Prevailing Torque Fasteners
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.
Scheme 1
| 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
| Application | Specification | |
|---|---|---|
| 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 |
Metric Prevailing Torque Fastener Minimum Torque Development
| Application | Specification | |
|---|---|---|
| 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 |
English Prevailing Torque Fastener Minimum Torque Development