A locknut is a special type of nut that resists loosening from vibrations and torque. One of the most common styles is a prevailing torque locknut. This kind of locknut has a prevailing torque feature which deforms elastically, preventing it from freely spinning like a standard nut.
The two most common and reliable forms of prevailing torque locknuts are the flexloc style and the polymer insert lock nut. A flexloc nut is all-metal in composition with a segmented collar that creates six “locking fingers,” that act as a spring. Polymer insert lock nuts are often referred to as nylon insert locknuts, although various high performance polymers can be used for the screw threads to “bite into.” Both flexlock and polymer insert locknuts are available in both hexagonal and 12 point configurations.
Lock Nut Sizes
• #00 - 10"
• M1.2 - M250
|Lock Nut Specifications |
• ASME B18.16.3M
• DIN 980
• DIN 6923
• DIN 985
• DIN 986
• ISO 7042
• ISO 19513
• ISO 4161
• ISO 10511
• ISO 7040
|Mil Spec Lock Nuts |
NASM 25027, MIL-DTL-25027 and MIL-N-25027
MIL-N-25027 is superseded by MIL-DTL-25027; MIL-DTL-25027 is superseded by NASM 25027.
Mil spec NASM25027 covers the requirements for steel, corrosion resistant steel (CRES), aluminum alloy, copper alloy and nickel-copper alloy (Monel 400) self-locking nuts.
• 250˚F nuts
• 450˚F nuts
• 800˚F nuts
|All Metal Flexloc Lock Nut ||Polymer/Nylon Insert Lock Nut |
- Can be used at high temperatures
- Distributes load evenly due to the fact that it is manufactured as one solid piece.
- Is THE most reliable all-metal self-locking nut.
- As it is all metal, it is best for high temperature or corrosive applications
- One of the only all-metal lock nuts that is certified to 15 cycles of prevailing torque – which is military standard.
- Overall the most reliable locknut, with the only limitation of application temperature
- Best for low temp applications, typically less than 350°F
- Various polymers inserts available (Nylon, Vespel, PVDF, etc.) for higher temp. or corrosive applications.
- Excellent reusability – can reliably be re-used 15 times
- Eliminates galling and cold-welding common with exotic alloys
Additional Lock Nut Styles
Other all metal lock nuts available include the stover and elliptical styles. Though these styles are often a cheaper initial cost, they are less reliable than the flexloc style. As these styles delivering less prevailing torque cycles and often result in more failures, the flexloc style is a better investment for both reliability and cost savings.
Lock Nut Availability