A prevailing-torque nut with a nylon collar crimped into its top, sized slightly smaller than the bolt's major diameter so the bolt thread presses its own path into the plastic and the friction resists backing off. The clipped trade name is used for every brand. Nylon inserts are limited to roughly 120 C (250 F) and lose much of their grip after a few reuses; an insert that spins on by hand is finished.
Toss the old nylocs from the swing arm, they spin right on by hand, and grab new ones from the bin.
The bolt should stand at least two threads proud of the nylon; flush with the insert means the lock is barely working.
Also heard as
- nylock
- nylon lock nut
- nylon insert nut
Related terms
Prevailing-torque nut
A nut built to resist turning on the thread before it seats, using a nylon insert or deliberately distorted threads.
Self-loosening
A tightened nut or bolt turning loose by itself, usually because sideways slip in the joint lets it walk off.
Nut
An internally threaded part that mates with a bolt or stud, graded so the bolt breaks before the nut strips.