Hitachi WH 8DH Manual

POWER TOOLS
TECHNICAL DATA
AND
SERVICE MANUAL
CORDLESS IMPACT DRIVER
WH 8DH
CORDLESS IMPACT WRENCH
WR 8DH
SPECIFICATIONS AND PARTS ARE SUBJECT TO CHANGE FOR IMPROVEMENT
LIST Nos. WH 8DH: F832
WR 8DH: F833 Jul. 1999
W
MODEL
WH 8DH
WH 8DH WR 8DH
WR 8DH

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 6908DWA
WH 8DH

Page
CONTENTS
[ Business Section ]
1. PRODUCT NAME •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1
2. MARKETING OBJECTIVE ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1
3. APPLICATIONS ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1
4. SELLING POINTS •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 2
4-1. Selling Point Descriptions ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 4
5. SPECIFICATIONS •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 5
5-1. Specifications ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 5
5-2. Optional Accessories •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 6
6. COMPARISONS WITH SIMILAR PRODUCTS ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 10
6-1. Specification Comparisons (Cordless Impact Driver) ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 10
6-2. Specification Comparisons (Cordless Impact Wrench) •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 11
6-3. Tightening Torque ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 12
6-4 Tightening Speed ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 16
6-5. Number of Screws or Bolts Driven ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 17
7. PRECAUTIONS IN SALES PROMOTION •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 19
7-1. Safety Instructions •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 19
7-2. Tightening Torque Inspection Prior to Operation •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 21
7-3. Tightening Torque Variation ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 21
7-4. Suggestions and precautions for the Efficient Use of the Charger •••••••••••••••••••••••••••••••••••••••••••• 23
8. OTHER PRECAUTIONS •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 24
[ Service section ]
9. REPAIR GUIDE •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 25
9-1. Precautions in Disassembly and Reassembly ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 25
9-2. Precautions in Disassembly and Reassembly of Battery Charger ••••••••••••••••••••••••••••••••••••••••••••• 30
11. STANDARD REPAIR TIME (UNIT) SCHEDULES ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 31
[ Appendix ]
Assembly Diagram for WH 8DH ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 32
Assembly Diagram for WR 8DH •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 35

--- 1 ---
1. PRODUCT NAME
Hitachi Cordless Impact Driver, Model WH 8DH
Hitachi Cordless Impact Wrench, Model WR 8DH
2. MARKETING OBJECTIVE
The current Hitachi cordless impact driver series has provided excellent on-the-job performance thanks to their
design that produces no recoil force in tightening screws and bolts and also no damage to the screw heads.
The current DC 12V cordless impact driver Model WH 12DH and the cordless impact wrench Model WR 12DH
are well-reputed because they have better tightening performance and longer service life than previous models,
thanks to a replaceable carbon brush motor. Now, the new cordless impact driver Model WH 8DH is brought out
to respond to users' requests for a replaceable carbon brush motor for a DC 9.6 V product. The new cordless
impact wrench Model WR 8DH is also brought out. The Model WR 8DH has higher tightening torque than the
previous Model WH 8D2 and its square drive dimension is 12.7 mm (1/2") for use of commercially-available 1/2"
sockets. The construction of the Model WR 8DH is the same as that of the Model WH 8DH except the anvil (K)
assembly and the hammer case.
3. APPLICATIONS
•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, lag bolts, etc.
•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 signs, automobile repair, assembly of garages
and carports storage sheds, etc.
•Various other assembly, construction or repair facilities.

--- 2 ---
4. SELLING POINTS
(1) Cordless Impact Driver: WH 8DH
Faster screw fastening
Higher fastening torque
88.2 N•m (900 kgf•cm, 65 ft-lbs) Improved motor performance
•Replaceable carbon brushes for longer
motor life
•High-power fan-cooled DC magnet motor
•Higher heat-resistance
•The same torque and speed in both
forward and reverse modes
Longer service life
DC 9.6 V battery
EB 9B or EB 9H
Heavy-duty aluminum
hammer case
Variable speed switch
with electric brake
Easy-to-use forward/reverse
changeover pushing button
Ergonomically designed
handle for a comfortable grip
Grip inserts
front and rear

