SINGER 251 User Manual

Tlrm 20549

r:ev. (557)

SERVICE MANUAL

AND

PARTS LIST

FOR

SINGER

MACHINES

OF CLASS 251

SINGLE NEEDLE

LOCK STITCH

AUTOMATIC OILING SYSTEM

£275Si?

CAUTION—See that the oil reservoir is filled os instructe.d on page 6 before running the machine, even to test the speed. Special attention is olso called, to the hook lubricating instructions on page 7.

THE SINGER MANUFACTURING COMPANY

Copyright © 1957 by The Singer Manufacturing Company

•A Trade Mark of THE SINGER MANUFACTURING COMPANY

Printed in U. S. A.

FIG. 2. X-RAY VIEW OF MACHINES OF CLASS 251 (LUBRICATING SYSTEM SHOWN IN SOLID BLACK)

FOREWORD

This	book contains	complete information covering	operation,		adjustment,
parts list,	attachments and	special fittings for Machines of	Class	251-	Descriptions
and exploded vievYS of all		parts assemblies on pages 45 to 194		Inclusive, will be
found helpful when ordering any part of the machine requiring renewal.

DESCRIPTION

Machines of Class 251 produce top quality, straight-line, single-needle, lock stitching in fabrics as fine as ladies' lingerie or as heavy as mens' overcoating.

General Features

Federal Stitch Type #301.

High Speed (see chart on page 4). Maximum speed dependent upon nature of work and ability of operator.

Gear driven, lubricated. Rotary Sewing Hook on horizontal axis makes two revolutions for each stitch.

Automatic Lubricating System (see X-Ray							View		on
opposite page). Centrifugal Pump delivers							oil	under
pressure from		Reservoir	to	all	principal	bearings.			Oil
wicks	lubricate	bearing surfaces in head				end	of		ma­
chine	and return excess		oil	to	Reservoir.		Oil	Guard

covers entire path of Take-up Lever.

Oil Flow Window, in direct view of operator, reveals circulation of oil inside machine arm.

Upper	gears	are	spiral-bevel.	Lower	gears	are
hypoid-bevel.
Hook	Shaft	mounted	.160 inch	forward	of vertical
axis of Needle Bar for improved stitch formation.
Drop Feed guided by mounted journal					bearings	to
prevent side movement of Feed Dog.

Machine	Dimensions:		Bed		length		18-3/4		inches,
width 7 inches. Space at right of Needle 1 1 inches.
Machine	Head is	supported			by	Machine		Base		and
Oil Reservoir, designed to fit the cutout in table.
Machine	Pulley	147016.		Outside		diameter		of		belt
groove 2.90	inches	for	3/8	inch	V-belt.		Effective			diam­

eter for 5/16 inch round leather belt is 2-3/8 inches.

Length of stitch determined by a Push-Button Stitch

Regulator on top of machine arm.				Regulator		includes
Locking	Device	to prevent	changing	of	stitch	length
during	machine	operation:	(For	maximum		possible
.stitch length, see chart on page 4).				Stitch	Length Indi­
cations on Machine Pulley are in view of operator.

When the machine is in operation, the		top of	the
machine pulley must always turn	over	toward	the
operator.
Knee Lifter, regularly furnished, is	an	integral	part
of the Machine Base and Reservoir.

SPECIAL CHARACTERISTICS OF

MACHINES OF CLASS 251

MACHINES (CLASS AND VARIETY)

		251-1	251-2	251-3	251-3 (HEAVY)
	TYPE OF	Light-Weight	Medium-Heavy	Heavy to	Extra-Heavy to
	MATERIAL		to Light-Weight	Light-Weight	Light-Weight
	MAXIMUM
	SPEEDt	5000	5000	4300	4300
	(R.P.M.)
	MAXIMUM	7	5-1/2	5-1/2	5-1/2
	STITCH
		per inch	per inch	per inch	per inch
	LENGTH
	NEEDLE BAR
	STROKE	1-9/64	1-13/64	1-7/16	1-7/16
	(Inches)
	PRESSER BAR	9/32
	LIFT		5/16	3/8	7/16
	(Inch)
	NEEDLES:
	CLASS	88 X 9	16 X 257	16 X 257	16 X 261
	AND
	VARIETY
	SIZES	8, 9,10,11,12,	8, 9, 10, 11, 12, 13,	8, 9, 10, 11, 12,
	RECOM­	13, 14, 16,	14, 16, 17, 18, 19,	13, 14, 16, 17,	16, 18, 19, 21,
	MENDED	17, 18, 19,	20, 21,22, 23 and	18, 19, 20, 21,	22 and 23
		20, 21 and 22	24	22, 23 and 24

fDependent upon nature of material and ability of operator.

