Hitachi DH 40MR User manual

POWER TOOLS
TECHNICAL DATA
AND
SERVICE MANUAL
ROTARY HAMMER
DH 40MR
SPECIFICATIONS AND PARTS ARE SUBJECT TO CHANGE FOR IMPROVEMENT
LIST No. E467 Sep. 2002
D
MODEL
DH 40MR

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:
Symbols Utilized Competitors
Company Name Model Name
BOSCH GBH5-40DE
B
HILTI TE55
D
MAKITA HR4000C
C

Page
CONTENTS
1. PRODUCT NAME...........................................................................................................................1
2. MARKETING OBJECTIVE .............................................................................................................1
3. APPLICATIONS..............................................................................................................................1
4. SELLING POINTS ..........................................................................................................................1
4-1. Selling Point Descriptions .............................................................................................................. 2
5. SPECIFICATIONS ..........................................................................................................................3
5-1. Specifications................................................................................................................................. 3
5-2. Optional Accessories ..................................................................................................................... 4
6. COMPARISONS WITH SIMILAR PRODUCTS ..............................................................................8
6-1. Specification Comparisons ............................................................................................................ 8
6-2. Drilling Speed Comparisons .......................................................................................................... 9
6-3. Chiseling Performance Comparison ............................................................................................ 10
6-4. Comparison of Drilling Speed Change by Pushing Force ........................................................... 10
6-5. Drilling Speed and Quantity of Body Jumping ..............................................................................11
7. PRECAUTIONS IN SALES PROMOTION ...................................................................................11
7-1. Handling Instructions ....................................................................................................................11
7-2. Caution Plate ............................................................................................................................... 12
8. REFERENCE INFORMATION ......................................................................................................12
8-1. Grease Replacement................................................................................................................... 12
8-2. O-Ring Replacement ................................................................................................................... 12
8-3. Structure of DH 40MR Rotary Hammer ....................................................................................... 13
9. REPAIR GUIDE ............................................................................................................................18
9-1. Disassembly ................................................................................................................................ 18
9-2. Reassembly ................................................................................................................................. 20
9-3. Screw Locking Agent TB1401...................................................................................................... 23
9-4. Tightening Torque ........................................................................................................................ 23
9-5. Internal Wiring.............................................................................................................................. 24
9-6. Insulation Tests ............................................................................................................................ 25
9-7. No-load Current Value ................................................................................................................. 25
10. STANDARD REPAIR TIME (UNIT) SCHEDULES .....................................................................26
Assembly Diagram for DH 40MR

--- 1 ---
1. PRODUCT NAME
Hitachi Rotary Hammer, Model DH 40MR
2. MARKETING OBJECTIVE
The Model DH 40MR is an upgraded version of the current Models DH 40MA and DH 40MB, which feature the
use of SDS-max shank tools. The performance, durability and operability are greatly improved. With this
competitive Model DH 40MR, we aim to enhance the share of SDS-max type rotary hammers.
The main specifications are as follows:
(1) High drilling speed with low vibration and noise level
(2) Self-drilling (Good feeling)
(3) Internal double-insulation construction with sturdy aluminum frame
(4) Constant speed with variable speed control
(5) Soft-touch grip for easier handling
(6) Variabel lock mechanism for easy working-angle adjustment of chisels etc.
(7) Avery original design
3. APPLICATIONS
Drilling holes in concrete and drilling anchor holes
Demolishing and chiseling of concrete. Edging, gravel road digging, compacting and tamping, grooving,
cutting, stripping and roughing, etc.
[Application examples]
Air conditioning Piping and wiring Electric fixtures
Sanitary facilities Interior finishing Other building, construction and repair work
4. SELLING POINTS
Needle-pin type slip clutch
Internal double-insulation construction
with sturdy aluminum frame Constant speed with
variable speed control
Soft-touch grip handle
for easier handling
Soft-touch grip side-handle
for easier handling
High drilling speed with low vibration and noise level
Self-drilling (Good feeling)
A very original design
Change lever for switching between "Rotation +
Hammering" (for drilling), "Neutral" (for positioning
the tool tip) and "Hammering only" (for chiseling
and chipping)

