穴内面穴放電加工法の開発

（加工穴内径の拡大）

抄録

This study deals with the expansion of the inner diameter of a hole fabricated on the inside wall of another straight hole by means of electrical discharge machining. Although the authors have developed devices which can machine a hole inside another hole, the shape of the fabricated hole has been limited. Aiming to diversify the hole shape, this study has improved the device so that it can machine such a hole with a larger inner diameter. The experimental results show that such a hole of 15.4 mm in inner diameter can be fabricated on the inside wall of another straight hole of 21 mm in inner diameter. This means that the improvement can make the inner diameter expanded about 5 times. As a result, it is proven that the improved device has the ability to machine a hole with a larger inner diameter inside another hole.