Tightening Torque Inspection Prior To Operation; Tightening Torque Variation - Hitachi WH 10DL Technical Data And Service Manualice Manual

2. Tightening torque inspection prior to operation

The output torque of the Model WH 10DL exceeds the appropriate tightening torque of bolts and screws as
described in "(3) Tightening torque characteristics" on page 8. Accordingly, if the tightening time is
prolonged, the output torque exceeds the appropriated tightening torque and the screws or the bolts may
be damaged or 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 customers 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.

3. Tightening torque variation

The tightening torque of the cordless impact driver or wrench may vary according to 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 on page 7 are useful as a handy reference, and may be utilized as tentative standards.
(1) Voltage of battery
The tightening torque is affected by the voltage output of the battery. The 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
customers are fully aware of and understand this characteristic.
Precautions for use of the lithium-ion battery
The Type BCL 1015 lithium-ion battery is equipped with a protection 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 6 V or lower). This is because the protection
function is activated and 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 temperature under the influence of
grease and different torque coefficients (dependent on manufacturing and finishing processes, and
specified by bolt manufacturers).
(3) Different bolt diameter
Difference in bolt diameter may cause variation of the required levels of tightening torque. Generally,
high tightening torque is required for large bolts.
(4) Different material to be tightened
When a bolt is tightened into a soft material such as aluminum, plastic, wood, etc., the tightening torque
is considerably low in comparison with the tightening torque required for tightening a bolt into a hard
material such as steel.
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