--- 2 ---
4-1. Selling Point Descriptions
4-1-1. High drilling speed with low vibration and noise level
The drilling speed is 10 % faster than that of similar products thanks to efficient striking energy transmission and
speed setting. Even so, the Model DH 40MR produces lower vibration and noise levels than those of similar
products.
Maker •Model
Ratio of drilling speed %
Full-load vibration level dB (VL)
m/s2
HITACHI
DH 40MR
100
116.8
4-1-2. Self-drilling (Good feeling)
Thanks to the computer-simulated optimum striking characteristics, the quantity of body jumping is less than that
of the current Model DH 40MA and the working tool smoothly penetrates into the workpiece with a light pressing
force. The Model DH 40MR realizes quicker self-drilling with better impact feeling.
4-1-4. Dial type, constant speed with variable speed control
The Model DH 40MR is equipped with a built-in electronic control circuit
that can adjust the number of hammering steplessly between 1320 and
2650 min-1 with the dial. Even though the load varies, the Model
DH 40MR provides better operability and stable and efficient drilling
performance because the constant speed control minimizes changes in
number of rotation and hammering.
Impact efficiency
Maximum compressed air force (piston force)
Quantity of body jumping
About 10 % up
About 50 % down
About 25 % down
Full-load noise level dB (A)
No-load noise level dB (A)
6.9
92.4
79.5
HITACHI
DH 40MA/MB
64
118.0
7.9
94.6
89.4
B
85
119.8
9.8
93.7
85.0
D
64
116.1
6.4
93.2
83.0
C
74
118.5
8.4
93.5
80.3
* Ratio of drilling speed: A28-mm dia. drill bit is used.
Full-load vibration and noise levels: A 20-mm dia. drill bit is used.
4-1-3. Internal double-insulation construction with sturdy aluminum frame
The aluminum die-cast outer frame is very sturdy (same as the Models H 45MR/H 45SR). In addition, a plastic
internal S holder is adopted to realize double-insulation construction. Thus the housing has greater rigidity and
the double-insulated motor has greater durability. The Model DH 40MR is heavy-duty and the service life of the
carbon brush is greatly prolonged (1.5 times longer than the conventional one) minimizing disconnection of the
armature, deviation of the core and grease leakage.
4-1-5. Soft-touch grip for easier handling
The double-layer molded handle consists of a nylon resin base covered with a soft plastic layer to ensure a soft
touch and firm, non-slip grip of the handles.
Speed-adjust dial

--- 3 ---
5. SPECIFICATIONS
5-1. Specifications
Capacity
Power source
Current
Power input
Switch
Type of handles
Impact rate
Weight
Packaging
Standard accessories
Drill bit (Max. diameter): 40 mm (1-9/16")
Core bit (Max. diameter): 105 mm (4-1/8")
AC single phase 50 Hz or 60 Hz
950 W
Trigger switch
D-shaped handle and side handle
No load and full load: 1,320 to 2,650 min-1
Product: 6.5 kg (14.3 lbs.); excluding cord and side handle
Packed: 10.0 kg (22.1 lbs.)
Corrugated cardboard box with plastic tool case
•Plastic case ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1
•Side handle •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1
•Hex. bar wrench (for M6) •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1
•Hex. bar wrench (for M5) •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1
•Hex. bar wrench (for M4) •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1
•Stopper ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1
•Grease (A) •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1
4-1-6. Change lever for switching between "Rotaion + Hammering", "Neutral" and "Hammering only"
The Model DH 40MR provides three functions, "rotation + hammering"
function (for drilling), "neutral" function (for positioning the tool tip) and
"hammering only" function (for chiseling and chipping).
These function modes can be easily switched by using the change lever.
The tool angle can be easily changed in 12 steps by turning the grip
with the change lever positioned at "Neutral".
4-1-7. Needle-pin type slip clutch
The Model DH 40MR is equipped with a needle-pin type slip clutch for higher slip torque accuracy and enhanced
safety (same as the Model DH 40MA).
Voltage 110 V
10 A
120 V
9.2 A 220 V
5 A 230 V 4.8 A 240 V 4.6 A
Enclosure
Motor type AC single-phase series commutator motor
Materials: Aluminum alloy die casting
Nylon resin (Handle, handle cover, tail cover and crank cover)
Paint : Silver green metallic, black
Double insulation
Insulation structure
Rotation rate No load and full load: 240 to 480 min-1

