Fastener screw having improved installation and self-locking characteristics

Claim 1

A fastener screw comprising a unitary body having a head portion and an elongated shank coaxial with said head portion, said head portion having a generally planar end surface disposed substantially transverse to the longitudinal axis of said shank and having a drive recess therein, said head portion having an underside defined by a generally concave annular surface interposed between said end surface and said shank, said shank having an external thread thereon terminating in a pointed end to facilitate entry of the screw into a workpiece, said external thread having a generally longitudinal chip relief slot formed therein adjacent said pointed end so as to define a longitudinal cutting edge, and a plurality of outwardly projecting serrations formed about the periphery of said concave surface, each of said serrations extending substantially from said end surface to said shank and being inclined relative to the longitudinal axis of the screw in the direction of the thread lead angle so that said serrations burr into the workpiece and effect a self-locking action therewith as the screw is threaded into the workpiece.