Hitachi WR12DMB, WH12DMB Service Manual
POWER TOOLS
TECHNICAL DATA
AND
SERVICE MANUAL
CORDLESS IMPACT DRIVER
WH 12DM
CORDLESS IMPACT WRENCH
WR 12DM
SPECIFICATIONS AND PARTS ARE SUBJECT TO CHANGE FOR IMPROVEMENT
LIST Nos. WH 12DM: F862
WR 12DM: F864
Oct. 2001
W
MODEL
WH 12DM
WH 12DM WR 12DM
WR 12DM
EB1220BL
2.0Ah
W
H
12D
M
EB1220BL
2.0Ah
W
R
1
2D
M
REMARK:
Throughout this TECHNICAL DATA AND SERVICE MANUAL, a symbol(s)
is(are) used in the place of company name(s) and model name(s) of our
competitor(s). The symbol(s) utilized here is(are) as follows:
Symbol Utilized
Competitor
Company Name
Model Name
C MAKITA
6916D
WH 12DM
Symbol Utilized
Competitor
Company Name
Model Name
C MAKITA
6918D
WR 12DM
Page
CONTENTS
1. PRODUCT NAME...........................................................................................................................1
2. MARKETING OBJECTIVE .............................................................................................................1
3. APPLICA TIONS..............................................................................................................................1
4. STANDARD EQUIPMENT ..............................................................................................................1
5. SELLING POINTS ..........................................................................................................................2
5-1. Selling Point Descriptions .............................................................................................................. 4
6. SPECIFICATIONS ........................................................................................................................14
6-1. Specifications............................................................................................................................... 14
6-2. Optional Accessories ................................................................................................................... 15
7. COMPARISONS WITH SIMILAR PRODUCTS............................................................................18
7-1. Specification Comparisons (Cordless Impact Driver) .................................................................. 18
7-2. Specification Comparisons (Cordless Impact Wrench) ............................................................... 19
7-3. Tightening Torque ........................................................................................................................ 20
7-4. Tightening Speed......................................................................................................................... 23
7-5. Number of Screws or Bolts Driven............................................................................................... 24
7.6 Actual Noise When Tightening Wood Screws and Bolts ............................................................... 25
8. PRECAUTIONS IN SALES PROMOTION ...................................................................................26
8-1. Safety Instructions ....................................................................................................................... 26
8-2. Tightening Torque Inspection Prior to Operation ......................................................................... 28
8-3. Tightening Torque V ariation ......................................................................................................... 28
8-4. Suggestions and Precautions for the Efficient Use of the Charger.............................................. 29
9. OTHER PRECAUTIONS ..............................................................................................................30
10. REPAIR GUIDE ..........................................................................................................................31
10-1. Precautions in Disassembly and Reassembly........................................................................... 31
10-2. Precautions in Disassembly and Reassembly of Battery Charger ............................................ 38
11. STANDARD REPAIR TIME (UNIT) SCHEDULES......................................................................39
Assembly Diagram for WH 12DM
Assembly Diagram for WR 12DM
--- 1 ---
1. PRODUCT NAME
Hitachi Cordless Impact Driver, Model WH 12DM
Hitachi Cordless Impact Wrench, Model WR 12DM
2. MARKETING OBJECTIVE
Owing to the shift of demand from nails to screws and increased demand for long screws, there is a market need
for a powerful, high-speed, compact and easy-to-handle impact driver that provides more efficient operation per
charge. The new cordless impact driver Model WH 12DM ("Super Impact 12") is the upgraded version of the
previous Model WH 12DH, developed under the concept for more compact, powerful and convenient model to
plainly differentiate it from the competitors. Thanks to the new development/production technologies such as
computer analysis for optimum impacting operation and air ducts, 3-D CAD engineering and mold designing,
double-layer molding, blow molding and the new rare-earth magnet motor, the Model WH 12DM provides the
following features to respond to the user requests:
•
30% higher speed than the previous model
•
Convenient functions including hook and bit holder
•
High durability
•
New-type flat battery
•
Comfortable handle grip
The new cordless impact driver Model WH 12DM ("Super Impact 12") is the standard model of the Super Impact
series. This "Super Impact 12" is expected to expand our market share of the cordless impact products. The new
cordless impact wrench Model WR 12DM ("Super Wrench 12") is also brought out. The Model WR 12DM has the
maximum tightening torque of 150 N•m. It is substantially higher than the previous Model WR 12DH and
equivalent to the tightening torque of our higher-class 14.4-V cordless impact wrench.