--- 3 ---
(2) Cordless Impact Wrench: WR 8DH
Higher fastening torque
98 N•m (1000 kgf•cm, 72 ft-lbs)
Improved motor performance
•Replaceable carbon brushes for longer
motor life
•High-power fan-cooled DC magnet motor
•Higher heat-resistance
•The same torque and speed in both
forward and reverse modes
Longer service life
DC 9.6 V battery
EB 9B or EB 9H
Heavy-duty aluminum
hammer case
Variable speed switch
with electric brake
Easy-to-use forward/reverse
changeover pushing button
Ergonomically designed
handle for a comfortable grip
[12.7 mm (1/2") Square drive]
Grip inserts
front and rear

--- 4 ---
4-1. Selling Point Descriptions
(1) Faster tightening speed
The Model WH 8DH provides faster driving speed than the previous model thanks to the high-power motor
and the higher moment of inertia of the hammer.
Tightening time comparison of the Model WH 8DH with the previous Model WH 8DA2 and maker C's model
are shown below. (Wood screw 4.2 mm dia. x 90 mm length, hemlock spruce)
HITACHI WH 8DH
HITACHI WH 8DA2
C
5.9 sec.
Model 510
sec.
6.5 sec.
6.8 sec.
(2) Improved motor performance
The Models WH 8DH and WR 8DH have high power thanks to the fan cooled DC magnet motor. They have
better heat-resistance because the built-in fan enhances cooling efficiency. Their motors have replaceable
carbon brushes, and the service life of the carbon brush has been extended by increasing its size by about 70
% (volume) compared to our previous model.
(3) Construction of replaceable carbon brushes
The carbon brush can be easily removed from the motor with a flat-blade screwdriver as shown in Fig. 2 and
can also be easily and securely mounted to the motor by hanging the claw of the carbon brush on the
connecting portion on the outside of the brush tube.
Claw of
carbon brush Collar of
carbon brush
Connecting portion at the
outside of brush tube
Fig. 1 Fig. 2 Fig. 3
(4) Safe handle shape
Compared with the previous WH 8DA2, the housing of the Model WH 8DH produces no clearance caused by
vibration because front and rear grip inserts [part names: grip (R) and grip (F), made of rubber] are provided at
the juncture of the handle, and the housing is secured with two screws at the center of the handle to prevent
the operator's hand from being pinched. Furthermore, the rear portion of the housing is shaped upward so not
to interfere with the base of the operator's thumb.

--- 5 ---
5. SPECIFICATIONS
5-1. Specifications
Model Cordless Impact Driver
WH 8DH
Capacity
Item Cordless Impact Wrench
WR 8DH
Small screw M4 --- M8 (5/32" --- 5/16")*1
Ordinary bolt M5 --- M12 (3/16" --- 15/32") Ordinary bolt M6 --- M14 (1/4" --- 9/16")
High-strength bolt M6 --- M10 (1/4" --- 3/8")
Tightening torque 88.2 N•m (900 kgf•cm, 65 ft-lbs)*2
98 N•m (1000 kgf•cm, 72 ft-lbs) *3
Tip condition 6.35 mm (1/4") Bit holder 12.7 mm (1/2") Square drive
Type of motor Fan cooled DC magnet motor
Enclosure Main body: Polyamide resin •••••• Housing
Aluminum alloy die casting •••••• Hammer case
Storage battery: ABS resign (black)
Charger: ABS resin (black)
Type of switch
Trigger switch with forward / reverse changeover pushing button (with brake and variable)
Handle configuration T-type
No-load rotational speed 0 --- 2,200 /min
Impact rate 0 --- 2,900 /min
Main body 1.6 kg (3.5 lbs) (Includes battery)*4
Battery 0.52 kg (1.1 lbs)
Overall length x height 176 mm (6-15/16") x 220 mm (8-21/32")
Center height 26 mm (1-1/64")
Battery (Type EB 9B) Sealed cylindrical nickel-cadmium batteries
Nominal voltage: DC 9.6V
Nominal life: Charging/discharging approximately 1,000 cycles (in case of Model
UC 14YF2)
Nominal capacity: 2.0 Ah
180 mm (7-1/8") x 220 mm (8-21/32")
Battery (Type EB 9H) Sealed cylindrical nickel-metal hydride batteries
Nominal voltage: DC 9.6V
Nominal life: Charging/discharging approximately 500 cycles (in case of Model
UC 14YF2)
Nominal capacity: 2.2 Ah
*1: In the case of tapping screws and wood screws, a minimum of M3 (1/8") is possible.
*2: This torque is based on tightening an M12 (15/32") bolt (strength grade: 12.9) for 3 seconds with a hexagonal socket.
*3: This torque is based on tightening an M12 (15/32") bolt (strength grade: 12.9) for 3 seconds with a hexagonal socket.
*4: Main body does not include accessory tools (hexagonal bit, etc.).
Charger (UC 14YF2) Charger power source: single-phase AC, 50/60 Hz
Voltage: Depending on the order specification
Power input: 44 W
Charging system: Constant current charge with full wave phase control
Overcharge protection system: (1) Battery voltage detection ( 2V system)
(2) Battery surface temperature detection
(thermostat or thermistor)
(3) 120 minute timer
Output voltage: 7.2 V --- 14.4 V
Output current: 1.9 A
Charging time: Approx. 60 minutes (for B-type storage battery at 20 ˚C)
Approx. 70 minutes (for H-type storage battery at 20 ˚C)
Product weight: 1.3 kg
Operable ambient temperature range: 0 ˚C --- 40 ˚C
The maximum allowable temperature of the EB 9B type battery is 60 ˚C and the
EB 9H type battery is 45 ˚C.
Weight

