Method of and apparatus for forming a disc-shaped blank

There is provided a method for forming a disc-shaped blank in which a disc-shaped thin plate material is, at an outer peripheral portion thereof, swaged towards an axial side of the plate material with a roll die to thicken the outer peripheral portion and is shaped into a cross-sectional configuration corresponding to that of a dish, the method comprises the steps of: sandwiching and securing between a pair of sandwiching members the disc-shaped thin plate material except for the outer peripheral portion including a swaging portion; swaging the swaging portion projecting from the sandwiching members so that an outermost end of the swaging portion may be shaped into a cross-sectional configuration corresponding to that of an arrowhead while a root portion of the swaging portion has the same thickness as the original thin thickness of the plate material; thereafter, bending the outer peripheral portion including the thick-walled swaged portion at the root portion thereof from one side surface of the disc-shaped thin plate material towards the other side direction and forming a bent portion into an L-shaped configuration in cross section so that the bent portion may lie within a predetermined width; and thereafter, forging the bent portion in a closed state so that an inner surface and outer surface thereof may each have predetermined dimensions.