TM 1-4220-250-12&P
APPENDIX F
TORQUE LIMITS
F.1 SCOPE. This appendix lists the standard torque values applied to self-locking nuts (Table F-1) and to tube coupling
nuts (Table F-2) used in the maintenance of the SRU-37/P.
F.2 SELF-LOCKING NUTS . The breakaway torque values listed in Table F-1 provide a means for determining the
reusability of self-locking nuts. Breakaway torque values shall be determined as follows:
a. Install self-locking nut on screw or bolt with a minimum of two screw threads providing through nut. Face of nut
shall not be in contact with any mating surface.
b. Using a torque wrench fitted with an appropriate size socket, slowly remove nut and note torque value at which
nut begins to turn. This is the breakaway torque. Self-locking nuts that do not meet the minimum breakaway
torque value shall be replaced.
Table F-1. Self-Locking Nut Breakaway Torque Values.
Min. Breakaway Torque
Min. Breakaway Torque
Thread Size
(Inch Pounds)
Thread Size
(Inch Pounds)
10-32
2.0
5/8-18
32.0
1/4-28
3.5
3/4-16
50.0
5/16-24
6.5
7/8-14
70.0
3/8-24
9.5
1-12
90.0
7/16-20
14.0
1-1/8-12
117.0
1/2-20
18.0
1-1/8-12
143.0
9/16-18
24.0
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F.3 TUBE COUPLING NUTS . The torque values listed in Table F-2 are for steel tubing with steel coupling nuts.
Specific torque values, applicable to SRU-37/P maintenance, are stated in the pertinent maintenance tasks described in
Chapter 4 of the this manual.
Table F-2. Tube Coupling Nut Torque Limits.
Torque Requirement
Tube O.D.
Hex Nut
(Inch Pounds)
1/4
9/16
135 - 150
3/8
11/16
270 - 300
1/2
7/8
450 - 500
5/8
1
650 - 700
3/4
1 1/4
900 - 1000
1
1 1/2
1200- 1400
1 1/4
2
1200- 1400
F-1/(F-2 Blank)