--- 6 ---
Prior to charging
During charging
Charging completed
Charging not
possible
High battery
temperature
Blinks
Lit
Blinks
Flickers
Lit
0.5 sec ON, 0.5 sec OFF
Stays ON constantly
0.5 sec ON, 0.5 sec OFF
0.1 sec ON, 0.1 sec OFF
Stays ON constantly
Pilot lamp indications (UC 14YF2)
Red pilot lamp
remains lit of flashes
Green pilot lamp is lit
Storage battery or charger
is faulty.
Charging not possible
because storage battery
temperature is too high.
5-2. Optional Accessories
(1) Optional accessories for the Model WH 8DH
•Plus driver bit
50 mm (2")
Bit No.
No. 2
No. 3
Code No.
992671
992672
•Hexagon socket
L
B
Stamped figures
9961778 (5/16")65 (2-9/16")8
Stamped figures
5 mm Hexagon socket
Part Name L
(mm) B (mm) Code No.
98532910 (3/8")65 (2-9/16")106 mm Hexagon socket
99617812 (15/32")65 (2-9/16")125/16" Hexagon socket 99617913 (1/2")65 (2-9/16")138 mm Hexagon socket
99618014 (9/16")65 (2-9/16")1410 mm Hexagon socket (small type)
99618116 (5/8")65 (2-9/16")1610 mm Hexagon socket 99618217 (21/32")65 (2-9/16")1710 mm Hexagon socket
99619721 (53/64")166 (6-17/32")211/2" Hexagon long socket
•Woodworking drill bit (Code No. 959183)
14 mm dia.
(35/64")
83 mm (3-17/64")

--- 7 ---
•Drill chuck adaptor set (Code No. 996195)
The drill chuck adaptor set permits mounting of various types of locally-available drill bits for a variety of drilling
operations.
(2) Optional accessories for the Model WR 8DH
•Each dimension and applicable bolt for each hexagon socket
Shape B Shape C Shape D
H
D
1
L1
L
D
1
L1L
D
1
L1
L
Sq
18
(23/32")
20
(25/32")
25
(1")
25
(1")
28
(1-3/32")
28
(1-3/32")
32
(1-1/4")
35
(1-3/8")
8
(5/16")
8
(5/16")
9
(11/32")
9
(11/32")
8
(5/16")
9
(11/32")
10
(3/8")
14
(9/16")
40
(1-9/16")
40
(1-9/16")
40
(1-9/16")
40
(1-9/16")
32
(1-1/4")
34
(1-11/32")
36
(1-13/32")
40
(1-9/16")
B
B
B
B
C
C
D
D
10
(3/8")
12
(15/32")
13
(1/2")
14
(9/16")
17
(21/32")
19
(23/32")
21
(53/64")
22
(7/8")
W 5/16"
W 3/8"
W 7/16"
W 1/2"
M 8
(5/16")
M 10
(3/8")
M 12
(15/32")
M 14
(9/16")
M 16
(5/8")
M 6
(1/4")
M 8
(5/16")
M 10
(3/8")
M 12
(15/32")
M 14
(9/16")
M 12
(15/32")
944291
873632
873539
873540
873536
873624
873626
873627
10 mm
12 mm
13 mm
14 mm
17 mm
19 mm
21 mm
22 mm
Hexagon
socket
12.7 mm
(1/2")
Square
drive
dimension
Sq
Part Name
Code No.
Nominal diameter of applicable bolts
Dihedral
width
H (mm) Shape
Socket primary dimensions
(mm)
ISO
(high-strength)
ISO
(ordinary)
ISO
(small type)
Inch
screw L L1D1
•Each dimension and applicable bolt for each long socket
Shape B Shape D
H
D
1
(dia.)
L1
L
L1
L
Sq
L2
D
1
(dia.)
L2

