Abstract: A drill screw having an integral driving shank, head, and entering end portion. The shank has formed on it thread convolutions of uniform outer and root diameters. The entering end portion has a cylindrical portion coaxial with the shank provided with two flutes inclined with respect to the center axis of the cylindrical portion and disposed on opposite sides of it, and end surfaces of roof-shape. Each of the flutes includes conical flute surfaces. The intersection of each of the conical flute surfaces and each of the end surfaces forms a cutting edge. And each of the conical flute surfaces forms a rake angle with respect to one of the cutting edges, while each of the end surfaces forms a relief angle with respect to one of the cutting edges.In a preferred construction each fluted surface is located outside or beyond a plane containing the center axis of the drill screw, and the fluted surfaces each have a vertex angle of 35.degree. to 54.degree..

Abstract: A self-drilling and self-extruding fastener having a constant cross section stem and a tapering end portion terminating in a sharp point. The stem is provided with a pair of screw threads of like configuration. The tapering portion is provided with a third thread which begins at the pointed forward end in a very steep lead angle which functions as a drilling portion and thereafter the lead angle decreases so that the third thread may function to extrude the metal surrounding a guide opening formed by the drilling portion. Depending upon the screw thread configurations, one or both of the screw threads cooperate with the third thread to further extrude sheetmetal surrounding the guide opening into a cylindrical bore, after which the screw threads self-tap into the wall of the cylindrical bore of the projection and thereby firmly grip the sheetmetal.

Abstract: A self-extruding fastener having a head provided with a cross groove, a stem having two screw threads and a tapering portion terminating at a sharp pointed forward end adapted to form a guide opening in a thin sheet of metal. A third screw thread generates in a position midway between said two screw threads and in a portion where the stem ends and the tapering portion begins, and extends to the pointed forward end, while the two screw threads disappear in the tapering portion. Therefore, the self-extruding fastener according to the invention comprises three sections, that is, two screw thread section, three screw thread section and one screw thread section.

Abstract: A drill screw is produced by a pinch pointing die comprising a pair of substantially identical drill point forming portions each of which includes a half conical recess, a half cylindrical recess and a half truncated conical recess. The drill screw thus produced comprises, therefore, substantially identical two half drill point portions each of which includes a half conical portion, a half cylindrical portion and a half truncated conical portion.