Prevailing Torque Fasteners

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Prevailing torque fasteners create a thread interface between the fastener and the fastener counterpart in order to prevent the fastener from loosening.

All Metal Prevailing Torque Fasteners

These fasteners accomplish the thread interface by a designed distortion or deformation in the fastener.

Nylon Interface Prevailing Torque Fasteners

These fasteners accomplish the thread interface by the presence of a nylon material on the fastener threads.

Adhesive Coated Fasteners

These fasteners accomplish the thread interface by the presence of a thread-locking compound on the fastener threads. Refer to the appropriate repair procedure in order to determine if the fastener may be reused and the applicable thread-locking compound to apply to the fastener.

Fig 1: Identifying Adhesive Coated Fasteners

Courtesy of GENERAL MOTORS COMPANY

Callout	Component Name
1	Prevailing Torque Nut, Center Lock Type
2	Prevailing Torque Nut, Top Lock Type
3	Prevailing Torque Nut, Nylon Patch Type
4	Prevailing Torque Nut, Nylon Washer Insert Type
5	Prevailing Torque Nut, Nylon Insert Type
6	Prevailing Torque Bolt, Dry Adhesive Coating Type
7	Prevailing Torque Bolt, Thread Profile Deformed Type
8	Prevailing Torque Bolt, Nylon Strip Type
9	Prevailing Torque Bolt, Out-of-Round Thread Area Type

A prevailing torque fastener may be reused ONLY if:

The fastener and the fastener counterpart are clean and not damaged
There is no rust on the fastener
The fastener develops the specified minimum torque against its counterpart prior to the fastener seating

Metric Prevailing Torque Fastener Minimum Torque Development

Application	Specification
Application	Metric	English
All Metal Prevailing Torque Fasteners
6 mm	0.4 N.m	4 lb in
8 mm	0.8 N.m	7 lb in
10 mm	1.4 N.m	12 lb in
12 mm	2.1 N.m	19 lb in
14 mm	3 N.m	27 lb in
16 mm	4.2 N.m	37 lb in
20 mm	7 N.m	62 lb in
24 mm	10.5 N.m	93 lb in
Nylon Interface Prevailing Torque Fasteners
6 mm	0.3 N.m	3 lb in
8 mm	0.6 N.m	5 lb in
10 mm	1.1 N.m	10 lb in
12 mm	1.5 N.m	13 lb in
14 mm	2.3 N.m	20 lb in
16 mm	3.4 N.m	30 lb in
20 mm	5.5 N.m	49 lb in
24 mm	8.5 N.m	75 lb in

English Prevailing Torque Fastener Minimum Torque Development

Application	Specification
Application	Metric	English
All Metal Prevailing Torque Fasteners
1/4 in	0.5 N.m	4.5 lb in
5/16 in	0.8 N.m	7.5 lb in
3/8 in	1.3 N.m	11.5 lb in
7/16 in	1.8 N.m	16 lb in
1/2 in	2.3 N.m	20 lb in
9/16 in	3.2 N.m	28 lb in
5/8 in	4 N.m	36 lb in
3/4 in	7 N.m	54 lb in
Nylon Interface Prevailing Torque Fasteners
1/4 in	0.3 N.m	3 lb in
5/16 in	0.6 N.m	5 lb in
3/8 in	1 N.m	9 lb in
7/16 in	1.3 N.m	12 lb in
1/2 in	1.8 N.m	16 lb in
9/16 in	2.5 N.m	22 lb in
5/8 in	3.4 N.m	30 lb in
3/4 in	5 N.m	45 lb in