--- 8 ---
20
(25/32")
21.5
(53/64")
22
(7/8")
25
(1")
25
(1")
28
(1-3/32")
28
(1-3/32")
31
(1-7/32")
31
(1-7/32")
31
(1-7/32")
32.5
(1-9/32")
20
(25/32")
20
(25/32")
20
(25/32")
24
(15/16")
24
(15/16")
24
(15/16")
24
(15/16")
24
(15/16")
24
(15/16")
24
(15/16")
24
(15/16")
52
(2-3/64")
52
(2-3/64")
52
(2-3/64")
52
(2-3/64")
75
(2-15/16")
52
(2-3/64")
75
(2-15/16")
52
(2-3/64")
75
(2-15/16")
125
(2-15/16")
52
(2-3/64")
B
B
B
B
B
B
B
D
D
D
D
12
(15/32")
13
(1/2")
14
(9/16")
17
(21/32")
17
(21/32")
19
(23/32")
19
(23/32")
21
(53/64")
21
(53/64")
21
(53/64")
22
(7/8")
W 5/16"
W 3/8"
W 3/8"
W 7/16"
W 7/16"
W 1/2"
W 1/2"
W 1/2"
M 8
(5/16")
M 10
(3/8")
M 12
(15/32")
M 12
(15/32")
M 14
(9/16")
M 14
(9/16")
M 16
(5/8")
M 8
(5/16")
M 10
(3/8")
M 10
(3/8")
M 12
(15/32")
M 12
(15/32")
M 14
(9/16")
M 12
(15/32")
955138
955139
955140
955141
955149
955142
955150
955143
955151
991480
955144
12 mm
13 mm
14 mm
17 mm
17 mm
19 mm
19 mm
21 mm
21 mm
21 mm
22 mm
Long
socket
12.7 mm
(1/2")
Square
drive
dimension
Sq
Part Name Code
No.
Nominal diameter of applicable bolts
Dihedral
width
H (mm)
Shape
Socket primary dimensions (mm)
ISO
(high-strength)
ISO
(ordinary)
ISO
(small type)
Inch
screw LL1D1
•Bit adaptor (Code No. 991476)
6.35 mm (1/4") 45 mm (1-25/32")
13.5 mm dia.
(17/32")
12.7 mm (1/2")
34
(1-11/32")
34
(1-11/32")
34
(1-11/32")
34
(1-11/32")
57
(2-1/4")
34
(1-11/32")
57
(2-1/4")
34
(1-11/32")
57
(2-1/4")
107
(4-7/32")
34
(1-11/32")
L2
Part name Overall length
(mm) Code No.
Plus hd.
driver bit
No.2
Plus hds.
driver bit
No.3
45 (1-25/32") 955229
70 (2-3/4") 955654
45 (1-25/32") 955230
70 (2-3/4") 955655
•Extension bar [Overall length 100 mm (3-15/16") ] (Code No. 873633)
•Universal joint (Code No. 992610)
•Socket ass'y for duct •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• Dihedral width of
applicable bolts Code No.
993658
13 (1/2") 992613
14 (9/16") 992615
12 (15/32")
•EW-14R corner attachment (Code No. 9329-9001)

--- 9 ---
(3) Optional accessories for the Models WH 8DH and WR 8DH
•Holster (Code No. 307824)
Use the holster to hold the unit during its operation.
Carefully read the warnings attached to the holster for safe use.
•Hook (Code No. 308090)
Use the hook to hold the unit during its operation.
Carefully read the instructions that come with the hook to learn how to use it.

