Nylon Insert Lock Nuts

Nylon insert lock nuts — widely called Nylock nuts — have a nylon collar at the top that the bolt threads cut into, creating friction that resists loosening from vibration. They are one of the most reliable and reusable prevailing-torque locking nuts, used throughout automotive, machinery, and equipment assembly. We stock nylon insert lock nuts across every common material and size.

How They Work

The unthreaded nylon insert is slightly smaller than the bolt's major diameter. As the bolt advances, it taps threads into the nylon, and the collar grips the threads to prevent back-off under vibration. Because the locking action is mechanical friction rather than thread deformation, the nut can be removed and reused several times before the nylon wears.

Temperature Limit

The nylon insert limits service temperature to roughly 250°F (120°C). Above that, the nylon softens and loses its locking grip. For high-temperature applications, use an all-metal prevailing-torque lock nut instead.

Materials and Finishes

Steel with zinc plating: the economical standard. 18-8 stainless: general corrosion resistance. 316 stainless: marine and chemical environments. The nylon insert is the same across materials; only the nut body changes.

Dimensional Standards

Inch nylon insert lock nuts follow standard hex nut dimensions; metric versions follow DIN 985 (thin) and DIN 982 (thick/high). Both use the nylon insert per the locking specification.

Selecting the Right Nylon Insert Lock Nut

Match thread size and pitch to the bolt, and material to the fastener and environment. Keep service temperature below 250°F. For best locking, use with a bolt that projects fully through the nylon. Where reuse or temperature exceeds nylon's limits, choose an all-metal lock nut instead.

Use the filters to narrow by size, material, and finish.