3. APPLICA TIONS
•
Tightening/loosening of small screws, tapping screws, wood screws, bolts, nuts, etc.
•
Drilling into wood and various other materials (with use of optional accessory drill chuck adapter).
[Applicable Markets]
•
Wood-product assembly: Tightening/loosening of wood screws.
•
Construction industry: Assembly of scaffolding, roofing, aluminum sashes, fencing, etc.; removal of plastic cones
from concrete forms, mounting/removal of form ties; drilling into the wood frames of concrete forms, etc.
•
Manufacturing industry: Assembly work for automobiles, rolling stock, shipbuilding, agricultural machinery and
tools, industrial machines, steel furniture, etc.
•
Utility industry: Assembly and installation of electric equipment, plumbing facilities, air conditioning (duct
assembly, etc.), sanitary fixtures and various other facilities.
•
Service industry: General repair work; installation of advertising aids, automobile repair, assembly of garages
and carports storage sheds, etc.
•
Various other assembly, construction or repair facilities.
4. STANDARD EQUIPMENT
The Models WH 12DM and WR 12DM come standard with the new-type flat battery.
(1) BL K specification: One EB 1220BL battery (NiCad, capacity 2.0 Ah), UC 14YF2 charger and case
(2) 2BLFK specification: Two EB 1220BL batteries (NiCad, capacity 2.0 Ah), UC 14YF2 charger and case
(3) HLFK specification: One EB 1230HL battery (NiMH, capacity 3.0 Ah), UC 14YF2 charger and case
(4) 2HLFK specification: Two EB 1230HL batteries (NiMH, capacity 3.0 Ah), UC 14YF2 charger and case
--- 2 ---
EB1220BL
2.0Ah
WH 12DM
5. SELLING POINTS
(1) Cordless Impact Driver: WH 12DM
High durability
• High durability in continuous operation
(improved cooling efficiency):
Temperature rise is reduced to half of C
thanks to the 1.4 times thicker winding
(than C), powerful rare-earth magnet motor
(made in Hitachi Koki), large fan and
optimum air ducts.
• Improved dust resistance:
Ball bearings with contact seals
Labyrinth construction
• Long service life:
The gears and the motor section are
strengthened to realize powerful operation.
Ultra-compact body but class-top tightening speed
(30% faster than the previous model, 10% faster than C)
Maximum torque 100 N•m, the same torque in forward/
reverse rotation
Enhanced maintainability
• Singly replaceable armature
• Replaceable carbon brushes
Stepless variable speed switch
Startup speed is decreased to 20
rpm to prevent screws from falling
sideways.
Compact and stable flat battery
• Selectable from three types:
high-capacity NiMH battery, light-weight
NiMH battery and NiCad battery
• Conventional stand-up batteries (EB 12B, etc.)
are also usable.
1.5 times
higher
capacity
NiCad
Conventional
batteries are usable
(B-type batteries).
Powerful
Low operating noise
Powerful tightening thanks to
the large hammer
Noise level of the Model
WH 12DM compared with the
previous model
• When tightening wood
screws: -3 dB
• When tightening bolts: -4 dB
Comfortable handle grip
Shaped to comfortably fit
the operator's thumb
Slim grip
Soft and slip-resistant grip
(Two kinds of resins are firmly
adhered by fusion in the new
double-layer molding process,
M-DSI)
Convenient
Convenient one-touch hook
Quick slide-out hook (angle-adjustable)
Mountable on either side
Bit holder
New, compact and cyber design
Overall length of the Model WH 12DM
compared with the previous model
Overall length: -9 mm
Girth of housing: - 10 mm
Height: - 19 mm
Weight: - 80 g
Handle angle is changed from 5˚ to 10˚
(easy to handle).