--- 4 ---
5-2. Optional Accessories
1. Drilling work for through-holes (Rotation + Hammering)
+
+
(1) Drill bit (taper shank) (2) Taper shank adapter
(SDS max shank)
(3) Cotter
(1) Drill bit (SDS max shank)
Outer diameter
(mm)
16 (5/8")
19 (3/4")
22 (7/8")
25 (1")
28 (1-1/8")
32 (1-1/4")
38 (1-1/2")
40 (1-9/16")
Over length
(mm)
340 (13-3/8")
340 (13-3/8")
320 (12-5/8")
320 (12-5/8")
370 (14-9/16")
370 (14-9/16")
370 (14-9/16")
370 (14-9/16")
Code No.
313448
313449
313450
313451
313452
313453
313454
313455
Outer diameter
(mm)
16 (5/8")
19 (3/4")
22 (7/8")
25 (1")
28 (1-1/8")
32 (1-1/4")
38 (1-1/2")
40 (1-9/16")
Over length
(mm)
540 (21-1/4")
540 (21-1/4")
520 (20-15/32")
520 (20-15/32")
570 (22-7/16")
570 (22-7/16")
570 (22-7/16")
570 (22-7/16")
Code No.
313456
313457
313458
313459
313460
313461
313462
313463
2. Drilling work for anchor holes (Rotation + Hammering)
1 Drill bit (Taper shank)
+
(1) Drill bit (Taper shank)
Outer diameter (mm)
11 (7/16")
12.3 (15/32")
12.7 (1/2")
14.3 (9/16")
14.5 (9/16")
17.5 (11/16")
Code No.
944460
944461
993038
944462
944500
944463
(2) Taper shank adapter
Taper dimension Code No.
Morse taper No. 1 313464
(3) Cotter
Code No.
944477
2 SDS-plus shank bit adapter
+
(1) Drill bit (SDS-plus shank) (2) SDS-plus shank
bit adapter
(SDS max shank)
Code No. 313465
+

--- 5 ---
3. Boring work for large-diameter holes (Rotation + Hammering)
(1) Guide plate
(2) Center pin
(3) Core bit (4) Core bit shank
(SDS max shank)
+
++
(1) Guide plate
Core bits with outer diameter of 32, 35, 38, 45, 50, 54, 60, 64, 70, 75, 79, 94, 100, 105 mm (1-1/4", 1-3/8",
1-1/2", 1-3/4", 2", 2-1/8", 2-3/8", 2-2/1", 2-3/4", 2-15/16", 3-1/8", 3-1/16", 3-15/16", 4-1/8")
[Guide plate is not used with core bits with outer diameter of 25 mm (1") and 29 mm (1-1/8")]
(2) Center pin
Code No. 956009 for core bits with outer diameter of 32, 35 mm (1-1/4", 1-3/8")
Code No. 955165 for core bits with outer diameter of 38, 45, 50, 54, 60, 64, 70, 75, 79, 94, 100, 105 mm
(1-1/2", 1-3/4", 2", 2-1/8", 2-3/8", 2-1/2", 2-3/4", 2-15/16", 3-1/8", 3-11/16", 3-15/16", 4-1/8")
[Center pin is not used with core bits with outer diameter of 25 mm (1") and 29 mm (1-1/8").]
(3) Core bit
Outer diameter (mm)
25 (1")
29 (1-1/8")
32 (1-1/4")
35 (1-3/8")
38 (1-1/2")
45 (1-3/4")
Code No.
955994
955995
955996
955998
956000
955154
Outer diameter (mm)
50 (2")
54 (2-1/8")
60 (2-3/8")
64 (2-1/2")
70 (2-3/4")
75 (2-15/16")
Code No.
959706
955155
959707
956002
959708
959709
Outer diameter (mm)
79 (3-1/8")
94 (3-11/16")
100 (3-15/16")
105 (4-1/8")
Code No.
955157
956004
959710
955159
4. Hole drilling .................................... For drilling steel and wood
+
(1) 13 mm drill chuck
(13VLA)
+
(2) Chuck adapter
(SDS max shank)
(3) Chuck wrench
+
(1) 13 mm drill chuck (13VLA) (2) Chuck adapter (3) Chuck wrench
Code No. 950272 Code No. 313468 Code No. 930515
(4) Core bit shank (SDS max shank)
Code No. 313466 for core bits with outer diameter of 25, 29, 32, 35 mm (1", 1-1/8", 1-1/4", 1-3/8")
Code No. 313467 for core bits with outer diameter of 38, 45, 50, 54, 60, 64, 70, 75, 79, 94, 100, 105 mm
(1-1/2", 1-3/4", 2", 2-1/8", 2-3/8", 2-1/2", 2-3/4", 2-15/16", 3-1/8", 3-11/16", 3-15/16", 4-1/8")

