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4. 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.
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 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.
(3) Diameter of bolt
The tightening torque differs with the diameter of
the bolt. 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 (WR18DSDL)
The tightening torque is reduced a little when an
extension bar, universal joint or a long socket is used.
(6) Clearance of the socket (WR18DSDL)
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.
(7) Tightening torque varies, depending on the battery's
charge level.
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