Tightening Torque Inspection Prior To Operation; Tightening Torque Variation - Hitachi WH 14DSL Technical Data And Service Manual

8-2. Tightening Torque Inspection Prior to Operation

As described and shown in Para.7-3-3, the output tightening torque of which the Models
WH 14DSL and WR 14DSL are capable in excess of the rated tightening torque of certain bolts
and screws. Accordingly, if the tightening time is prolonged for such bolts and screws, it could
cause damage to their threads or, in the worst case, cause them to be sheared off. (This
phenomenon is common to all existing impact drivers.) Particularly when tightening M6 (1/4") or
smaller screws, tightening time must be kept extremely short: 0.5 second or less. The customer
should be advised to carry out several screw tightening operations and adjust the tightening time
as necessary by measuring the tightening torque with an appropriate torque wrench or driver
before commencing continuous operation.

8-3. Tightening Torque Variation

The tightening torque of the cordless impact driver or wrench may vary slightly in accordance with
the factors described below. Salespersons are requested to advise the customer to confirm that
appropriate tightening torque is obtained by measuring the torque with an appropriate torque
wrench or torque driver at the beginning of the tightening operations, and as necessary during the
tightening operations. In addition, the torque values shown in Para. 7-3-2 above are useful as a
handy reference, and may be utilized as tentative standards.
(1) Voltage of battery
Tightening torque is affected by the voltage output of the battery. Tightening torque decreases
as the number of bolts tightened increases. This phenomenon is caused by the decline in
voltage output of the battery due to the increasing number of bolts tightened. In particular, the
tightening torque decreases rapidly just before the overdischarge protection circuit is activated.
As this phenomenon is an inherent drawback in any cordless impact driver/wrench,
salespersons are requested to ensure that the customer is fully aware of and understands this
characteristic.
Precautions for use of the lithium-ion battery
The lithium-ion battery is equipped with a protective function that automatically stops output to
extend the battery life. The motor may stop automatically even though the switch is depressed
continuously when the remaining battery level is low (about 8 V or lower). This is because the
protective function is activated. The battery is not faulty. Charge the battery immediately in
such case.
(2) Effects of low ambient temperatures
The tightening torque required may be reduced at low ambient temperatures or under the
influence of grease and different torque coefficients (depending on manufacturing and
finishing processes specified by bolt manufacturers).
(3) Different bolt diameter
Differences in bolt diameter will cause variation of the required levels of tightening torque.
Generally speaking, tightening torque is higher for large bolts.
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