Locking washers

A washer having a screw-thread formed in a central bore thereof to enable the washer to be screwed onto a screw-threaded bolt member the washer being adapted for tensioning itself against a surface when screwed up against the surface for increasing friction between the washer and the screw-threaded member;

• wherein the washer is resilient and substantially dish-shaped for tensioning itself against said surface, and is formed with at least one peripheral recess therein defined by two edges one of which passes substantially radially inwardly from the periphery of the washer and the other of which passes along a line such that said one edge is not faced by said other edge of the recess, such that when said washer is screwed up and tensioned against said surface and in flattened condition, there is exerted a constant locking force by said washer regardless of the position to which the bolt member is thereafter screwed.