1. A threaded self-tapping bushing adapted to be secured to a workpiece and comprising, an elongate member having helical male threads extending over at least a portion of its axial length said threads having crests, roots between said crEsts, and flanks extending from said crests to said roots on either side of said crests; said member having at least one axially extending bevel intersecting a plurality of successive threads, the crests and flanks of each said male thread at their intersection with said bevel defining frontal areas on either side of said bevel which are concave both along the circumferential direction of each said male thread and transversely thereto along the axial direction of the bushing, each said bevel being approximately as deep as the roots between the crests to ensure that the roots between successive crests are essentially discontinuous at each bevelled portion, each said frontal area providing cutting edges along at least a part of its periphery as defined by said crest, flanks, and bevel, one of the two said frontal areas formed at the junction of each said male thread with said bevel having a greater curvature than the other.