Patent applied for
Interchangeable
Rubber cap and soft material
To protect the main body
and the workpiece, and to
prevent slipping
--- 3 ---
EB1220BL
2.0Ah
WR 12DM
Selling points common to the
Model WH 12DM
• Newly designed compact body
• Ergonomically designed comfortable
handle (slip-resistant double-molded
grip)
• Convenient one-touch hook
• Stable flat battery (interchangeable)
• High durability, dust resistance and
long service life
(2) Cordless Impact Driver: WR 12DM
Compact body
Overall length of the Model
WR 12DM compared with the
previous model:
WR 12DH: -8 mm
C: -3 mm
Powerful tightening torque 150 N•m (1530 kgf•cm, 1330 in-lbs.)
WR 12DH: 118 N•m (1200 kgf•cm, 1040 in-lbs.)
C: 120 N•m
WR 14DH (14.4-V product): 147 N•m (1500 kgf•cm, 1302 in-lbs.)
--- 4 ---
5-1. Selling Point Descriptions
Common selling points (Models WH 12DM and WR 12DM)
(1) New, compact and cyber design
The Models WH 12DM/WR 12DM have vibrant and cyber looks thanks to the widely adopted soft urethane
resin (elastomer) and the complicated 3-D curved surfaces, stirring up curiosity to touch them.
The Models WH 12DM/WR 12DM are equipped with a separate-type motor in which the armature is
separated from the magnet like a 100-V motor while the previous models are equipped with an integratedtype motor contained in a steel case. Thanks to the new separate-type motor, the steel case is eliminated
and the motor section is downsized. In addition, the hammer case is downsized. The overall length of the
Models WH 12DM/WR 12DM is shortened by 9 mm, the girth is shortened by 10 mm and the height is
shortened by 19 mm in comparison with the previous models as shown below. The Models WH 12DM/
WR 12DM are convenient for working in narrow places.
The weight of the Models WH 12DM/WR 12DM is heavier than C by about 80 g because they are equipped
with the hook, and the gears and the motor are strengthened to enhance the durability and the
performance.
The Models WH 12DM/WR 12DM are easy to handle and well balanced thanks to the change of the handle
angle from 5˚ to 10˚ to cope with the user demand (C: 15˚). This is the optimum angle determined in the
factory by making sample machines.
(2) High durability
Owing to the shift of demand from nails to screws and increased demand for long screws, impact drivers
having high heat resistance in continuous operation are much sought after. However, there are problems such
as heavy noise or vibration of the ball bearings and decrease in power if the impact drivers are used harshly in
dusty environments. In addition, higher strength and longer service life are required to continuously tighten
and loosen bolts in scaffolding and demolishing works. The Models WH 12DM/WR 12DM have high durability,
dust resistance and long service life in continuous operation as described below.
--- 5 ---
1 Enhanced heat resistance of the motor (Example: When tightening M12 bolts continuously (Cycle of
operation: 5-second impacting and 10-second stopping, 3.0 Ah battery used)
The heat resistance comparison between the Models WH 12DM/WR 12DM and C is shown below. The
Models WH 12DM/WR 12DM are equipped with a powerful motor having 9% larger core diameter, 13% larger
stacking length, 1.4 times thicker winding (2 times larger cross section of the conductor) and 33% larger
volume of the armature than C. The cooling efficiency is improved and the temperature rise is reduced to half
of C (when using two batteries) thanks to the powerful full-fledged large radial fan and the computer-analyzed
air ducts. Thus the Models WH 12DM/WR 12DM are protected from burnout due to long-time continuous use
and decrease in speed due to temperature rise. The motor is manufactured using the latest facilities in
Yamagata Plant.
