SELF COUNTER-SINKING SCREW

摘要

A self-countersinking screw including an inverted-conical head portion formed at a top with a cavity adapted to receive a tip of a screwdriver and having a conical bottom, said conical bottom having a plurality of triangula r recesses each having a lateral side extending inwardly to form a sharp edge and a space for receiving chips, a threaded portion, and a tapered portion havin g a large diameter connected with the head portion and a small diameter connecte d with the threaded portion, whereby the sharp edge will make a countersink on a workpiece when the countersunk head screw is turned therein.