Apparatus and method for forging a bicycle crank

摘要

An elongated rod is heated and then inserted into a series of axially spaced die sets each consisting of a pair of mating gripping dies defining a plurality of axially spaced cavities. The rod is gripped by the die sets at axially spaced intervals, and the die sets are then forced axially together by actuation of a press to expand portions of the rod into the cavities and thereby form a plurality of axially spaced enlarged bosses on the rod. The rod is bent to form a set of crank arms integrally connected by an axle portion which has two of the axially spaced bosses. Cylindrical surfaces are forged on the two bosses, and one of the bosses is forged into an outwardly projecting sprocket retaining stud.