60
English
1400
1200
1000
800
600
400
200
0
140
120
100
80
60
40
20
0
M14
×
50
0
1
2
3
kgf·cm
N·m
1400
1200
1000
800
600
400
200
0
140
120
100
80
60
40
20
0
M12
×
45
0
1
2
3
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. 22
Ordinary bolt
High tension bolt
Ordinary bolt
High tension bolt
<WH12DM2>
screw. Always keep the unit and the screw being
tightened in a straight line.
4. Use a tightening time suitable for the screw
The appropriate torque for a screw differs according
to the material and size of the screw, and the material
being screwed etc., so please use a tightening time
suitable for the screw. In particular, if a long tightening
time is used in the case of screws smaller than M8,
there is a danger of the screw breaking, so please
confirm the tightening time and the tightening torque
beforehand.
5. Work at a tightening torque suitable for the bolt
under impact
The optimum tightening torque for nuts or bolts differs
with material and size of the nuts or bolts. An
excessively large tightening torque for a small bolt
may stretch or break the bolt. The tightening torque
increases in proportion to the operation time. Use
the correct operating time for the bolt.
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. 22
and
23
)
(3) Diameter of bolt
The tightening torque differs with the diameter of the
bolt as shown in
Fig. 22
and
23
. 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.
(5) Using optional parts (WR12DM2)
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)
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
and
2
.
(7) Tightening torque varies, depending on the battery’s
charge level (WR12DM2)
Fig. 25
shows an example of the relationship between
tightening torque and the number of tightenings, for
WR12DM2. 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.
1000
800
600
400
200
0
0
1
2
3
100
80
60
40
20
0
M10
×
30
kgf·cm
N·m
Ordinary bolt
High tension bolt
