Self-tapping headless lobular insert forming method - forms longitudinally spaced chamfers or bevels on rod by orbital or helicoid movement of latter, using rod side surfaces as guide

摘要

The method involves first forming an elongated rod or bar into a specific desired lobular cross-sectional configuration. A number of longitudinally spaced-apart chamfer or bevel portions are then formed by an orbital or helicoid movement of the rod. This movement employs the side surfaces of the rod as a guide, to provide lobular chamfers which comprise smooth continuations of the external lobular configuration. The bevelled rod is then passed through a two die rolling machine in such a manner that the rod describes a helicoid path as it advances, thus forming a thread on its peripheral portions and on adjacent portions of the bevels.