| 摘要 |
PROBLEM TO BE SOLVED: To precisely form the external tooth and the internal tooth of a gear with a few working man-hour. SOLUTION: By dividing an upper punch 40 to an external punch 50 and an internal punch 60, by dividing so that the area ratio of an outside pressing surface to an inside pressing surface becomes from 6:4 to 4:6, further preferably it becomes about 1:1, and by pressing the outside pressing surface S1 of a stock W by the external punch 50, the stock W which is apt to flow on the outer peripheral part W1 side up to now, is made to smoothly flow on the inner peripheral part W2 side as well. Further by controlling the back pressure of the internal punch 60 to a prescribed pressure, which presses the inside pressing surface S2 of the stock W, the coming-in stock W can be properly pressed without blocking the flow of the stock W on the inner peripheral part W2 side of the stock W. Therefore the stock W can be charged by a necessary and sufficient amount to the internal tooth forming part 21 of a mandrel 20.
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