| 摘要 |
PROBLEM TO BE SOLVED: To provide a production method of a metal member with a through hole of a small and long size capable of securing a precision for a formed position and straightness of the through hole well. SOLUTION: A through hole 21 is formed beforehand by drilling or backward extrusion and blanking for a metal stock having a low aspect ratio before forging. When an aspect ratio of the metal stock 20 is small, a forming precision of the through hole 21 is relatively easily secured. Reducing forging is conducted while inserting a mandrel 55 in the through hole 21. The stock 20, while being reduced in an axial cross section outer diameter and through hole inner diameter by a die hole 57 of a forging die 56, is formed to a non round shape in its outer shape corresponding to a die hole inner face. On the other hand, a through hole 21 inner face is restricted by the mandrel 55 and is formed so as to have a corresponding inner diameter. At this time, the mandrel 55 is pressed into a die hole 57 roughly in isotropy in the peripheral direction through the stock 20 not to cause deflection. As a result, a forming precision of the through hole 2 finally formed for an obtained metal member 1 is improved.
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