Hitachi Koki WH 12DM2 Instrucciones De Manejo página 15

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 socketis 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
kgf·cm N·m
M10 × 30
1000 100
High tension bolt
800
80
600 60
400 40
Ordinary bolt
200 20
0 0
0 1
Tightening time: sec
(Steel plate thickness
t = 10 mm)
kgf·cm N·m
M10 × 30
2000
200
1500 150
High tension
bolt
1000 100
500 50
Ordinary bolt
0 0
0 1
Tightening time: sec
(Steel plate thickness
t = 10 mm)
kgf·cm
1400
1200
1000
800
600
400
200
0
2 3
Tightening time: sec
(Steel plate thickness
t = 25 mm)
kgf·cm
2000
1500
1000
500
0
2 3
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.
N·m
M12 × 45
140
High tension bolt
120
100
80
60
Ordinary bolt
40
20
0
0 1 2 3
Fig. 22
N·m
M12 × 45
200
High tension
bolt
150
100
50
Ordinary bolt
0
0 1 2 3
Tightening time: sec
(Steel plate thickness
t = 25 mm)
Fig. 23
English
kgf·cm N·m
M14 × 50
1400 140
High tension bolt
1200 120
1000 100
800
80
Ordinary bolt
600 60
400 40
200 20
0 0
0 1 2
Tightening time: sec
(Steel plate thickness
t = 25 mm)
kgf·cm N·m
M14 × 50
2000 200
High tension
bolt
1500 150
1000 100
500 50
Ordinary bolt
0 0
0 1 2
Tightening time: sec
(Steel plate thickness
t = 25 mm)
3
3
14