MANUFACTURE OF CYLINDRICAL BODY

PURPOSE:To prevent the thickness deviation of cylindrical part of a bottomed cylindrical body in impact machining method by forming plural radial grooves on the bottom of cavity of a die or at the tip of a punch. CONSTITUTION:Material A, for instance an Al alloy disk coated with lubricant on the surface is put in the cavity 2 of a die 1, and the material A is impact pressed by actuating a punch 3. The material A is plastic deformed and flows out along the punch 3 from the gap between the inner periphery of cavity 2 of the die 1 and outer periphery of the punch 3, and forms an impact product of bottomed cylindrical form. Since plural grooves 16 are provided radially at the tip of the punch 3, flow of lubricant on the material A and this surface is made smoothly and uniformly and thickness deviation of cylindrical part is prevented. When the punch 3 goes up, inside of the impact product becomes negative pressure and a valve 10 goes down to open an air inlet, and the punch 3 comes out from the impact product 15.