4-72.STANDARDS.
4-73 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 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 4-16.)
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 + T
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.
C =
1 x 30
1+.25
or C =
30
1.25
= 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 4-16. Torque Wrench Formula
Added: 5/1/80
1F5
* CHEROKEE ARROW III SERVICE MANUAL
STRUCTURES
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