--- 6 ---
(Socket) (1) Chemical anchor adapter
(SDS max shank)
+
+
(1) Bull point (SDS max shank)
12.7 mm (1/2")
19.0 mm (3/4")
Socket square size Code No.
313469
313470
5. Chemical anchor holes drilling work (Rotation + Hammering)
+
6. Demolition work (Hammering)
280 mm (11")
400 mm (15-3/4")
Overall length Code No.
313471
313472
7. Grooving and edging (Hammering)
+
(1) Cold chisel (SDS max shank)
280 mm (11")
400 mm (15-3/4")
Overall length Code No.
313473
313474
+
(1) Cutter (SDS max shank)
400 mm (15-3/4")
Overall length Width
50 mm (2")
8. Cutting and stripping (Asphalt cutting etc.) (Hammering)
Code No.
313475
9. Digging (Substitute pick-ax) (Hammering)
+
(1) Scoop (SDS max shank)
400 mm (15-3/4")
Overall length Code No.
313476

--- 7 ---
10. Surface roughing work (Hammering)
+
(1) Bushing tool
+
(2) Shank (SDS max shank)
220 mm (8-21/32")
Overall length Code No.
313479
313477
Code No.
11. Tamping work (Hammering)
+
(1) Rammer
+
(2) Shank (SDS max shank)
220 mm (8-21/32")
Overall length Code No.
313479
313478
150 mm x 150 mm
Code No.
500 g (1.1 lbs.) Can
12. Syringe (for chip removal)
Code No. 944575
Code No. 980927
70 g (2.5 oz) Tube
Code No. 308471
30 g (1 oz) Tube
Code No. 981840
13. Impact drill grease
(Note)
Code numbers listed above are subject to change without noitce. Please refer to periodic Technical News
Bulletins.

