| 摘要 |
PROBLEM TO BE SOLVED: To provide a stepped drill capable of highly accurately forming a high-quality processing hole by reducing a burr height in a processing hole outlet, when applying hole drilling to a joint material composed of fiber reinforced plastic and a metallic material.SOLUTION: The stepped drill 1 comprises a small diameter part 20 for applying the hole drilling in the first place to a machinable material and a large diameter part 21 being a larger diameter than the small diameter part 20. In the stepped drill 1, a chamfer 31 is provided on a rake surface 32 of a cutting edge 5 of the small diameter part 20, and is formed so that a step angle &bgr; of the large diameter part 21 is 180°, and is formed so that a torsion angle α1 of the small diameter part 20 is smaller than a torsion angle α2 of the large diameter part 21. |
