STANDARD PRACTICES - AIRFRAME.
TORQUE WRENCHES.
Torque wrenches should be checked daily and calibrated by means of weights and a measured lever arm to
make sure that inaccuracies are not present. Checking one torque wrench against another is not sufficient and
is not recommended. Some wrenches are quite sensitive as to the way they are supported during a tightening
operation. Any instructions furnished by the manufacturer must be followed explicitly.
When it is necessary to use a special extension or adapter wrench together with a torque wrench, a simple
mathematical equation must be worked out to arrive at the correct torque reading. Following is the formula to
be used: (Refer to Figure 20-1.)
T = Torque desired at the part.
A =Basic lever length from center of wrench shank to center of handle or stamped on wrench or listed
for that model wrench.
B =Length of adapter extension, center of bolt to center of shank.
C =Scale reading needed to obtain desired torque (T).
The formula: C =
EXAMPLE
A bolt requires 30 foot-pounds and a 3-inch adapter (one-quarter of
a foot or .25’) is needed to get at it. You want to know what scale
reading it will take on a one-foot lever arm wrench to obtain the 30
foot pounds at the bolt.
C= or C = = 24 ft.-lbs.
Remember, the 3-inch adapter must be projecting 3 inches straight
along the wrench axis. In general, avoid all complex assemblages
or adapters and extensions of flex joints.
Figure 20-1. Torque Wrench Extension
30
1.25
1 x 30
1 + .25
A x T
A + B
20-00-01
Page 20-01
December 1, 1978
1E16
PIPER AIRCRAFT
PA-28RT-201 / 201T
*MAINTENANCE MANUAL
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