| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a base stock for pistons by which the periphery of a thinned part is prevented from breaking. Ž<P>SOLUTION: This method is intended for the method of manufacturing the base stock 1 for pistons by which the base stock 1 for the pistons is manufactured by forging, on which a skirt part 12, a pin boss part 13 and a sidewall part 14 are provided so as to project to the side of the back on the side of the back of a land part 11, a depression-like thinned parts 17 are provided on the side of the back of the land part 11 and also an outer peripheral wall part 15 is provided on the outside of the thinned part 17 in the land part 11. By preparing a die on one side for forming the surface side of the base stock 1 for pistons and a die on the other side for forming the back side and clamping the base stock for forging with the die on one side and the die on the other side, the base stock for forging is formed into the shape of the base stock 1 for pistons. A dividing line L1 for dividing the die on the other side is provided along the groove bottom of a groove part 24 for forming an outer peripheral wall part for forming the outer peripheral wall part 15. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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