Dies for making thread-forming fasteners

摘要

A self-threading fastener has circumferentially spaced thread-forming lobes on its thread, and with a thread depth at a maximum at the lobes and a minimum circumferentially between the lobes. A lobe in one turn is circumferentially offset from a lobe in an adjacent turn. The fastener is made on roll-threading dies each having grooves sinulsoidally varying in depth from a maximum at one region to a minimum at a second region. The spacing of the regions is equal to a fraction of the thread pitch multiplied by the cosecant of the thread helix angle.