Hitachi WH 18DSDL Safety Instructions And Instruction Manual page 16

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4. Work at a tighteningtorque suitable for the bolt
under impact
The optimum tightening torque for nuts or bolts
differs with materialand sizeof the nuts or bolts.
An excessively large tightening torque for a small
bolt may stretch or break the bolt. The tightening
torque increasesin proportion to the operationtime.
Usethe correct operatingtime for the bolt.
5. Confirm the tightening torque
The following factors contribute to a reduction of
the tightening torque. So confirm the actual
tighteningtorque neededby screwingup somebolts
before the job with a hand torque wrench. Factors
affectingthe tightening torque areas follows.
(1) Voltage
When the discharge margin is reached, voltage
decreasesandtightening torque is lowered.
(2) Operating time
Thetightening torque increaseswhen the operating
time increases.But the tightening torque does not
increaseabove a certain value even if the tool is
driven for a long time.
(3) Diameterof bolt
The tightening torque differs with the diameter of
the bolt. Generally a larger diameter bolt requires
larger tightening torque.
(4) Tightening conditions
Thetighteningtorque differs accordingto the torque
ratio, class,andlength of boltsevenwhen bolts with
the same size threads are used. The tightening
torque also differs accordingto the condition of the
surfaceof workpiecethrough which the bolts areto
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
extensionbar,universal j oint or a long socketis used.
(6) Clearanceof the socket (WR18DSDL)
A worn or deformed hex. or a square-holedsocket
will not give an adequate tightness to the fitting
betweenthe nut or anvil, consequently resulting in
lossof tightening torque.
Using an improper socketwhich doesnot match to
the bolt will result in an insufficient tightening
torque.
(7) Tighteningtorque varies,dependingon the battery's
chargelevel.
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01Eng WH18DSDL US.p65 16 10/2/12, 2:38 PM