| 摘要 |
PROBLEM TO BE SOLVED: To reduce machining amount needed to the finishing by changing the shape of a skirt part generally used so as to further easily perform a forging process and further, nearly form the finished shape to a blank obtained as the forging result. SOLUTION: The blank for forming a piston is obtained by forging a mass of metal. The metal mass 18 is forged in a hollow anvil 13 by using a punch 12. At this time, a recessed part is formed in an annular zone of the metal mass with the punch and also a projection protruded from the center of a base part is formed. The punch includes an open cavity 24 formable of the projection. The projection is subsequently machined so as to include a bore suitable for receiving a hinge pin for a connecting rod. COPYRIGHT: (C)2005,JPO&NCIPI
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