SM0486
which does not operate coaxially with the square drive of the torque handle affects
the predetermined torque value.
i. When you compare the second procedure with the first (without regard to
the type of wrench or manufacturer), there are at least four operation principles
which are common to both of the procedures presented and are common to most of the
torque wrenches which you calibrate. These common principles are as follows:
Torque wrenches have to be unlocked before the desired torque value is set
in on their calibrated scales.
The torque wrench has to be locked after it is set for a specific torque
value.
Always apply torque to a nut or bolt with a smooth, steady motion.
A fast
or jerky motion results in an improperly torqued fastener.
When the torque you apply reaches the predetermined value indicated on the
torque wrench (handle) scale, you feel the handle automatically release or
"break."
j. If you have never calibrated a torque wrench, you need to know the
symptoms of common malfunctions and the corrections necessary for torque wrench
calibrating adjustments. When you want to accurately test the tripping points of
the torque wrench, you need an indicating torque measuring device of the Baldwin 4
type to react against the wrench throughout the range of the wrench.
k. Testing devices are normally of two basic types: a spring-loaded type and
a weight type.
Sometimes it is recommended that you use the dead-weight type
because greater accuracy can thus be obtained.
The technical bulletin for the
wrench being tested provides specific instructions on calibration requirements.
The TB should be checked to see if it contains calibration instructions for the
wrench being calibrated.
l. Irregularity in performance of the wrench is classified as consistently
out of calibration throughout the range (consistent error); inconsistently out of
calibration on either the high or low side of the range (progressively higher or
lower throughout the range); or inconsistently out of calibration varying from one
side of the correct value in certain portions of the range to the opposite side of
the correct value in other portions of the range (variation from one side of the
correct setting in the low range to the opposite side in the high range).
m. Since you are not required to be an expert on torque wrenches, you should
not hesitate to use the applicable TB prepared for the torque wrench you must
calibrate.
In all torque requirements, the desired torque value is predetermined
and may be found in the applicable end item instruction and overhaul manual.
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