UNA MATRIZ PARA USO EN COOPERACION CON UNA MATRIZ COINCI- DENTE, PARA LAMINAR UN FILETEADO DE ROSCA EN UNA PIEZA ELE- MENTAL DE PARTIDA DE SECCION TRANSVERSAL CIRCULAR.

摘要

A method of making a thread-forming screw of arcuate polygonal cross-section from a blank of circular cross-section comprises rolling the blank between thread-rolling dies having a series of spaced apart grooves that are parallel to the longitudinal axis of the blank. The grooves define obtuse angles large enough to permit the blank to roll into and out of the grooves during the thread-forming. The thread thus formed presents a root cross-section formed by an odd number of intersecting circular arcs and a crest cross-section of a like number of circular arcs and respectively concentric with the root cross-section arcs. The arcs at the crest are joined by smaller thread-swaging arcs or lobes that are of a radius substantially equal to depth of the thread.