| 摘要 |
A method of forming a cylindrical portion of a sheet metal member having a center hole, according to the present invention, comprises the steps of holding a sheet metal material having a boss portion between rotating dies, rotating the sheet metal material with the rotating dies, and pressing a cylindrical portion formed at an outer periphery of the base plate of the sheet metal material by means of a forming roller, thereby forming the cylindrical portion. In the method of forming a cylindrical portion according to the present invention, a force for pressing the cylindrical portion of the sheet metal material by the forming roller, is supported by engagements of the rotating dies engaged with engaged portions disposed on the base plate, thereby never causing a state wherein, against a rod portion of the rotating die, a boss portion of the sheet metal material fitted by the rod portion are strongly pressed, and making it possible to maintain accurately the shape and measurements of the center hole prior to forming the cylindrical portion, even after forming the cylindrical portion.
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