Screw e.g. star head screw, manufacturing method, involves emerging recesses in central hole and periphery of driving head, where relative dimensions of hole and recesses permit centering and rotational engagement of cruciform tool

摘要

The method involves machining or drilling a conical and one-eyed central hole (6) on an upper plate part of a driving head (2) of a screw (1). Four quadrangular section recesses are formed radially and perpendicularly with respect to each other by milling or machining on the upper plate part of the head from center of the plate. The recesses are emerged in the central hole and periphery of the head, where relative dimensions of the central hole and the recesses permit centering and rotational engagement of a standard cruciform tool. An independent claim is also included for a screw comprising a shank with three zones.