--- 8 ---
6. COMPARISONS WITH SIMILAR PRODUCTS
6-1. Specification Comparisons
Maker •Model
Item
Capacity
Drill bit dia. (mm)
Core bit dia. (mm)
(W)
(J)
(min-1)
(dB(VL))
Power input
Impact energy per stroke
Full-load rotation rate
Full-load impact rate
Full-load vibration level
No-load noise level
Full-load noise level
Dimensions
Insulation structure
Length
Height
Width
(mm)
(kg)
* Weight does not include cord and side handle.
(min-1)
(dB(A))
(dB(A))
(mm)
(mm)
Weight *
2,800/
1,400 --- 2,800
Hitachi
DH 40MR
360/
180 --- 360
Hitachi
DH 40MA/MB
40
(1-9/16")
950
8
105
(4-1/8")
118.0
94.6
87.9
444
(17-1/2")
252
(9-15/16")
103
(4-1/16")
6.5/6.6
(14.3/14.6 lbs.)
Double
insulation
40
(1-9/16")
950
10
240 --- 480
1,320 --- 2,650
105
(4-1/8")
116.8
92.4
79.5
435
(17-1/8")
255
(10-3/64")
104
(4-7/64")
6.5
(14.3 lbs.)
Double
insulation
40
(1-9/16")
1,100
8.5
0 --- 340
0 --- 3,300
105
(4-1/8")
119.8
93.7
85.0
450
(17-23/32")
255
(10-3/64")
102
(4-1/64")
6.2
(13.7 lbs.)
Double
insulation
B
32
(1-1/4")
900
7
0 --- 480
0 --- 2,630
90
(3-17/32")
116.1
93.2
83.0
440
(17-11/32")
230
(9-1/16")
90
(3-17/32")
5.9
(13.0 lbs.)
Double
insulation
D
40
(1-9/16")
900
7
230 --- 450
1,250 --- 2,500
105
(4-1/8")
118.5
93.5
80.3
455
(17-15/16")
250
(9-27/32")
104
(4-1/8")
6.2
(13.7 lbs.)
Double
insulation
C

--- 9 ---
6-2. Drilling Speed Comparisons
Drilling speed varies considerably depending on the work conditions. Use the factory test results shown in Fig. 1
for comparison purposes only.
Fig. 1
* Note that the data marked with asterisks are test results using drill bits which are beyond the tool's rated
capacity. Use the above data as a reference, for comparisons only.
[Test conditions]
Direction : Downward drilling
Pushing force : 98 N (10 kgf)
Test material : Concrete panel with a compression strength of 2,919 N/cm2(240 kgf/cm2)

--- 10 ---
6-3. Chiseling Performance Comparison
Chiseling performance varies considerably depending on the work conditions. Use the factory test results shown
in Fig. 2 for comparison purposes only.
Fig. 2
(Note) B's chiseling amount is greater than the others because the circuit is controlled to make the number of
hammering in the "Hammering only" mode higher than that in the "Rotation + Hammering" mode.
However, B has inconveniences such as unbalanced hammering, heavy vibration, heavy tool shake,
and difficulty in positioning the tool because B increases only the number of hammering without
changing the weight of the striker (that is, hammering energy). The Model DH 40MR realizes self-
chiseling in addition to self-drilling (4-1-2. Self-drilling (Good feeling)).
6-4. Comparison of Drilling Speed Change by Pushing Force
The graph shown in Fig. 3 illustrates the relationship between handle pushing force and drilling speed.
DH 40MR: Tool shake is not heavy in whole range. Good feeling.
DH 40MA/DH 40 MB: Tool shakes heavily at pushing force 50 N.
B: Tool shakes heavily at pushing force 50 N and 75 N.
D: Tool shake is not heavy in whole range, but the drilling
speed is slow and the feeling is not good.
Pushing force (N)
Fig. 3
Pushing force
Drilling speed (mm/min.)

--- 11 ---
6-5. Drilling Speed and Quantity of Body Jumping
The graph shown in Fig. 4 illustrates the relationship between
drilling speed and quantity of body jumping. The quantity of
body jumping is less than the similar products and the working
tool quickly penetrates into the workpiece.
Body jumping
is low !!
Quantity of body jumping is
low and the tool smoothly
penetrates into the
workpiece with good feeling.
Working tool quickly
penetrates into the
workpiece !!
Tool shake is low.
Fast
Pushing force: 100 N
Fig. 4
Ratio of quantity of
body jumping
Ratio of
drilling speed
Self drilling !!