SETTING UP

TABLE

CUT-OUT

Fig. 3. Installation of Machine	Fig. 4. Installation of Knee
on Base	Lifter on Machine Base

When

shipped,

the

base

is held to

the

machine

by

a single bolt through the bottom

of

the

base.

Discard

this

bolt

and

plug

the hole

by

inserting

from

inside

the

base,

the

special

cap

screw

K,

Fig.

3,

furnished

with the machine.

The

base

fits

into

a

standard

table

cut-out,

as

shown

in Fig. 3 and rests on the

four

corners

without

fastening.

Rasp

the

edges

of

the

cutout,

if

necessary,

as

the

base must slide in without driving and must

be

located

so that the machine head does not touch the table

when it is placed on the base.

Use

shims

on

the

corners,

if

necessary,

to

prevent

the

base

from

rocking.

The

base

should

also

be

level

in both directions so that the oil level will be accurately indicated by the marks in the base.

See that the plunger L, Fig. 3 is in place inside the base, before putting the machine on the base.

The machine head rests on the cork gasket in the

base and is not fastened. The machine hinges must

not support the head except when it is tilted back.

The

knee lifter

is

shipped

assembled

to

the base,

except

for

the

knee

plate

and

lever

J,

Fig.

4.

After

the base is in position,

loosen

the

set

screws

D

and E,

Fig.

4

and

slide

the

shaft

forward

to

the

position

shown

in Fig. 4. Attach the knee

lifter lever

J.

Set

the

stop screw F so that there is only a

little

play

of

the

lifter

before it starts to lift the presser

bar,

then

hold

the

screw

and

tighten

lock

nut

G.

Set

the

rear

stop

dog

H to

allow the presser bar to

be

just

raised

to

its

limit

but

not

enough to

permit further

strain

on

the

knee

lifter

parts

or

to

permit

the

action

of

the

knee

lifter

to lift the machine from its base.

CAUTION:—Before starting the machine, it must be

thoroughly

oiled,

in

accordance

with

the

instructions

on page 6.

SPEED

The	maximum		speed	recommended		for		Machines		It is advisable to operate these machines at a more
251-4	and	251-2 is 5000 revol			utions	per	minute		and	moderate speed the first few days, after which they
for Machine 251-3, 4300 revolutions per							minute		ac­	can be operated at maximum speed.
cording	to	the	material	being	sewn and		the	type	of
work being done. (See chart on opposite page.)

LUBRICATION

TURN BACK MACHINE

NEVER ALLOW	FILL TO
OIL TO FALL	HIGH MARK
BELOW LOW MARK
Fig. 5. Oil Reservoir	Fig. 6. Oil Flow Window

Machines

of

Class

251

have

an

automatic

lubricat­

ing system in which oil is

circulated by means of a

centrifugal

pump

from

a

reservoir

in

the

base.

X-Ray

view of machine on page

2

illustrates

automatic

cir­

culation of oil in this machine.

BEFORE

STARTING

THE

MACHINE

the

oil

reservoir

must

be

filled with

"TYPE

A" or "TYPE C" OIL, sold

by

Singer

Sewing

Machine

Company.

"TYPE

C"

OIL

is used when an oil is desired which

will

produce a

minimum

of

stain

on

fabrics,

even

after

a

long

period

of storage.

