Fastening arrangement employing thread-forming screw

摘要

A fastening arrangement comprising a thread-forming lobular screw (20) and a member (40) defining a non-tapped pilot hole (50) therein. The screw has a shaft (22) and a head (24) joined to a proximal end of the shaft, the shaft defining a plurality N of lobes (28) circumferentially spaced about a central longitudinal axis of the shaft, a thread (26) being formed on an outer surface of the shaft. The pilot hole comprises a central portion (52) of a diameter intermediate the minor (d) and major (D) diameters of the screw thread, and a plurality N of circumferentially spaced cutouts (54) extending radially out from the central portion. A plurality of longitudinally extending edges (50) parallel to the axis of the screw are defined at junctures between the cutouts and central portion of the pilot hole. The screw thread forms a thread in the member beginning at the longitudinal edges of the pilot hole.