An extruding and thread forming screw
An extruding and thread forming screw fastener including a cylindrical shank, a head at one extremity of said shank, and a cylindrical pilot section of smaller diameter than said shank at the opposite entering extremity of said shank in coaxial alignment with the shank section and a work swaging portion interposed between said pilot section and said shank section, the lowermost extremity of the work swaging portion in the vicinity of its juncture with said pilot portion defining a plane at an acute angle to a plane perpendicular to the axis of the shank and pilot of said screw, the work swaging surface diverging upwardly and outwardly in substantially a conical configuration and defining at the juncture with said shank a plane substantially angularly disposed to the axis of said shank in the same direction as the plane at the juncture of the pilot portion and the work swaging surface, said shank provided with threads a portion of which threads extends downwardly toward the entering end into a circumferential segment of said work swaging portion in the vicinity of the portion of said plane nearest the entering end of the screw, a portion of the surface of said work swaging portion opposite said threaded segment being unthreaded and providing a swaging surface to extrude marginal portions of an aperture in a complementary workpiece into which said screw fastener is adapted to be rotated.
The present invention relates generally to threaded fasteners and more particularly twin screw extruder to extruding and/or thread-forming screw fasteners for application to sheet metal. An embodiment of the invention disclosed herein includes a shank having a threaded section, a head at one extremity, a pilot section at the opposite extremity in coaxial alignment with the threaded section and a work swaging substantially conical section interposed between the pilot and threaded shank sections. The conical section is positioned out of axial alignment with the threaded and pilot sections.
More specifically, the present invention envisions a unique and improved extruding and/or thread-forming fastener equipped with an entering end of novel construction which serves to greatly reduce the rotative force required to apply the fastener to an apertured workpiece. Still more specifically, the present invention contemplates the provision of a novel and practical extruding and/or thread-forming screw fastener which will enhance the ease with which the sheet material in the vicinity of the screw accommodating aperture may be swaged to provide an axial extrusion in which thread convolutions subsequently may be formed.