To easily and integrally form a key part in a cylinder part making a remained residual wall part the key part by pressing the inner wall part of the cylinder part of the sheet metal member integrally having the cylinder part such as the boss part formed into a cylindrical shape in the axial direction so that the prescribed place remains and removing it.
The sheet metal member 10 is placed on a receiving die 21, the whole peripheral part of the outer peripheral end surface 13 of the sheet part 12 is supported with the supporting surface 22 provided in the receiving die 21. The receiving die 21 is provided with a second die surface 23 being a horizontal receiving surface, the central part back surface of the sheet metal member 10 is supported with the second die surface 23. On the other hand, a first die surface 26 supporting the outer peripheral surface 14 of the cylinder part 11 and preventing the deformation is provide in a pressure die 25. One place of the outer peripheral part of a plunger punch 27 is made to lack, the lacked place becomes the recessed part 28 for forming the key part. The sheet metal member 10 is pressed with the pressure die 25, the plunger punch 27 is descended, and the inner wall part 18 of the sheet metal 10 is pressed in the axial direction of the cylinder part 11. Although the inner wall part 18 is made to flow downward, the residual wall part 19 is received into the recessed part 28 for forming the key part of the plunger punch 27.
HARADA KUNIHIRO
FUJII NAOKI