Tip the machine back on

its

hinges

and

fill

the

oil

reservoir as instructed in Fig. 5,

When a machine is NEW or has been idle for several

weeks it

is

advisable

to

remove

the

face

plate

and

oil

the needle bar and take-up

bearings. Oil the hook as­

sembly

by

hand

and

check

the

oil

flow,

as

instructed

on page 7. The automatic oiling system will function efficiently, after the first few minutes and continue to lubricate all bearings.

When	in	operation,			the	oil	level	in	the	reservoir
should be inspected				at	least	twice a month			or	as	oftei^
as necessary,		to	keep		it from		going	below		the	LOW
mark, see Fig. 5, in the reservoir.
CAUTION: Correct lubrication is indicated by a con­
tinuous	stream		of	oil	passing		the	oil	flow		window
while machine is running, as shown in Fig. 6.
Should	this	oil		flow	become		erratic,	STOP		the ma­
chine and do not run					the	machine again			until		the oil
flow has been restored.

At least twice each month check the oil level in the

reservoir.

Never allow oil level to drop below LOW mark, shown in Fig. 5.

Oil	your	bobbin	winder	occasionally		by	applying
a few	drops	of oil	to the	oil	well in bobbin		winder,
as shown in Fig. 15, page 12.
See	instructions,		covering	Oil	Removing	Wick As­
sembly, on pages 38 to 41.

ADJUSTMENT OF ROTATING HOOK OIL FLOW REGULATOR

Fig. 7. Oil Flow Regulator in Hook Shaft Bushing

The

sewing

hook

is

automatically

lubricated.

The

flow

of

oil

is

controlled by

Oil

Flow Regulator

140551,

Fig. 7.

The

Oil

Flow

Regulator

140551 is

set

at the

factory

for

automatic

lubrication

of

the

hook

under

overage

sewing conditions.

Turn Regulator Thumb Screw (see 140551, Fig. 7)

clockwise to increase the flow

of

oil

to the

hook as

indicated by the (-|-)

sign

under

its

arrow

on

the

head

of the thumb screw.

Turn Regulator Thumb Screw counterclockwise to

decrease

the flow,

as indicated

by

the

(~)

sign

under

its arrow on the head of the thumb screw.

To

determine

whether

the

oil

is

properly

flowing

to

the

hook,

withdraw

the

bed

slide

and

hold

a

piece

of

thin paper under the hook

while

the

machine

runs for ten seconds. There

should be

a

pattern

of three

oil

sprays

on the paper; two light

lines

on

the

outside

and

one

heavier

spray

in

the

center.

If

there

is

no

trace

of

oil or an excessive amount

of

oil

on

paper,

adjust the Oil Flow Regulator, as

instructed

above,

or

replace the oil filter 143350, Fig. 7,

in

the

head

of

the

hook shaft, as instructed on page 28.

HINTS FOR PERFECT OPERATION

If

the sewing

hook

should

become

excessively

warm,

it may

be

due

to

an

insufficient

supply

of

oil

to

the

hook

(see

instructions,

above,

for

adjusting

Oil

Flow

Regulator).

Keep

the

oil

level

in

the

oil

reservoir

at

the

HIGH

mark.

Clean

out

any

lint

or other waste around the

hook,

around

the

needle

slot

in

the

bobbin

case

holder

and

between the

feed

rows on

the

under side

of

the

throat plate.

Clean

out

any

lint

or other foreign matter that

may

have

collected

around

oil

return

passages, particu­

larly at oil return hole in rear arm shaft bushing.

When

in

operation,

the top of the machine

pulley

must always turn over toward the operator.

Always		keep	the bed		slides	closed	when	the	ma­
chine Is in operation.
Do	not	run	the	machine with		the presser foot resting
on the feed without some fabric under the presser foot.
Do not run the machine when both bobbin								case	and
needle	are	threaded unless there is material						under	the
presser foot.
Do	not	try	to	aid the machine by			pulling	the	fabric
lest you bend the needle. The machine feeds								the	work
without assistance.
NEVER		TOUCH		THE	STITCH	REGULATOR		PLUNGER

WHILE THE MACHINE IS RUNNING.

NEEDLES

The size

of

the

needle

to

be

used

should be deter­

mined

by

the

size

of

the

thread

which

must

pass

freely through the eye of

the needle. Rough or uneven

thread,

or

thread

which

passes

with

difficulty

through

the

eye

of

the needle, will interfere with the successful

use

of

the

machine.

