and the impact wrench. These tools operate on
compressed air at a pressure of 90 (+10) psi. The air
supply hose must be a minimum 5/16 inch inside
diameter and should not be more than 15 feet long.
Observe all standard precautions for the use of air-
The torque that the tool will apply to a
fastener at a given torsion bar setting is
dependent to some extent on the bolt
diameter and length, the type of nut,
and the compression characteristics of
the metal in the joint. The shutoff
torque of the tool must be checked and
the torsion bar adjusted as required
when there is any change in any of
these conditions, even though the
required torque remains the same.
8-3. Torque Wrench Selection. The appropriate
torque wrench can be selected for a specific job, based
on the type desired, the range of the tool, and the
appropriate torque units.
a. Types. In aircraft maintenance applications, the
rigid frame with the indicating dial and the audible
indicating torque wrenches are used in preference to the
flexible beam-type wrench. The audible-indicating
torque wrench is preferred since it can be used in places
of limited accessibility where it would be difficult to read
a dial or scale while performing the tightening operation.
For the combinations of features available in torque
wrenches, see figures 8-5 through 8-14.
b. Range. When selecting a torque for a particular
considered. When practical, the required torque value
should be between the 30- and 80-percent points of the
torque wrench range. The accuracy of most torque
Figure 8-6. Type I, Class 1, Style B Torque Wrench - Deflecting Beam with Indicator Plate
(Direct Reading with Feel Impulse and Audible Signal)
Figure 8-5. Type I, Class 1, Style A Torque Wrench - Deflecting Beam with Indicator Plate (Direct Reading)