--- 10 ---
6. COMPARISONS WITH SIMILAR PRODUCTS
6-1. Specification Comparisons (Cordless Impact Driver)
M 4 --- M 8
(5/32" --- 5/16")
HITACHI
WH 8DH WH 8DA2 C
Maker
Model
Item M 5 --- M 8
(3/16" --- 5/16") M 4 --- M 8
(5/32" --- 5/16")
Catalog specifications
Capacity
Small screw
M 5 --- M 12
(3/16" --- 15/32") M 5 --- M 12 (3/16" --- 15/32") M 5 --- M 12 (3/16" --- 15/32")
Ordinary bolt
M 5 --- M 10
(3/16" --- 3/8") M 5 --- M 10 (3/16" --- 3/8") M 5 --- M 10 (3/16" --- 3/8")
High-strength bolt
88.2
(900 kgf•cm, 65 ft-lbs)*278.4 (800 kgf•cm, 58 ft-lbs)*378.4 (800 kgf•cm, 58 ft-lbs)*3
Max. tightening torque N•m
0 --- 2,200 2,200 0 --- 2,200No-load rotation speed /min
0 --- 2,900 2,800 0 --- 2,800Impact rate /min
1.6 (3.5 lbs) 1.4 (3.1 lbs) 1.4 (3.1 lbs)Main body weight kg
91.1
(930 kgf•cm, 67.3 ft-lbs)*283.8
(850 kgf•cm, 61 ft-lbs)*385.8 (875 kgf•cm, 63.3 ft-lbs)*3
Max. tightening torque N•m
Measured figures
0 --- 2,230 2,150 0 --- 2,470No-load rotation speed /min 0 --- 2,790 2,700 0 --- 2,680Impact rate /min
176 x 220
(6-15/16" x 8-21/32") 175 x 218
(6-7/8" x 8-19/32")
Overall length x height mm 171 x 232
(6-47/64" x 9-9/64")
26 (1-1/64") 26 (1-1/64") 26 (1-1/64")Center height mm 1.6 (3.5 lbs) 1.47 (3.2 lbs) 1.5 (3.3 lbs)Main body weight kg
67 66 68
No-load sound pressure level
dB(A) Driver chuck Driver chuck Driver chuck
Tool tip mounting system
Trigger switch with
forward / reverse
changeover pushing
button with brake and
variable
Type of switch Trigger switch with
forward / reverse
changeover pushing
button with brake
Variable speed switch with
forward/reverse
changeover lever
DC magnet DC magnet DC magnet
Type of motor
9.6 9.6 9.6
Voltage
20 20 20
Current
EB 9B or EB 9H EB 9 9122
Battery
V
A
Type EB 9B: 2.0
EB 9H: 2.2 1.3 2.0
Nominal capacity Ah
9.6 9.6 9.6
Nominal voltage V
0 --- 40 5 --- 40 ------
Ambient temperature
˚C
UC 14YF2 UC 12Y DC1411
Model
44 51 ------
Power input capacity
VA
7.2 --- 14.4 2.4 --- 12 7.2 --- 14.4
Recharging voltage
V•Plastic tool case
•Charger (UC 14YF2) •Plastic tool case
•Charger (UC 12Y) •Plastic tool case •Charger (DC1411)
Standard accessories
Charger
*1: In the case of tapping screws and wood screws, a minimum of M3 (1/8") is possible.
*2: Max. tightening torque is based on tightening an M12 (5/32") bolt (strength grade: 12.9) for 3 seconds with a hexagon
socket.
*3: Max. tightening torque is based on tightening an M10 (3/8") bolt (strength grade: 12.9) for 3 seconds with a hexagon socket.
*4: Main body weight does not include accessory tools (hexagon bit, etc.).
*1
*4
*2
*4

--- 11 ---
6-2. Specification Comparisons (Cordless Impact Wrench)
HITACHI
WR 8DH
Maker
Model
Item
Catalog specifications
Capacity
M 6 --- M 14
(1/4" --- 9/16")
Ordinary bolt
M 6 --- M 10
(1/4" --- 3/8")
High-strength bolt
98
(1,000 kgf•cm, 72 ft-lbs)
Max. tightening torque N•m
0 --- 2,200
No-load rotation speed /min 0 --- 2,900
Impact rate /min
1.6 (3.5 lbs)
Main body weight kg 100
(1,010 kgf•cm, 73.1 ft-lbs)
Max. tightening torque N•m
Measured figures
0 --- 2,230
No-load rotation speed /min
0 --- 2,790
Impact rate /min 180 x 220
(7-1/8" x 8-21/32")
Overall length x height mm
26 (1-1/64")
Center height mm
1.6 (3.5 lbs)
Main body weight kg 67
No-load sound pressure level
dB(A)
Pin/O-ring or plunger
Tool tip mounting system Trigger switch with forward/reverse
changeover pushing button with
brake and variable
Type of switch
DC magnet
Type of motor
9.6
Voltage
20
Current
EB 9B or EB 9H
Battery
V
A
Type EB 9B: 2.0
EB 9H: 2.2
Nominal capacity Ah
9.6
Nominal voltage V0 --- 40
Ambient temperature
˚C
UC 14YF2
Model
44
Power input capacity
VA 7.2 --- 14.4
Recharging voltage
V•Plastic tool case
•Charger (UC 14YF2)
Standard accessories
Charger
*1: Max. tightening torque is based on tightening an M12 (5/32") bolt (strength grade: 12.9) for 3 seconds with a hexagon
socket.
*2: Main body weight does not include accessory tools (hexagon bit, etc.).
*1
*2
*1
*2
WH 8D2
M 5 --- M 12
(3/16" --- 15/32")
M 5 --- M 10
(3/16" --- 3/8")
88.2
(900 kgf•cm, 65.1 ft-lbs)
2,200
2,800
1.4 (3.1 lbs)
93.1
(950 kgf•cm, 68.7 ft-lbs)
2,150
2,700
171 x 218
(6-23/32" x 8-19/32")
26 (1-1/64")
1.46 (3.2 lbs)
66
Pin/O-ring or plunger
Trigger switch with forward /
reverse changeover pushing button
with brake DC magnet
9.6
20
EB 9
1.2
9.6
5 --- 40
UC 12Y
51
2.4 --- 12
•Charger (UC 12Y)

