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Bolt
Nut
Fig. 18
Tightening torque varies, depending on the battery's charge level. Fig. 19 shows an
example of the relationship between tightening torque and the number of tightenings,
for a 3/8" (M10) high tensile bolt. As shown, tightening torque gradually weakens
with the increase in the number of tightenings. In particular, as the level 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
sharply. If this occurs, check torque level, then recharge the battery if necessary.
Kg – cm
(ft–lb)
800
(58)
600
(43)
400
(29)
200
(14)
0
Steel plate thickness t
3/8'' x 1-3/16'' (M10 x 30 mm) High tensile bolt (tightening time 1 sec)
When completely recharged
When completely discharged
0
50
Number of tightenings (PCS)/charging
(When using the EB9 type battery)
The following bolt is used.
Ordinary bolt: Hardness division 4.8
High tensile bolt: Hardness division
12.9
100
150
Fig. 19
a
200
250
23
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