Hitachi WR9DM2 - Manual (Page 23)

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23
(6) Clearance of the socket (WR12DM2, WR9DM2)
A worn or deformed hex. or a square-holed socket will not give an adequate tightness
to the fitting between the nut or anvil, consequently resulting in loss of tightening
torque.
Using an improper socket which does not match to the bolt will result in an insufficient
tightening torque. Matching socket and bolt sizes are shown in Table 4, 5, 6 and 7.
(7) Tightening torque varies, depending on the battery’s charge level (WR12DM2, WR9DM2)
Fig. 22 and 23 show an example of the relationship between tightening torque and the
number of tightenings. As shown, tightening torque gradually weakens with the increase
in the number of tightenings. In particular, as the torque decreases very close to the
complete discharge (“a” margin in graph), the unit’s impact weakens, the number of
time impacts declines and tightening torque drops off abruptly. If this occurs, check
torque level, then recharge the battery if necessary.
9/16"×1-15/16"
(M14×50)
0 1 2 3
kgf·cm
(in-lbs)
(1215)
(1042)
(868)
(694)
(521)
(347)
(174)
1400
1200
1000
800
600
400
200
0
N·m
140
120
100
80
60
40
20
0
15/32"×1-3/4"
(M12×45)
0 1 2 3
kgf·cm
(in-lbs)
N·m
(1215)
(1042)
(868)
(694)
(521)
(347)
(174)
140
120
100
80
60
40
20
0
1400
1200
1000
800
600
400
200
0
0 1 2 3
kgf·cm
(in-lbs)
1000
800
600
400
200
100
80
60
40
20
0
(868)
(695)
(521)
(347)
(174)
0
3/8"×1-5/32"
(M10×30)
N·m
Tightening torque
Tightening torque
Tightening torque
Tightening time: sec
(Steel plate thickness
t = 1" (25 mm))
Tightening time: sec
(Steel plate thickness
t = 1" (25 mm))
Tightening time: sec
(Steel plate thickness
t = 3/8" (10 mm))
Fig. 17
Ordinary bolt
High strength bolt
High strength bolt
Ordinary bolt
High strength bolt
Ordinary bolt