| 摘要 |
PROBLEM TO BE SOLVED: To provide an inner diameter precision improving method of a work and a manufacturing method of a cam shaft advantageous in order to increase a concentricity precision between the axis that takes an outer diameter of an outer peripheral part of the work for a reference and the axis that takes an inner diameter of an inner peripheral part of the work for a reference. SOLUTION: A work 1, which has an inner peripheral part 12 and an outer peripheral part 15 demarcating a hole 10 and a groove 19 formed to the inner peripheral part 12, is obtained. By charging the work 1 into a die hole 30 of a die 3, the outer peripheral part 15 of the work 1 is restrained with the inner peripheral part 31 of the die hole 30, the inner peripheral part 2 of the work 1 is ironed by an outer peripheral part of a core rod 35. By this method, the concentricity between the axis that takes the outer diameter of the outer peripheral part 15 of the work 1 for a reference and the axis that takes the inner diameter of the inner peripheral part 12 of the work 1 for a reference is improved. In ironing, a stock of the inner peripheral part 12 of the work 1 can flow into the groove.
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