TM 1-1500-204-23-9
wrenches trends to decrease at the extremes of the
torque range. The best accuracy is obtained between
the 30- and 80-percent points of the range. The
graduation increments on the torque wrench should not
be greater than 10 percent of the torque value being
measured. Refer to table 8-1 for the accuracy limits for
torque tools.
c. Appropriate Units. The torque wrench should be
calibrated in the same torque units (inch- pounds, foot-
pounds, etc.) as are used to specify the torque for the
fastener.
8-4. Determining Correct Torque Value. There is a
correct torque value for tightening every fastener. In
some instances, the torque value will be given in the
maintenance manual with the detailed instructions for
the assembly or the installation of the components. In
most instances, the torque value will be obtained from a
table, similar to table 8-2, in the general instructions
section of the aircraft maintenance manual. Table 8-2 is
a standard table of recommended torque values for
tightening different types of standard nuts. This table, or
its equivalent, should be consulted for the correct torque
value for any fastener that does not have a torque value
specified in the assembly instructions.
8-5. Torque Wrench Operation and Use. To properly
use a torque wrench, the mechanic must pos
Table 8-1. Torque Tool Accuracy Limits
Test instrument
Performance
parameters
specification
Torque Wrenches
Range: 0 to 1000 foot-pounds
Accuracy: (±4 percent) of
reading from 20 percent of full
scale to full scale.1
Torque
Range:
Screwdriver
0 to 100 inch-pounds
Accuracy: ( 3 percent
1No accuracy requirement from 0 to 20 percent of full
scale of wrench.
sess a basic knowledge of essential related details, and
must exercise a reasonable amount of care and skill.
a. Force Application. A smooth, steady force must be
applied to obtain accurate torque values. Rapid or jerky
force can result in considerable error in the torque
applied.
Figure 8-7. Type I, Class 2, Style A Torque Wrenches - Deflecting Beam with Indicating
Dial (Direct Reading)
8-3