--- 12 ---
6-3. Tightening Torque
6-3-1. Tightening Torque Characteristic Comparisons
The Model WH 8DH and WR 8DH provide greater tightening torque than the previous models thanks to the high
power motor and the higher moment of inertia of the hammer. The tightening torque does not drop even when
loosening bolts because the motor runs at the same torque and speed in both the forward and reverse directions.
Tightening torque comparisons of Models WH 8DH and WR 8DH with previous models are shown in Figs. 4-1 and
4-2. It should be noted that M12 (15/32") and M10 (3/8") strength grade 12.9 high-strength bolts were utilized in
the tests to ensure that the bolts were not stripped or distorted, even though such bolts are actually beyond the
recommended maximum capacity of these models. Accordingly, the data in the figures below are intended for
reference purposes only.
(1) Impact Driver
Fig. 4-1
Fig. 4-2
Test conditions
Bolt: M12 x 45 mm (15/32" x 1-3/4")
M10 x 30 (3/8" x 1-3/16")
(strength grade: 12.9)
Steel plate: Mild steel
M12 (15/32") Thickness = 25 mm (1")
M10 (3/8") Thickness = 10 mm (3/8")
Accessory tool: Hexagon socket ass'y
* An M10 x 30 high-strength bolts are tested unless
otherwise specified.
WH 8DH (M12 x 45)
WH 8DH*
WH 8DA2
200
(19.6 N
•
m,
14 ft-lbs)
0123
400
(39.2 N
•
m,
29 ft-lbs)
600
(58.8 N
•
m,
43 ft-lbs)
800
(78.4 N
•
m,
58 ft-lbs)
1000
(98 N
•
m,
72 ft-lbs)
(kgf
•
cm)
(sec.)
Tightening time
Tightening torque
C (forward)
[Tightening torque
in reverse rotation
is about 90 % of
that in forward
rotation.]
(2) Impact Wrench
WR 8DH
WH 8D2
200
(19.6 N•m,
14 ft-lbs)
0123
400
(39.2 N•m,
29 ft-lbs)
600
(58.8 N•m,
43 ft-lbs)
800
(78.4 N•m,
58 ft-lbs)
1000
(98 N•m,
72 ft-lbs)
(kgf
•
cm)
(sec.)
Tightening time
Tightening torque
Test conditions
Bolt: M12 x 45 mm (15/32" x 1-3/4")
(strength grade: 12.9)
Steel plate: Mild steel
M12 (15/32") Thickness = 25 mm (1")
Accessory tool: Hexagon socket ass'y