0
50
100
150
200
250
C
HITACHI WH 12DM
Temperature
1 battery
2 batteries 3 batteries
Burnout
C: Smoking
As shown in the above graph, C produces smoke when operating on one battery. When tightening wood
screws (5.3 mm diameter and 120 mm long) into a workpiece (hemlock spruce) continuously, it suddenly takes
much time to tighten the tenth and the later screws. This is because thin wires used in the armature assembly
of C are apt to produce heat and the cooling construction is insufficient to reduce the heat.
Flow of cooling air around the armature
Large radial fan
Air inlet Air outlet
--- 6 ---
2 Improved dust resistance
The dust-resistant contact seal bearings are provided at the commutator side and the fan side. Thanks to the
new bearings, hermeticity is enhanced because the seals of the bearings always contact the inner rings (C:
non-contact bearings). The labyrinth construction is provided between the housing and the fan at the pinion
side as shown in the figure below to ensure protection against dust because the pinion side must have high
durability against heavy loads. The air inlet is minimized and the powerful fan discharges dust if entered.
Seal
Dust resistance is improved
thanks to the contact seal
bearings.
The labyrinth
construction ensures
protection against dust.
Labyrinth
3 Improved service life and durability
Although the service life may vary depending on the frequency of use and the severity, the service life of the
Models WH 12DM/WR 12DM is 1.5 times longer than C in spite of the compact body because the Models
WH 12DM/WR 12DM have strong components such as the highly durable motor and the gears made of
specially heat-treated steel to realize powerful operation.
--- 7 ---
(3) Convenient one-touch hook
A hook is very convenient if there is no place to put the impact driver temporarily. Although various kinds of
hooks are on the market, there is a user demand for a standard accessory hook. To cope with this demand,
the Models WH 12DM/WR 12DM are equipped with the hook having the following features as a standard
accessory.
1 The hook can be quickly slid out and can be slid in when not needed.
2 The hook is mountable on either side to cope with the use by either right-handed persons and left-handed
persons. The mounting position can be changed by using a flat-blade screwdriver or a coin.
3 The angle of the hook is adjustable in five steps (0, 20, 40, 60 and 80˚). The hook can be adjusted to
the optimum position according to the weight of the bit in use.
4 The bit holder that can contain a 65-mm double-ended bit is provided. It is very convenient for holding a
spare bit.
(4) Ergonomically designed comfortable handle
When the previous model is continuously operated, the housing tail rubs the base of the operator's thumb
and gives pain to the operator. To cope with this problem, the Models WH 12DM/WR 12DM are equipped
with the separate-type motor without case to make the housing tail section slim.
More delicate speed control is required at the start of tightening screws. The Models WH 12DM/WR 12DM
have a grip whose circumference at the switch section is shorter than C for ease of operation (grip
circumference at the switch section with respect to C: -14 mm).
The grip of the Models WH 12DM/WR 12DM is soft, slip-resistant and comfortable thanks to the soft resin
(elastomer) covered on the handle. The new double-layer molding process, M-DSI (Multi-layered Die Slide
Injection) is introduced to mold the nylon resin and the elastomer resin continuously in the same die. Since
the elastomer resin is molded while the formerly molded nylon resin is still hot, they are adhered by fusion
and the adhesion is so firm as to be torn if you try to remove the soft material layer from the nylon resin
layer.
Bit holder
Mountable on either side
Angle-adjustable in five steps
(0, 20, 40, 60 and 80˚)
Quick slide-out type
--- 8 ---
* M-DSI (Abbreviation of "Multi-layered Die Slide Injection")
This is a molding process that allows the nylon resin and the elastomer resin to be molded continuously in
the same die in a short cycle by sliding the die. The nylon resin and the elastomer resin are adhered by
fusion because the nylon resin is covered with the elastomer resin while it is still hot, and thus the firm
laminate can be made (manufactured using the latest facilities in Yamagata Plant).
(5) New flat battery (interchangeable)
There are user requests for a new cordless impact driver that can stand upright stably and can also be
operated on the conventional batteries (chargers). The new flat batteries for the Models WH 12DM/WR 12DM
have low height and wide bottom enough to stand the Models WH 12DM/WR 12DM upright and are
interchangeable with the conventional stand-up batteries including EB 12B.