--- 12 ---
7. PRECAUTIONS IN SALES PROMOTION
In the interest of promoting the safest and most efficient use of the Model DH 40MR Rotary Hammer by all of our
customers, it is very important that at the time of sale the salesperson carefully ensures that the buyer seriously
recognizes the importance of the contents of the Handling Instructions, and fully understands the meaning of the
precautions listed on the Caution Plate attached to each tool.
7-1. Handling Instructions
Although every effort is made in each step of design, manufacture and inspection to provide protection against
safety hazards, the dangers inherent in the use of any electric power tool cannot be completely eliminated.
Accordingly, general precautions and suggestions for the use of electric power tools, and specific precautions and
suggestions for the use of the Rotary Hammer are listed in the Handling Instructions to enhance the safe, efficient
use of the tool by the customer. Salespersons must be thoroughly familiar with the contents of the Handling
Instructions to be able to offer appropriate guidance to the customer during sales promotion.
7-2. Caution Plate
The Model DH 40MR unit is provided with a Caution Plate (illustrated below) which lists basic safety precautions
in use. Carefully ensure that the customer fully understands and follows these precautions before using tool.
For Australia and New Zealand
For the U.S.A. and Canada

--- 13 ---
8. REFERENCE INFORMATION
8-1. Grease Replacement
The striking portion and the speed reduction portion of the Model DH 40MR respectively use different types of
grease. It is not necessary to replenish the grease unless the tool is disassembled for repair or there is grease
leakage due to a damaged seal.
The striking portion uses special grease. To change the grease in the striking portion (inside the cylinder crank
case), carefully wipe the old grease off the parts, and re-lube with 50 g (1.8 oz) into the cylinder crank case
(connecting rod side). Take care not to overfill the grease as an excessive amount of grease can cause hammer
failure.
The speed reduction portion (inside the gear cover) uses Hitachi Motor Grease No. 29. The proper supply
volume is 30 g (1 oz). Never use the striking portion special grease in the speed reduction portion. Special
grease would leak into the motor portion and cause subsequent trouble.
Periodically replenish the inside of the slip clutch with Hitachi Motor Grease No. 29 to the full.
8-2. O-Ring Replacement
The O-rings (mounted on the striker and piston) are extremely important to ensure adequate sealing of the air
pressure. Although the O-rings are made of special rubber to give them a long service life, they do nonetheless
become worn, and should be replaced by new ones periodically depending on frequency of use of the tool. With
average use, it is recommended that the O-rings be replaced at least every six months to ensure maximum
effectiveness.
Retainer sleeve
Second
hammer
Grip
Front cap
Second
gear
Armature
Bevel pinion
Needle
holder
Control circuit ass'y
O-ring
Key rail
Crank shaft
Fig. 5
Needle roller
8-3. Structure of DH 40MR Rotary Hammer
Bevel gear
Piston First gear
Handle
Connecting rod
Needle pin
Striker
Cylinder Clutch
Air chamber

--- 14 ---
Torque transmission
Armature revolution is transmitted to the second gear to rotate the bevel gear via the slip mechanism between
the second gear and bevel pinion axes. Rotation of the bevel gear is then transmitted to the cylinder keyed
thereto through the clutch. Cylinder rotation is conveyed to the retainer sleeve coupled together by means of
four needle pins and, then to the drill bit inserted into the retainer sleeve by way of three key rails and two
needle rollers which couple them together.
Striking operation
The rotation of the armature is transferred to the crank shaft and connecting rod, which in turn cause the
piston to reciprocate inside the cylinder. As the piston reciprocates, the changing air pressure inside the air
chamber between the piston and the striker causes the striker to continuously strike against the end of the
second hammer. At the same time, the air-cushion effect within the air chamber absorbs the impact of the
striker. Should the air escape from the air chamber, the air-cushion effect would cease, and the impact energy
would not be absorbed. Accordingly, the O-rings mounted on the striker and piston play an extremely
important role in sealing the air within the air chamber.
Mechanism to prevent idle hammering
The arrangement against idle hammering of this rotary hammer is about the same as for the DH 40MA in
which, when the drill bit or bull point is not longer pressed against the concrete or similar material, the second
hammer moves to a position shown in Fig. 6 so that the striker is displaced from its hammering position. This
opens the air hole so that piston movement causes no change in air pressure chamber, thus stopping the
hammering action.
Second hammer
Second hammer, striker movements distance
Air chamber
Striker
Air hole
Fig. 6