--- 13 ---
6-3-2. Screw Diameter and Appropriate Tightening Torque
Generally speaking, the appropriate tightening torque for a screw can be determined by the strength grade of the
screw and the material tightened. Tables 1 and 2, and Fig. 5 below list data relative to the strength grade of
various screws and the appropriate tightening torque. For further reference, appropriate tightening torque is
calculated with the following formula. Study and use this formula for accurate selection of tightening torque.
T=k•d•p
T: Appropriate tightening torque (kgf•cm)
k: Torque coefficient (0.17)
d: Nominal diameter for the screw (mm)
p: Recommended axial tightening force to be applied to the screw (kgf)
p=rated axial stress (kgf/cm2) x 0.8 x effective sectional area of the thread (mm2)
•Strength grade and rated axial stress of threads
Strength grade
Rated axial stress (kgf/mm2)
Material
Heat treatment
4.8 6.8 8.8 12.9
29.1 43.7 58.2 95
Mild steel Alloy steel including Ni, Mn, Cr, etc.
None Processed-hard material
•Diameter and effective sectional areas of threads
Kind of thread (x pitch)
Effective sectional area of
thread (mm2)
M5 x 0.8 mm
(3/16")
14.2
M6 x 1 mm
(1/4")
20.1
M8 x 1.25 mm
(5/16")
36.6
M10 x 1.5 mm
(3/18")
58.0
M12 x 1.75 mm
(15/32")
84.3
M14 x 2 mm
(9/16")
115
•Thread diameter and appropriate tightening torque
Fig. 5
Strength grade 12.9
(high-strength bolt)
Strength grade 8.8
(high-strength bolt)
Strength grade 6.8
(ordinary bolt)
Strength grade 4.8
(ordinary bolt)
0
05
(3/16")
6
(1/4")
8
(5/16")
10
(3/8")
12
(15/32")
14
(9/16")mm
200
(19.6 N
•
m, 14 ft-lbs)
400
(39.2 N
•
m, 29 ft-lbs)
600
(58.8 N
•
m, 43 ft-lbs)
800
(78.4 N
•
m, 58 ft-lbs)
1000
(98 N
•
m, 72 ft-lbs)
1200
(117.6 N
•
m, 86 ft-lbs)
(kgf•cm)
Thread diameter
Appropriate tightening torque
Table 1
Table 2

--- 14 ---
200
(19.6 N•m,14 ft-lbs)
0123
400
(39.2 N•m,29 ft-lbs)
600
(58.8 N•m,43 ft-lbs)
800
(78.4 N•m,58 ft-lbs)
1000
(98 N•m,72 ft-lbs)
(kgf•cm)
Tightening time
[steel plate thickness:
t=3/8" (10 mm)]
M8 x 30 mm
(5/16" x 1-3/6")
Tightening torque
High-strenge bolt
Ordinary bolt 200
(19.6 N•m,14 ft-lbs)
0123
400
(39.2 N•m,29 ft-lbs)
600
(58.8 N•m,43 ft-lbs)
800
(78.4 N•m,58 ft-lbs)
1000
(98 N•m,72 ft-lbs)
(kgf•cm)
Tightening time
[steel plate thickness:
t=3/8" (10 mm)]
M10 x 30 mm
(8/8" x 1-3/6")
Tightening torque
High-strenge bolt
Ordinary bolt
200
(19.6 N•m,14 ft-lbs)
0123
400
(39.2 N•m,29 ft-lbs)
600
(58.8 N•m,43 ft-lbs)
800
(78.4 N•m,58 ft-lbs)
1000
(98 N•m,72 ft-lbs)
1200
(117.6 N•m,86 ft-lbs)
(kgf•cm)
Tightening time
[steel plate thickness:
t=1" (25 mm)]
M12 x 45 mm
(15/32" x 1-3/4")
Tightening torque
High-strenge bolt
Ordinary bolt
(sec.)
(sec.)
(sec.)
6-3-3. Bolt Tightening Torque Characteristics
Figs. 6-1 and 6-2 show relationships between time and tightening torque for individual bolt types and sizes. While
the data are useful for handy reference, actual tightening torque will vary depending on tightening conditions and
other variables. For details, please refer to Para. 7-3, Tightening Torque Variation.
(Note)
•The term "tightening time" indicates the impact time after the lower surface of the bolt has come in contact with
the material into which it is being tightened.
•In the tightening conditions shown in Figs. 6-1 and 6-2, the screws are being tightened directly into a steel
plate; accordingly, the torque goes up very abruptly in comparison with ordinary bolt tightening conditions.
•Model WH 8DH
Fig. 6-1
Bolt
Nut
Steel plate
thickness: t
* The following bolts were utilized:
Ordinary bolt; strength grade 4.8
High-strength bolt; strengh grade
12.9
Strength grade is read as follows:
4.8
Yield point or durable force:
(45,500 psi)
Tensile strength of the bolt:
(56,900 psi)