(See

chart on page 4 to determine

Size as well as Class and Variety of needle required.)

A

bent

needle

may

cause

the

machine

to

skip

stitches,

or

it

may

make

it difficult for the operator

to

keep

a

perfectly

even

margin.

In

many cases,

a

run­

off will take place.

A

hook

or burr on the needle point will

result

in

o

finish

that

looks

blurred

and

when

short

stitches

are

used (20 to 22 per inch), some materials may be cut.

Check needles often to make sure that defects are

not present.

Orders for needles must specify	the	Quantity re­
quired, the Size number, also the	Class	and Variety
numbers, separated by an x.

The following is an example of an intelligible order;

"100 No. 16, 88 X 9 Needles."

The	best stitching		results		will be obtained by using
needles sold by Singer Sewing Machine Company.
The	above	needles		are	regularly	furnished with
nickel	finish	but	are	also	available	with chromium

finish if so ordered.

TO SET THE NEEDLE

Turn	the	machine		pulley		over toward			the	operator
until the needle bar moves to its highest point.
After	loosening		needle		set	screw,		insert needle UP
into needle bar			AS	FAR	AS	IT	WILL	GO,	as instructed
in Fig, 8.
The	single	continuous			groove		of	the	needle	MUST

face the left end of the machine, as shown in Fig. 8.

Securely tighten needle set screw.

NOTE: The	needle is held in place, in	Machines	251-2
and 251-3,	by means of a needle clamp,	instead	of the
set screw in needle bar shown in Fig. 8.

MOVE TO

-^-HIGHEST ' POINT

LOOSEN

SCREW

INSERT

NEEDLE UP

AS FAR AS

POSSIBLE

Fig. 8. Setting the Needle

(Mochine 251-1 )

THREAD

On Machines of Class 251-					use	only	left	twist
thread	in the	needle.	Either	right	or	left	twist	thread
can be used in the bobbin.
To	determine	the	thread	twist,	hold	the	thread as

shown		in Fig.	9.	Then	roll the	thread	over	toward	you—
if	the	strands	of	the	thread	wind	tighter, the thread
is	left	twist;	if	the	strands	unwind	or	separate,	the

thread is right twist.

RELATIVE SIZES OF NEEDLES AND THREAD

The following sizes of needles and thread are recommended according to the class of work:

SIZES		SIZES OF
OF	CLASSES OF WORK	COTTON, LINEN
NEEDLES		OR SILK
8 to	Shirtings, Sheetings, Calicoes, Muslins, Silks, Dress	60 to 80 Cotton
14	Goods and all classes of general work with light	A and B Silk
	and medium weight fabrics.
16	All kinds of heavy Calicoes, light Woolen Goods,	40 to 60 Cotton
and	heavy Silk, Seaming, Stitching, etc.	C Silk
17
18	Tickings, Upholstery, Woolen Goods, Trousers, Boys'	30 to 40 Cotton
	Clothing, Cloaks, etc.	D Silk
19	Heavy Woolens, Tickings, Bags, Heavy Coats,	20 to 30 Cotton
and	Trousers, Heavy Clothing generally.	E Silk
20		60 to 80 Linen
21 to	Bags, Coarse Cloths and Heavy Goods.	1 6 to 20 Cotton
24		40 to 60 Linen

1 0

UPPER THREADING

Fig. 10. Upper Threading

Fig. 11. Threading the Needle

First, turn the	machine	pulley over	toward	the	oper­
ator until needle	is at	Its highest	point,	then	pass
the needle thread from the unwinder through the

threading points in the order shown in Figs. 10 and 11.

Draw about two inches of thread through the eye of the needle with which to start sewing.

1 1

TO REMOVE THE BOBBIN

1. MOVE

TAKE-UP

TO HIGHEST

POINT

Turn	machine pulley			over toward			operator,
until needle thread take-up					lever	is	at highest
point, as shown in Fig. 12.
Reach		beneath	bed	of	machine		with	left
hand	and	remove	bobbin,		as	instructed		in

Figs. 13 and 14.