Thumb
joint
WH 12DM
Short grip
circumference at
the switch section
Soft and slipresistant grip
Previous model
Slim tail section
(6) Low operating noise (-3 dB with respect to the previous model)
Although the previous models give shrill noise, the operating
noise of the Models WH 12DM/WR 12DM is low and dull thanks
to the large hammer and the optimized impact timing without
increasing the revolution. Thus the large hammer tightens
screws powerfully with low operating noise. (Refer to page 25 for
details.)
(7) Enhanced maintainability
The carbon brushes are replaceable and the armature is singly
replaceable thanks to the separate-type motor like a 100-V motor.
1.5 times higher capacity
NiCad
Conventional
batteries are usable
(B-type batteries).
--- 9 ---
(8) Others
The Models WH 12DM/WR 12DM have the following features common to the previous models.
The thickness of the silver plating over the terminal is changed from 3 µ to 30 µ (10 times thicker) for longer
service life of the terminal. In addition, the terminal is movable according to the movement of the battery to
prevent damage to the contact portion. The contact between the housing and the battery is changed from
line contact to surface contact to minimize rattling due to wear.
To cope with the initial galling of the anvil, a hardened-steel metal with an oil groove for retaining grease
(C: powder-sintered, no groove) is provided at the tip and a dust-resistant seal is provided inside the metal
(the effect has already been proved by the Model WH 12DC2).
[Reference] Motor comparison of the Model WH 12DM with C is shown below. The Model WH 12DM is
equipped with a powerful motor having 1.4 times thicker winding, larger core diameter and stacking length
than C. In addition, the Model WH 12DM is equipped with the full-fledged fan having walls at both sides of
a blade for powerful cooling while C's fan is simple with only the blades.
HITACHI WH 12DM
C
Outside diameter of core: 30.5 mm
Stacking length of core: 17.0 mm
Diameter of winding: 0.85 mm
Outside diameter of core: 28.0 mm
Stacking length of core: 16.0 mm
Diameter of winding: 0.6 mm
114 g
87 g
--- 10 ---
HITACHI WH 12DM
HITACHI WH 12DH
C
6.5 sec.
Model
5
sec.
9.5 sec.
7.2 sec.
67
8
9
4
3
21
10
Fast Slow
* Tightening time may vary depending on hardness of the workpiece, ambient temperature, characteristics
of the battery, etc.
Maximum tightening torque: 100 N•m {1020 kgf•cm, 885 in-lbs.}
The Model WH 12DM is equipped with a powerful motor having 33% larger volume of the armature and 1.4
times thicker winding (2 times larger cross section of the conductor) than C to reduce temperature rise.
Because the tightening torque is the same in both forward and reverse rotations, the tightening torque is not
reduced even when loosening bolts (this is the same feature in the previous models). C's speed and
tightening torque in reverse direction are lower than those in forward direction because the position of the
motor brush is shifted to obtain high power with the small motor.
Selling points of the Model WH 12DM
Class-top tightening speed
The Model WH 12DM is equipped with the new rare-earth magnet motor that is more powerful than the
previous model by 30% and the 35% larger hammer. With the computer analysis, the Model WH 12DM gives
optimum impact at tightening screws and the tightening speed is 30% higher than the previous model (10%
higher than C). The Model WH 12DM can also tighten long screws at high speed even into a hard wood
workpiece. Tightening time comparison of the Model WH 12DM with C is shown below. (Refer to pages 23
and later for detailed data on the tightening time and the working capacity.)
