To provide an easily-manufacturable lock screw that allows firmer screw-engagement between a male screw and a female screw by mechanical screw-engagement even under every condition and effectively exerts a stable and strong screw lock function even at a screw-engagement part with a small screw part.

The lock screw has the following configuration. A thread ridge 5 is provided at an equal interval by forming the ridge of a male screw 1, whose frank angle θ1on the pressure side is formed smaller than a frank angle θ2on the play side, into a non-circular shape. Each inclined protrusion 7 is formed between the inclined face 6 of the frank angle θ1on the pressure side and the root diameter d1of the male screw 1. The looseness preventing screw is configured such that, when the male screw 1 is screwed into a female screw 2, the thread ridge 5 of the male screw 1 is made to bite into the root diameter D1of the female screw 2 while using the inclined protrusion 7 as a fulcrum.

COPYRIGHT: (C)2010,JPO&INPIT