Patent ID: 7360388

Claim:
A method of forming a hollow stepped shaft, comprising: extruding a solid rod blank from opposite axial ends of the blank with a first punch and a second punch while restraining an outer periphery of the blank, so as to form a pair of axial hollows in two axial parts of the blank, respectively, and such that a solid plug portion of the blank remains between the pair of axial hollows; compressively moving one of the first and second punches to shear the solid plug portion out of the blank so as to form a hollow blank having a single continuous axial hollow formed from the pair of axial hollows; and extruding the hollow blank forwards and backwards with a third punch and a fourth punch so as to form a stepped portion that is enlarged in both diameter and thickness in a region of the blank that is one of: (i) intermediate between the opposite ends of the blank and (ii) at one of the ends of the blank, while simultaneously making the blank longer.