Method of and apparatus for forming a disc-shaped blank

A apparatus 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 said plate material with a roll die to thicken said outer peripheral portion and is shaped into a cross-sectional configuration corresponding to that which is generally a horizontally elongated and vertically shortened letter "U", characterized in that said apparatus comprises:

• a pair of sandwiching members for sandwiching and securing between them, said disc-shaped thin plate material except for said outer peripheral portion including a swaging portion projecting from said sandwiching members;
• swaging means for swaging exclusively said swaging portion so that an outermost end thereof may be shaped into a configuration which in cross-section is generally triangular having an outwardly tapered side surface and a rounded top and thus may also be thick-walled while a root portion of said plate material that is sandwiched between said sandwiching members remains in a thin thickness original of said plate material;
• bending means for bending said outer peripheral portion including said swaged portion at a site adjacent to said root portion thereof from one side surface of said plate material towards a direction of the other side surface thereof and forming a bent portion into an L-shaped configuration in cross section so that said bent portion may lie within a predetermined width;
• and
• forging means for forging said bent portion in a closed state to assume a configuration which is rectangular in cross section so that an inner surface and outer surface thereof may each have predetermined dimensions.