DIN 25201 Wedge Lock Washers

DIN 25201 Wedge Lock Washers are mechanical locking elements used to prevent bolted joints from loosening under vibration, transverse movement, and other dynamic loading. Unlike conventional split spring washers, the locking action comes from a pair of washers with wedge-shaped cam surfaces on one side and radial serrations on the opposite side. The two washers are normally supplied as a bonded pair and installed together.

The wedge-locking principle is based on relative movement between the two washers. When a bolt or nut attempts to rotate loose, the cam surfaces force the washer pair to expand axially while the outer serrations grip the mating surfaces. This converts the loosening movement into additional clamping resistance rather than relying primarily on friction. The arrangement makes DIN 25201 washers particularly relevant to joints exposed to vibration, oscillation, or changing transverse loads.

Common market terms include wedge lock washer, wedge locking washer, wedge washer, and twin washer. DIN 25201 does not have an ISO equivalent listed in standard references, so the DIN designation remains important when specifying the product. Variants are available with different contact diameters, including narrow and wide forms, allowing the washer pair to be matched to the available seating area and joint geometry.

Typical applications include mechanical equipment, vehicle manufacturing, agricultural machinery, mining equipment, conveying systems, power and pneumatic tools, and other bolted assemblies subject to dynamic loads. Selection should consider bolt size, available seating surface, mating-surface hardness, joint geometry, and the required washer material and finish.