Threaded fastener, and method and rolling dies for making it

摘要

A fastener (20) has a substantially parallel portion (12) with a head (13) at one end and a tapered portion (14) leading to a point (15) at the other end, and a helical formation (21) providing an edge (23) along its length and extending outwardly from the body, wherein the helical formation (21) starts substantially at the point (15). The fastener (20) is made by means of a pair of rolling dies, and the helical formation 21a is of different cross-section to that of helical formation 21 b. The fastener may comprise a two start thread.