| 摘要 |
PURPOSE:To perform hole machining with excellent straightness by forming a gap between the internal peripheral face of the central hole of a tool and the external peripheral face of a rotary shaft and preventing direct transmission of deflection to the tool. CONSTITUTION:A gap is formed between the internal peripheral face of a central hole 22 of a head main body 20 and the external peripheral face of a rotary shaft, and movement of the tool and the rotary shaft in the direction of the external periphery is not restrained. Accordingly, even if the rotary shaft has a slight curve, a deflection due to said curve is not directly transmitted to the tool. Instead, the direction of a course of the tool may be guided through guidance of only a guide pat so as not to be affected otherwise, and hole machining with excellent straightness may be performed. |
