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3. Work at a tightening torque suitable for the bolt under impact
The optimum tightening torque for nuts and bolts differs with material and size
of the nuts and bolts. An excessively large tightening torque for a small bolt may
stretch or break the bolt. The tightening torque increases proportionally to the
operating time. Use the correct operating time for the bolt.
4. Holding the tool
Hold the lmpact Wrench firmly with both hands by the body handle and the side
handle. 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.
5. 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 hand torque wernch. Factors affecting the tightening torque are as
follows.
(1) Voltage:
When the discharge margin is reached, voltage decreases and tightening torque
declines.
(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 Figs. 14, 15, 16 and 17)
(3) Diameter of bolt:
The tightening torque differs with the diameter of the bolt as shown in Figs. 14,
15, 16 and 17. Generally a larger diameter bolt has a 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 metal through which the
bolts are to be tightened.
(5) Using optional parts:
The tightening torque is reduced a little when an extension bar, universal joint
or a long socket is used.
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