--- 15 ---
Slip clutch mechanism
The slip clutch mechanism is described below with reference to Fig. 7. The bevel pinion and the gear holder
are coupled together by the key and press-fitting. Spring (C) and needle pins are housed in elongated
grooves of the gear holder. The needle pin is pressed against the inner face of second gear by spring (C) to
allow idle rotation of the second gear relative to the gear holder. When an excess torque is exerted on the
bevel pinion shaft, the needle pin is raised upon the projection of the second gear against the load of spring
(C) to allow idle rotation of the second gear. With the arrangement, the clutch slips when an excessive torque
is applied to the working tool as when the drill bit contacts steel bar/wire in the concrete, protecting the
operator from unexpected motion of the side handle.
Bevel pinion Needle pin
Bevel pinion
Gear holder
Gear holder Second gear
Key
Spring (C)
Gear holder groove
Fig. 7
Cross section A - A
The tool inlet is covered with the front cap
(made of rubber) to prevent chips from
entering inside. Two needle rollers fall into
the round groove of the drill bit to retain the
working tool, and three key rails transmit the
rotation torque. To attach a working tool, align
the groove positions turning the working tool,
then insert the working tool into the hole until
it contacts the innermost end of the hole.
Releasing the grip reverts the grip and
secures the tool in place. To remove the tool,
fully pull the grip backward and pull out the
tool (Fig. 8).
Tool holder
Tool
Front cap
Grip
Key rail (3 pieces)
Grip
Needle roller (2 pieces)
Fig. 8
Forward Backward

--- 16 ---
Handle and side handle
The handle section is of a two-layer structure. The base is made of glassfiber-reinforced plastic and the
outside layer is soft resin. They are molded in one piece.
The side handle also has a two-layer structure. The base is made of glassfiber-reinforced plastic base with a
steel nut and the outside layer is soft resin. They are molded in one piece. The newly designed handle and
side handle structure ensures more comfortable grip for improved operability.
Sealing and dust-proof structure
The cylinder crank case section is tightly sealed with three o-rings, three oil seals and rubber seal as shown in
Fig. 9. This prevents leakage of grease from the cases, while also protecting them against dust from outside.
The tool holder is also protected from foreign dust by means of a rubber front cap.
Rubber seal Oil seal
Front cap O-ring
Oil seal
Fig. 9
O-ring
Oil seal

--- 17 ---
Switching between "Rotation + Hammering", "Neutral" and "Hammering only"
All the shanks of the SDS-max type working tools such as drill
bits (for drilling) and bull points (for chiseling) have the same
shape. When chiseling or chipping with the Model DH 40MR,
it is necessary to stop the rotation and choose the
"Hammering only" mode by mean of the change lever to lock
the working tool against rotation.
Figure 10 is a cross-sectional view showing the "Rotation +
Hammering" mode, in which the bevel gear claw meshes with
the clutch claw to transmit rotation to the cylinder keyed to the
clutch, so as to rotate the working tool.
Figure 11 is a cross-sectional view showing the "Neutral"
mode, in which, with the change lever turned 90˚, the bevel
gear is brought out of engagement with the clutch to cut off
transmission of rotation. In this position, the tool holder grip
can be manually turned and the working tool (for chiseling or
chipping) is adjustable to the desired position in 12 steps
easily (Fig. 12).
Figure 13 is likewise a cross-sectional view showing the
"Hammering only" mode. With the change lever turned
another 90˚, the splines on the inner circumference of the lock
sleeve come into mesh with the splines on the outer
circumference of the clutch, so that the cylinder as well as the
working tool are prevented from rotating.
Although the Model DH 40MR has three selectable modes as
mentioned above, use of a working tool for chipping or
chiseling in the "Rotation + Hammering" mode will result in an
accident. Be sure to instruct the customers to select the
"Hammering only" mode when doing chiseling or chipping
work.
Fig. 10
Fig. 11
Fig. 13
Fig. 12
Clutch
Lock sleeve
Cylinder
Bevel gear
Change lever
Grip
Bevel gear
Change lever
Clutch
Cylinder
Lock sleeve
Change lever
Cylinder
Bevel gear
Lock sleeve Clutch