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Lock Washers Basics

Lock washers are used under bolt heads or nuts to increase the hold of the fastener and prevent loosening.

Split Lock Washers

Split lock washers are helical-shaped split rings. When fastened, the two ends exert a spring force on the fastener to create increased friction and resistance to motion.

Tooth Lock Washers

Internal tooth lock washers and external tooth lock washers have teeth on the inner or outer (respectively) perimeter of the washer creating a ratchet action by biting into the nut or screw head and the surface it contacts, thereby preventing unwanted rotation.

Nord-Lock Washers

Nord-Lock wedge-locking washers utilize tension as a means of exponentially increasing friction in order to secure bolted joints exposed to severe vibration and dynamic loads. Nord-Lock washers are used in paired sets. The system comprises of a pair of wedge-lock washers with cams on one side and radial teeth on the opposite side. As the fastener attemptsĀ to loosen, the unique design of the Nord-Lock's interior wedge design causes increased tension on the fastener, stopping the unwanted rotation.

Common Finishes of Lock Washers

Steel lock washers are available in a variety of finishes and coatings, which play a role in the suitability of the fasteners in different applications, such as enhancing resistance to corrosion from environmental elements or chemicals. Coatings also greatly effect consistency of torque values for installation, and ease of disassembly at the end of service.

Black or Plain Finish Lock Washers

Lock washers are unfinished or will have a minimally protective finish. Black lock washers offer near zero corrosion resistance, though black oxide coatings or oiled coatings do offer increased corrosion resistance over unfinished lock washers.

  • Black lock washers are commonly referred to as plain finish, black, black oxide, black phosphate, bare or light oil coated.

Galvanized Lock Washers

Lock washers are coated with a sacrificial zinc coating that acts as an anode to prevent the fastener underneath from corroding.

  • Hot Dipped Galvanized: Fasteners are dipped in a bath of molten zinc.

Plated Lock Washers

Lock washers are coated with a thin layer of zinc, typically via electroplating.

  • Plated lock washers will not corrode as quickly when covered with this protective coating, even when a scratch or cut exposes the steel to air or moisture. The zinc or cadmium plating will always tarnish and corrode first.