H20-H43 D1-D7

Brinell

Hardness

100-150 150-200

100-150 150-220

100-125 125-175

125-175 175-225

150-200 200-250 200-250

High-Speed-Steel

Cutters

120-160 120-180

100-225 110-250

80-150 80-140

80-140 60-110

70-120 60-110

80-120

40-85 30-60

Carbide

Cutters

400-600 400-900

250-500 250-600

300-600 250-500

250-500 225-400

250-450 225-400

300-350 175-300 100-200

Stainless Steel 302

430F

Gray Cast Iron

Aluminum Cold-drawn

Aluminum

Brass 360 free-cutting,

Bronze

ASTM Class 20 Through Scale Under Scale

wrought alloys

Casting Alloy

(as cast)

cold-drawn

220 commercial

annealed

Table 22.1 Recommended Cutting Speeds for Milling (fpm)

135-185 135-185

110-160

70-100

100-140

140-200 130-225

225-350 350-450

350-700 400-800

500-800 1000-1800

600-1000 1200-2000

300-500 600-1000

80-140 180-275

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Chapter 23

Common Milling Operations

Milling Flat Surfaces

One way to mill a flat surface is by plane milling (Figure 23.1). Adjust the milling cutter vertically to give the needed depth of cut while the workpiece is held on the table and slowly feed it horizontally. Every tooth on the periphery of the cutter removes a chip every revolution. Milling wide, flat surfaces this way is called slab milling.

Figure 23.1 One way to mill a flat surface is by plane milling.

ace mi

Or V

y f

isit www

l flat surf

y to mi

Another w operate at right angles to the cutter axis. Inserted-tooth face-milling cutters (Figure 23.2) face mill large surfaces.

Figure 23.2 Inserted tooth face milling cutters face mill large surfaces.

aces is b

lling. In this method, the cutter teeth

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Midas 1220 XL Operator’s Manual

Bevels and chamfers are cut at an angle to the main work-piece surface. A bevel cut (Figure 23.3) goes from side to side, completely removing the perpendicular edge. A chamfer removes only part of the perpendicular edge.

Figure 23.3 A bevel cut goes from side to side, completely removing the perpendicular edge.

To cut bevels and chamfers, either move the workpiece into an angular cutter or hold the workpiece at the desir hold the workpiece in a vise or in a fixture held in a vise.

ed angle whi

le moving it into a plain cutter or end mill. You may

Squaring a Workpiece

To square the ends of a workpiece, use the peripheral teeth of an end mill. If you want to remove a lot of material, use a roughing end mill first, then finish to size with a regular end mill.

Plunge cut end mill a predetermined width and depth, retract it, then advance and plunge it again

epeatedly. The maximum cutting force is in the machine's strongest (axial) direction.

ting is ef

ficient for removing material quickly on low horsepower. Plunge the

Milling a Cavity

After laying out the outline of the cavity to cut, rough it out to within 0.030" of the finished size before making finish cuts. Use a center-cutting end mill for the starting hole.

Tapping

Drill a hole. Then remove the drill bit and put a tap into the chuck. By turning the chuck slowly by hand with slight downward pressure, you can get a perfectly threaded hole.

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Smithy Midas 1220 XL Operator's Manual

Specifications and Main Features

Frequently Asked Questions

User Manual