Table 16-4.--Approximate Torque Required to Obtain
Bolt-Stud Stress of 25,000 psi and 30,000 psi in Various
Sizes of Alloy Steel Bolts and Studs (UNC)
Approximate
Nominal Size
Approximate
Torque
Torque
(inches) of
(foot-pounds)
(foot-pounds)
Alloy Steel Bolt
Required to Obtain Required to Obtain
or Stud
30,000 psi Stress
25,000 psi Stress
Figure 16-22.--Bolt-stud measurements.
30
1/2
25
5/8
50
60
314
83
100
has been compressed enough, and it prevents excessive
160
718
133
245
1
205
compression of the gasket and overstressing of the
355
1-M
295
bolt-stud.
500
416
1-1/4
Bolt-stud stress is checked by measuring the overall
645
1-3/8
567
length of the bolt-stud before and after installation to
800
1-1/2
667
determine the total amount of stretch (elongation). The
total amount of stretch is then divided by the effective
length of the bolt-stud to determine the stretch per inch
The approximate torque required for bolt-stud
of effective length.
stresses of 25,000 psi and 30,000 psi is shown in table
The effective length of a bolt-stud is generally
16-4.
considered to be the distance from the center of one nut
These figures assume that the threads (UNC) are
to the center of the other nut (fig. 16-22).
well lubricated. Torque wrenches should be used to
Naval shipyards and repair ships are equipped with
apply the initial bolt-stud stress. The dial of the torque
strain gauges for measuring bolt-stud elongation. When
wrench indicates the torque (in foot-pounds) applied.
strain gauges are not available, use the best micrometer
The torque values given in table 16-4 should be applied
to obtain the required stress.
calipers, use a C-frame, such as the one shown in figure
Bolt-stud stress must be checked by measuring the
bolt-stud elongation. This check ensures that the gasket
16-23.
Figure 16-23.--C-frame gauge for measuring bolt-stud elongation.
16-21