Patent ID: 7047781

Claim:
A method of forming a thickened annular peripheral wall of a sheet metal member, comprising the steps of: holding the sheet metal member and forming from the sheet metal member a base plate, a stepped portion and a flange-shaped portion connected integrally by the stepped portion with an outer periphery of the base plate; inserting the base plate, the stepped portion and at least a part of the flange-shaped portion between a circular bottom pattern tool and a circular top pattern tool; applying recessed annular forming faces of circular rollers of plural kinds against the flange-shaped portion and sequentially pressing the flange-shaped portion projecting outwardly from the circular bottom pattern tool and said circular top pattern tool in a radially inward direction, thereby sequentially thickening a rear side of the flange-shaped portion; and forming the thickened flange-shaped portion into a cylindrical shape which is concentric with the base plate, thereby forming the thickened annular peripheral wall; wherein the flange-shaped portion is inclined relative to the base plate during the forming step; and wherein the inclination changes as the flange-shaped portion is sequentially pressed by the circular rollers.