STAINLESS STEEL NYLON INSERT NUTS

Nylon Insert Nuts — A nylon insert nut — commonly called a nyloc — is a standard hexagon nut with a hexagonal nylon collar pressed into the top, sized with an internal diameter very slightly smaller than the bolt thread. As the bolt is driven through, it has to deform the nylon rather than just pass through a clean tapped hole, and that deformation grips the thread crests continuously, generating prevailing torque that resists rotation even with no axial clamp load on the joint — a fundamentally different locking mechanism from a plain nut, which depends entirely on friction under tension. That's why nylocs are the default choice wherever vibration, impact, or repeated movement risks backing off a plain nut: automotive assemblies, machinery, transport applications, general engineering, anywhere a split pin or castellated arrangement would be impractical or overkill for the load involved. The trade-off is temperature: standard nylon inserts have a limited service temperature ceiling, and above it the polymer softens and loses its grip, so an all-metal self-locking nut (such as Art.980 or a PAL nut) is the better specification for anything running hot — exhaust brackets, ovens, or industrial plant with elevated ambient temperatures. Nylocs are reusable a limited number of times, but each removal and refitting permanently deforms the nylon a little further, so locking performance degrades with reuse; safety-critical joints should get a fresh nut after disassembly rather than the same one refitted repeatedly. A2 stainless suits the majority of general applications; A4 is worth specifying for marine, washdown, or continuously outdoor assemblies where corrosion resistance matters as much as the mechanical lock. Thread size, pitch, and coarse-versus-fine variant must match the mating bolt exactly, and where extra thread engagement is wanted alongside the nylon lock, the taller DIN 982 high-type nut is worth considering instead of the standard height.

FAQs
How many times can a nyloc nut be safely reused?
There's no hard number — locking performance drops a little with each removal and refitting as the nylon deforms further, so as a rule of thumb a nut that's been removed more than once or twice should be treated with caution, and any safety-critical joint should get a fresh nut.

Should I choose a standard, fine pitch, or high-type nyloc?
Standard coarse pitch suits most general applications; fine pitch (DIN 985) is worth it for vibration-prone or thin-section joints; the high type (DIN 982) is the better choice where the joint needs more metal-to-metal thread engagement for higher load capacity alongside the nylon lock.

Does a nyloc nut need to be fitted a particular way round?
Yes — the nylon collar end must face away from the joint so the bolt passes through the full metal thread first and engages the nylon last; fitting it backwards means the nylon does the initial alignment work and can be damaged before the nut seats.

Is a washer needed under a nyloc nut?
Not for the locking action itself, which comes entirely from the nylon collar, but a washer is still worth using where load spreading over a soft or oversized-hole surface is needed, exactly as with any other nut.