Internal/External Tooth Lock Washer

A tooth lock washer is a thin washer with teeth on the inner or outer edge. The teeth bite into the mating surfaces to resist loosening from vibration.

An internal or external tooth lock washer grips a joint and resists loosening under vibration. It usually sits under a nut or a bolt head, with the teeth facing the mating surface. It is often matched with a bolt or screw of the same thread.

This kind of washer is often made in spring steel or stainless steel. The material choice affects corrosion resistance and how well the teeth grip.

This is a general guide to checking this kind of part. It says nothing about any supplier's parts.

Ask for a certificate of conformance if you need proof of material or dimensions. On receipt, check tooth form, hardness and that the washer sits flat.