| 摘要 |
PROBLEM TO BE SOLVED: To provide a boring method of forming a cylindrical hole or a tap hole having a bored inner surface with a high degree of accuracy, which can prevent warping of the inner surface and separation of fine foreign object therefrom. SOLUTION: A preparation hole 2 is formed in a part 1. A ball 4 having a diameter larger than that of the preparation hole 2 and a hardness higher than that of the part 1, is pressed fitted into the preparation hole 2 so as to form a flat inner wall surface 3 in the preparation hole 2 so that warps C formed on the inner wall surface 3 and fine foreign object sticking to the same are buried into the inner wall surface 3 while other warps C or fine foreign object D are confined in the part 1 or are discharged therefrom, in order to prevent the warps C and the fine foreign object D from separating from the inner wall surface 3, thereby it is possible to prevent the occurrence of a failure of a machine or an equipment to which the part 1 is mounted, due to separation of the warps and the fine foreign object. |