Tightening time comparison (Wood screw: 5.3 mm dia. x 120 mm length, hemlock spruce)
--- 11 ---
0
200
(174 in-lbs)
400
(347 in-lbs)
600
(521 in-lbs)
800
(694 in-lbs)
1000
(868 in-lbs)
1200
(1042 in-lbs)
kgf•cm
0
20
100
80
60
40
120
140
160
N•m
1400
(1215 in-lbs)
1600
(1389 in-lbs)
WR 12DM
122
WR 12DH
C
200
180
2000
(1736 in-lbs)
1800
(1562 in-lbs)
160
114
Fig. 1
Selling points of the Model WR 12DM
Powerful tightening torque 150 N•m {1530 kgf•cm, 1330 in-lbs.}
The Model WR 12DM is equipped with the new rare-earth magnet motor that is more powerful than the
previous model by 30% and the 35% larger hammer. With the computer analysis, the Model WR 12DM gives
optimum impact at tightening bolts and the tightening torque is 27% higher than the previous Model WR 12DH,
25% higher than C, and equivalent to the 14.4 V-product Model WR 14DH. The Model WR 12DM is
mechanically strong thanks to the high-strength components such as the 30% stronger anvil and the specially
heat-treated gears to realize powerful operation. Data of measured tightening torque are shown below.
(1) Tightening torque comparison
It should be noted that a M16 F10T bolt was tightened in 3 seconds with a hexagon socket (40 mm long) in the
test. The tightening torque of the Model WR 12DM is substantially higher than the previous model.
* The data above are intended for reference purposes only because actual tightening torque will vary
depending on tightening conditions.
To describe the merit of high tightening torque, the comparison data among the Model WR 12DM, the previous
Model WR 12DH and C are shown in Figures 2 and 3. Figure 2 shows the time required for loosening a high
strength bolt and Figure 3 shows the time required for sinking a square washer into a wood workpiece.
(2) Loosening time comparison (high strength bolts)
Figure 2 shows the time comparison when loosening an M16 bolt that was statically tightened at 200 N•m
{2040 kgf•cm, 1770 in-lbs.} with a torque wrench. The Model WR 12DM can loosen an M16 bolt in a half time
of the previous Model WR 12DH. In addition, the Model WR 12DM can loosen bolts that cannot be loosened
by the previous Model WR 12DH. It is very convenient for loosening bolts that secure molding boxes.
Tightening torque
--- 12 ---
0
4
3
2
1
5
6
7
WR 12DM
7.4
WR 12DH
C
9
8
4.6
8.1
Fig. 2
Fig. 3
0
4
3
2
1
5
6
7
WR 12DM
8.1
WR 12DH
C
9
8
3.2
8.3
*The data above are intended for reference purposes only because actual loosening torque will vary
depending on tightening conditions.
Tightening time (sec.)
Loosening time (sec.)
(3) Sinking time comparison (square washers)
Figure 3 shows the time required for tightening an M12 bolt into a pine laminated lumber of 105 mm square
until the square washers at both sides are sunk into the lumber by 1.3 mm respectively. The Model WR 12DM
can tighten strap bolts and corner bracings (used in Japanese wooden buildings) speedily as it can sink
washers into a workpiece quickly.
*The data above are intended for reference purposes only because actual time required for sinking
washers will vary depending on tightening conditions.
The 30% higher power motor and the 35% larger hammer are the main factors that increase the tightening
torque of the Model WR 12DM substantially. Comparison of hammer and number of strokes are shown below.
--- 13 ---
(4) Comparison of hammer and number of strokes
Thanks to the larger hammer (higher hammer inertia J) than the previous model, the number of strokes (N) of
the Model WR 12DM is increased. As a guide, stroking force is proportional for J X N2. Therefore, when the
J X N2 of the Model WR 12DH is 100, the J X N2 of the Model WR 12DM is about 1.5 times larger than the
Model WR 12DH as shown in the table below.
WR 12DM CWR 12DH
Model Unit
V
Outside diameter of hammer (D)
mm
Height of hammer (H)
mm
Voltage
kgmm
2
%
WH 12DM
12
42.6
20
37.4
3140
WR 12DM
12
39.5
21
28.8
2900
C
12
42
16.5
31.7
3070
120100
150
Hammer inertia J
Number of strokes (N)
J x N
2
min
-1
(No. of strokes/min.)
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