Arrangement for forming metal parts

摘要

In accordance with this invention a part having an internally threaded section is formed by a progressive stamping operation in which there is only opposed rectilinear motion between the punch and die, and no mandrel is used. The part may include a U-shaped receptacle portion and a prong element for being bent over an object that is supported. In producing the part, grooves are formed in the surface of the workpiece, being progressively deepened to the depth of the screw thread and with side wall portions progressively given the inclination of the flanks of the screw threads. The threaded portion then is given a concave shape at either of its two opposite edges and a convex shape in between. The convex shape subsequently is made concave as the threaded section is closed up. In these steps the part is engaged by punch elements in the form of threaded members which have ridges corresponding to the grooves in the workpiece. Finally, the opposite edges of the grooved portions of the workpiece are brought together and this portion of the workpiece is given a cylindrical shape by compressing it in opposed die openings, completing the threaded section.