METHOD OF MANUFACTURING HOLLOW PISTON FOR DISC BRAKE, AND HOLLOW PISTON MOLDED BY THE SAME MANUFACTURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a piston at low cost by manufacturing a hollow piston with a groove molded to support an externally fitted dustproof boot, via spinning work wherein a circular steel plate is machined in a rotatively supported position, and simplifying the working process. SOLUTION: A method of manufacturing a hollow piston for a disc brake is so designed that a rotary tool 18 comprising a rotational molding die 14 and a pressure die 16 holds a central portion 12A of a circular steel plate 12 in a clamping manner, a spinning roll 10a irons out a peripheral portion 12B of the circular steel plate 12 along the rotational molding die 14 while the rotary tool 18 is rotated to mold a cupped piston 12', and a formed roll 10b presses on the cylindrical periphery of the cupped piston 12' to form a groove for supporting an externally fitted dustproof boot near a piston opening end.