Fig. 12. Preparation

2. OPEN LATCH

3. HOLD LATCH AND PULL CASE FROM HOOK

Fig. 13. Removing Bobbin Case from Sevving Hook

4. RELEASE LATCH \

NOTE: While latch is kept open, bobbin will be retained in bobbin case.

To remove bobbin from the bobbin case, release latch and turn open end of bobbin case downward. Bobbin will drop out, as shown

in Fig. 14.

5. BOBBIN 1 DROPS ▼ OUT

Fig. 14. Removing Bobbin

12

TO WIND THE BOBBIN

See Fig. 15

Fasten

bobbin

winder to table with its driving

pulley

in

front

of

the

machine belt, as shown above, so

that

bobbin

winder

driving

pulley

will

make

firm contact

with

machine

belt

when

thumb

latch

is

pressed

down

and

pulley

will

be

released

from

contact

with

belt

when

sufficient

thread

has been

wound

upon

the

bobbin.

Place

bobbin

on

spindle,

pushing

it

on

as

far

as

it

will go and pass thread

through

threading

points,

as

shown above.

Wind

end

of

thread

around the bobbin a few

times.

Press

down

on

thumb

latch,

pushing

driving

pulley

over against belt, as shown in Fig. 15. Start machine.

Bobbin

winder

will

stop

automatically,

when

the

amount of thread for which it is regulated is wound

upon the bobbin. For more

thread

on

bobbin,

turn

screw

L

inward;

for less

thread

on

bobbin,

turn

screw L outward.

When

winding

a

bobbin

with

fine

thread,

a

light

tension

should

be

used.

Adjust

the

knurled

nut

U, Fig. 15, to regulate the tension.

If

thread

winds

unevenly

on

bobbin,

loosen

screw T

and

move

tension

bracket

Z

to

the

left

or

right,

as

required. Tighten screw T.

Bobbins can be wound while the machine is stitching.

NOTE; Occasionally	apply a	few	drops	of oil	to the
oil well, shown in	Fig. 15,	on top	of the	bobbin	winder
frame.

1 3

TO THREAD THE BOBBIN CASE

Hold the bobbin so that the thread will unwind in the direction shown in Fig. 16.

Hold the bobbin case as shown In Fig. 16 and place the bobbin into it.

/ \

SLOT

NEAR

TOP

I /

Fig. 16. Placing Bobbin

in Bobbin Case

Pull the thread into the slot 1 and under

the tension spring 2, Fig. 17.

3. DRAW THREAD

Draw the thread into the delivery eye at the end of the tension spring, as shown in Fig. 18.

Fig. 18. Drawing the Thread

Under the Tension Spring

1 4

TO REPLACE THE BOBBIN CASE

TO PREPARE FOR SEWING

1.REPLACE BOBBIN CASE ON STUD

V

3. PRESS BACK

UNTIL LATCH CATCHES GROOVE IN STUD

Fig. 19. Bobbin Case Threaded

and Replaced

After

threading,

take

bobbin

case

by

latch

in

the

left

hand

and

place

bobbin

case

on

center

stud

of

bobbin

case

holder,

as instructed

in

Fig.

19.

Release

latch.

Press

bobbin

case

back

until

latch

catches

groove near end of stud. Allow

about

two

inches

of

thread to hang free.

TO PREPARE FOR SEWING

Hold

slack

end

of

needle thread loosely and turn

machine

pulley

over

toward

you

until

needle

moves

down

and

up

again

to

its highest point, catching bob­

bin

thread.

Draw

up

needle

thread;

bobbin

thread

will come up with it

through

hole

in

throat

plate,

as

shown in Fig. 20. Lay

both

threads

back

under

presser

foot.

Fig. 20. Drawing Up the Bobbin

Thread

TO START SEWING

Place material beneath the presser foot and start to sew, turning the machine pulley over toward you.

TO REMOVE THE WORK

1.Let the thread take-up lever rest at its highest point.

2.Raise the presser foot.

3.Draw the work toward the rear until it is clear of the needle.

4.Cut the threads close to the goods.