THREAD ROLLING DIES FOR FORMING SELF TAPPING SCREWS AND THE LIKE

摘要

THREAD ROLLING DIES FOR FORMING SELF TAPPING SCREWS AND THE LIKE A method and apparatus for forming self tapping threaded fasteners having a cylindrical gripping portion and a tapered end portion with swaging lobes thereon is disclosed. The apparatus includes a pair of flat dies having a flat G-surface formed with thread rolling grooves therein to form the gripping cylindrical portion of the fastener. A rise angle surface having thread forming grooves therein with lobe forming recesses adjacent to the finished end operate to form the tapered point with lobes thereon. The G-surface is wider at the forward end of the die and progressively narrows until a dwell or finished portion is reached adjacent to the finish end of the die. Consequently, the threads along the tapered portion of the blank are not as fully formed as the threads along the cylindrical portion when the blank reaches the finishing end and excess material is available to fill the recesses and produce the lobes.