Torque Wrenches; Torque Wrench Formula - Piper Navajo Chieftain PA-31-350 Service Manual

A933
NAVAJO CHIEFTAIN SERVICE MANUAL
2-9. 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 2-3.)
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 xT
A+B
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.
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.
A
Figure 2-3. Torque Wrench Formula
Reissued: 9/23/80 lB9
HANDLING AND SERVICING