METHOD OF MOLDING CYLINDRICAL PORTION OF CENTRAL BORE-CARRYING SHEET METAL

摘要

A method of molding a cylindrical portion of a central bore-carrying sheet metal according to the present invention is used when a cylindrical portion at an outer circumferential region of a base part of a boss-carrying sheet metal is molded by pressing the cylindrical portion by a molding roller while retaining the sheet metal on a rotary mold and turning the sheet metal with the rotary mold. According to the cylindrical portion molding method of the present invention, the pressing force applied to the cylindrical portion of the sheet metal by the molding roller is received by a locking portion of the rotary mold, which is engaged with a portion to be locked provided on the base part of the sheet metal, via the same portion to be locked. Therefore, the boss of the sheet metal, which is fitted at its shaft portion in a shaft portion of the rotary mold, is not forcibly pressed against the shaft portion of the rotary mold, and the precision, prior to the cylindrical portion molding operation, of the shape and size of the central bore is maintained even after the cylindrical portion molding operation has finished.