Method of cold-forming toothed wheels

Abstract

A method of forming a one-piece sheet metal toothed wheel comprising the steps of rotating (1) a rotary holding unit with the preform secured thereto about the preform axis and an inner portion of an outer annular section of the preform within a back-up space provided by the holding unit, and (2) a tooth-forming tool unit about the rotational axis thereof in a predetermined rotational relation wherein the axes are parallel and the rotational speeds are synchronized, and then while the rotary holding unit with the preform secured thereto and the tooth-forming tool unit are in the predetermined rotational relation affecting relative movement between the units and the axes thereof in a direction toward one another to engage the tooth-forming periphery fo the tooth-forming tool unit in cooperation metal-deforming relation with the outer portion of the outer annular section inwardly of the exterior periphery the preform until the sheet metal of the outer portion of the annular section is cold-formed into the series of teeth and displaced from the troughs therebetween so that after the series of teeth are cold-formed the toothed wheel includes a back-up portion having surfaces conforming to the back-up space, the peripheries of the series of teeth being cold-formed by rolling contact with the tooth-forming periphery of the tooth forming tool unit and the sides of the series of teeth including portions disposed outwardly beyond the spaced tooth side defining planes being free-formed without surface, contact by the axially outward movement of the metal defining the outer portion of the outer annular section.