PIPER COMANCHE SERVICE MANUAL
II - HANDLING AND SERVICING 04/01/09
1B18
2-7. 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.
CA
UTION: DO NOT OVERTORQUE FITTINGS.
NO
TE
: When flared fittings are being installed, ascertain that the male threads are properly lubricated.
Torque fittings in accordance with Table II-II.
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 2-8a.)
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 = A x T
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 = I x 30 or C = 30 = 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 2-8a. Torque Wrench Formula
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