Self tapping threaded fastener for securing softer material onto hard base has radial flanges behind the cutting tip and with spiral clearing teeth and groove s for the swarf

摘要

A self tapping screw for fitting softer materials onto a hard base, e.g. for fitting wooden panels onto a metal frame, has a cutting head (6) with radial flanges (7) which widen the drilled hole through the softer material and which are abraded by the harder material. The invention describes spiral teeth (5) and grooves (6) behind the cutting head to clear the swarf to the spiral shaft (1) of the fastener and to prevent build up of swarf. The fastener is driven by a conventional driver engaging the slotted outer head (2, 3).