Hitachi WH 12DM2 Technical Data And Service Manual page 17

The 10% higher power motor and the larger hammer are the main factors that increase the tightening torque
of the Model WR 12DM2 substantially. Comparison of hammer and number of strokes is shown below.
(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 12DM2 is increased. When compared with C2, the hammer size is smaller but the number of
stokes is higher. Therefore the tightening torque is equivalent to C2. As a guide, striking force is proportional
for J X N 2 . Therefore, when the J X N
about 1.1 times larger than the Model WR 12DM and it is equivalent to or more than C2 as shown in the table
below.
WR 12DM2
Model
Voltage
Outside diameter of hammer (D)
Height of hammer (H)
Hammer inertia J
Number of strokes (N)
2
J x N
2 of the Model WR 12DM is 100, the J X N
WR 12DM
Unit WR 12DM2
V
12
mm
44
mm
18.6
2
kgmm
38.4
No. of
3240
strokes/min.
110
%
C1
WR 12DM C1
12
12
42
42.6
20 16.5
37.4 31.7
3140 3070
100 80
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2 of the Model WR 12DM2 is
P C2
P
12
44.2
18.6
39.7
3120
105
C2
14.4
42
22
42.3
2920
100