Abstract: An appratus and method for manufacturing a pulley having a generally V-shaped groove therein is provided. The apparatus includes a press section and a molding section. The starting material for forming the pulley is a ring-shaped workpiece which is preferably composed of a bendable metal. The apparatus clamps the workpiece about a central annular portion thereof. Other parts of the apparatus bend upper and lower annular portions of the workpiece radially outwardly, thereby forming a V-shaped groove. The pulley is formed by a single thrusting motion of the press section. The bottom portion of the V-shaped groove has a uniform thickness which is not thinned by the action of the press.

Abstract: A method for manufacturing a rotor frame of an electromagnetic clutch is disclosed. A rotor frame is manufactured using press machines in a sequential process of: (1) forming a blank which has the shape of a regular polygon; (2) forming a bulge in one side of the blank; (3) making a hole in the center of the bulge; and (4) bending the walls of the bulge and the blank edges into projections that can be machined to provide appropriately shaped end surfaces for use as a rotor frame.