Identify the following types of nuts: Which nut has a built-in locking feature using a nylon insert?

• A. Hex Nut
• B. Nylon Insert Lock Nut
• C. Cap Nut
• D. Wing Nut

Answer: (B)

Nylon insert lock nuts use a built-in locking feature: a nylon insert inside the nut that deforms against the bolt threads as you tighten. The nylon is softer than metal, so when the nut is threaded on, the threads bite into the nylon and cause friction plus a slight spring-like pressure. This locking action makes the nut resistant to loosening under vibration and dynamic loads, so it can stay secured without needing a separate lock washer. They’re commonly called nyloc nuts and are handy when you need reliability in conditions with movement but still want to remove or re-tighten later.

Regular hex nuts don’t have any locking mechanism, cap nuts are just domed cosmetic covers, and wing nuts are designed for hand tightening rather than locking, so they don’t provide the built-in locking action of the nylon insert.