Abstract: A flat disc 1 having a central aperture is deformed on its periphery by spin-forming the metal of the disc so that the metal projects from each side of the plane of the disc and thereby forms a cylindrical rim 6 which is parallel to the axis of the disc. One or a plurality of series of V-grooves 8 are then formed on the outer surface of the rim. The metal is spin-formed in such manner as to cause it to be laterally extruded thereby forming a rim which has a definite thickness independent of the thickness of the initial disc constituting the web of the pulley.