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8-2. Tightening Torque Inspection prior to Operation
As described and shown in Para. 7-2-3, the output tightening torque of which the Model WH 14DM is 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 wrenches/drivers.) Particularly when tightening M6 (1/4")
or smaller screws, tightening time must be kept extremely short: 0.5 seconds or less. The customer should be
advised to carry out several bolt tightening operations and adjust the tightening time as necessary by measuring
the tightening torque with an appropriate torque wrench before commencing continuous operation.
8-3. Tightening Torque Variation
The tightening torque of the cordless impact wrench/driver 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. 7-2-2 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
battery is fully discharged. As this phenomenon is an inherent drawback in any cordless impact driver,
salespersons are requested to ensure that the customer is fully aware of and understands this characteristic.
(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 (dependent on manufacturing and finishing processes, and 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.
(4) Different materials being tightened
When a bolt is tightened into a soft material such as aluminum, plastic, wood, etc., the tightening torque is
considerably less than when the bolt is tightened into a hard material such as steel.
(5) Different tightening conditions
The tightening torque may vary in accordance with bolt torque coefficient (dependent on manufacturing
process, and specified by bolt manufactures), bolt grade and bolt length, even though the dimensions of the
bolts are the same. Tightening torque may also vary depending on the surface finishing state of tightening
materials (steel, aluminum, etc.), and materials to be tightened. In addition, if there is seal packing, clearance,
etc., between tightening materials, the tightening torque is decreased.
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