--- 15 ---
200
(19.6 N
•
m,14 ft-lbs)
0123
400
(39.2 N
•
m,29 ft-lbs)
600
(58.8 N
•
m,43 ft-lbs)
800
(78.4 N
•
m,58 ft-lbs)
1000
(98 N
•
m,72 ft-lbs)
1200
(117.6 N
•
m,86 ft-lbs)
(kgf•cm)
Tightening time
[steel plate thickness:
t=3/8" (10 mm)]
M8 x 30 mm
(5/16" x 1-3/6")
Tightening torque
High-strenge bolt
Ordinary bolt
200
(19.6 N
•
m,14 ft-lbs)
0123
400
(39.2 N
•
m,29 ft-lbs)
600
(58.8 N
•
m,43 ft-lbs)
800
(78.4 N
•
m,58 ft-lbs)
1000
(98 N
•
m,72 ft-lbs)
1200
(117.6 N
•
m,86 ft-lbs)
(kgf•cm)
Tightening time
[steel plate thickness:
t=1" (25 mm)]
M12 x 45 mm
(15/32" x 1-3/4")
Tightening torque
High-strenge bolt
Ordinary bolt
200
(19.6 N
•
m,14 ft-lbs)
0123
400
(39.2 N
•
m,29 ft-lbs)
600
(58.8 N
•
m,43 ft-lbs)
800
(78.4 N
•
m,58 ft-lbs)
1000
(98 N
•
m,72 ft-lbs)
1200
(117.6 N
•
m,86 ft-lbs)
(kgf•cm)
Tightening time
[steel plate thickness:
t=3/8" (10 mm)]
M10 x 30 mm
(8/8" x 1-3/6")
Tightening torque
High-strenge bolt
Ordinary bolt
(sec.)
(sec.)
(sec.)
•Model WR 8DH
Fig. 6-2

--- 16 ---
6-4. Tightening Speed
Tightening speed comparisons of the Model WH 8DH with the previous Model WH 8DA2 and maker C's model
are shown below. The data shown below are intended for reference purposes only because actual tightening
speed will vary depending on the tightening conditions such as ambient temperature, charging capacity and
workpieces.
1 Tightening time (sec.) (Wood screw 4.2 mm dia. x 90 mm length, hemlock spruce)
HITACHI WH 8DH
HITACHI WH 8DA2
C
5.9 sec.
Model 510
sec.
6.5 sec.
6.8 sec.
HITACHI WH 8DH
HITACHI WH 8DA2
C
3.0 sec.
Model 1sec.
3.3 sec.
3.5 sec.
2345
HITACHI WH 8DH
HITACHI WH 8DA2
C
3.2 sec.
Model 1sec.
3.5 sec.
3.8 sec.
2345
HITACHI WH 8DH
HITACHI WH 8DA2
C
6.9 sec.
Model 510
sec.
8.5 sec.
8.7 sec.
2 Tightening time (sec.) (Wood screw 4.2 mm dia. x 75 mm length, soft wood)
3 Tightening time (sec.) (Wood screw 4.2 mm dia. x 90 mm length, soft wood)
4 Tightening time (sec.) (Wood screw 5.5 mm dia. x 120 mm length, soft wood)

--- 17 ---
5 Tightening time (sec.) (Teks screw 4 mm dia. x 13 mm length, SPCC 1.6 t )
6 Tightening time (sec.) (Wood screw 3.8 mm dia. x 20 mm length, lauan)
HITACHI WH 8DH
HITACHI WH 8DA2
C
2.5 sec.
Model 1sec.
3.0 sec.
3.0 sec.
2345
HITACHI WH 8DH
HITACHI WH 8DA2
C
1.2 sec.
Model 12
sec.
1.3 sec.
1.2 sec.
6-5. Number of Screws or Bolts Driven
6-5-1. Per-Charge Working Capacity Comparisons
Test data on the number of screws or bolts which can be driven per battery charge by the new models vs. the
previous models are shown in the tables below. Please note that the data below are intended for general
reference only as the number of screws which can be tightened per charge will vary slightly depending on screw
tightening conditions, screw sizes, ambient temperatures and the charging capacity of the battery.
(1) Number of screws or bolts driven (Cordless impact driver)
Battery
Tightening condition Model HITACHI
WH 8DH HITACHI WH 8DA2 C
EB 9B EB 9B 9122
(Corresponding EB 9B)
Wood screw 3.8 mm dia. x 20 mm
(soft wood) 430 460 450
Wood screw 4.0 mm dia. x 50 mm
(soft wood) 300 300 290
Wood screw 4.2 mm dia. x 75 mm
(soft wood) 220 220 210
Machine screw M8 x 16 mm 1,120 1,120 950
Teks screw 4.0 mm dia. x 13 mm
Mild steel plate t=1.6 170 170 160