TWIN-LOCK locking washers: ensures against loosening of transverse-loaded, movable- or vibrating bolt connections, applicable with hexagon head bolts, hexagon nuts, etc. The twin lock system consist of two identical washers which have external protruding ribs on one side, and inclined facets on the other
The inclined angle of the facets is larger than the pitch angle of the thread of the bolt or nut. The twin lock washers are assembled in pairs, with the inclined facets facing each other, During tightening the protruding ribs of one washer are pressed into the contact surface of the nut or bolt, and the protruding ribs of the other washer are pressed into the work-piece. Simultaneously slot the inclined facets perfectly into each other, Should a bolt or nut loosen, then the twin lock washer will turn with it, causing the two washers to press against each other. The inclined facets rotate the washer (also the bolt/nut) higher than the thread permits, resulting in a self locking action,
Loosening of a nut or bolt, due to vibration etc. will result in a strengthened locking action. To ensure a good surface contact of the protruding ribs, 20% more torque than normal is required. By dis-assembly is a normal torque sufficient to loosen the connection, while the remaining tension is increased by only 10%.