Operation Manual

67
English
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1200
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0
140
120
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40
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0
M14 × 50
0 123
kgf·cm N·m
1400
1200
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0
140
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M12 × 45
0 123
kgf·cm N·m
Tightening torque
Tightening torque
Tightening torque
Tightening time: sec
(Steel plate thickness
t = 10 mm)
Tightening time: sec
(Steel plate thickness
t = 25 mm)
Tightening time: sec
(Steel plate thickness
t = 25 mm)
Fig. 23
Ordinary bolt
Hightension bolt
Ordinary bolt
Hightension bolt
<For WH12DM2>
6. Holding the tool
Hold the impact wrench firmly with both hands. In
this case hold the wrench in line with the bolt.
It is not necessary to push the wrench very hard.
Hold the wrench with a force just sufficient to
counteract the impact force.
7. Confirm the tightening torque
The following factors contribute to a reduction of the
tightening torque. So confirm the actual tightening
torque needed by screwing up some bolts before the
job with a hand torque wrench. Factors affecting the
tightening torque are as follows.
(1) Voltage
When the discharge margin is reached, voltage
decreases and tightening torque is lowered.
(2) Operating time
The tightening torque increases when the operating
time increases. But the tightening torque does not
increase above a certain value even if the tool is
driven for a long time. (See Fig. 23, 24, 25 and 26)
(3) Diameter of bolt
The tightening torque differs with the diameter of the
bolt as shown in Fig. 23, 24, 25 and 26. Generally a
larger diameter bolt requires larger tightening torque.
(4) Tightening conditions
The tightening torque differs according to the torque
ratio; class, and length of bolts even when bolts with
the same size threads are used. The tightening torque
also differs according to the condition of the surface
of workpiece through which the bolts are to be
tightened. When the bolt and nut turn together, torque
is greatly reduced.
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0 123
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M10 × 30
kgf·cm N·m
Ordinary bolt
Hightension bolt
(5) Using optional parts (WR12DM2, WR9DM2)
The tightening torque is reduced a little when an
extension bar, universal joint or a long socket is
used.
(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 1,
2, 3 and 4.
(7) Tightening torque varies, depending on the battery’s
charge level (WR12DM2, WR9DM2)
Fig. 28 and 29 shows an example of the relationship
between tightening torque and the number of
tightenings, for WR12DM2, WR9DM2. 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.