| 摘要 |
PURPOSE:To prevent the clogging of chips while providing a larger margin for grinding by forming a conical guide part on the end of a cylindrical body and spirally forming a rake face on a part of the outer peripheral surface of said body and guide part. CONSTITUTION:A conical guide part 1 is continuously molded on the end of a cylindrical body part 5, and a rake face 6 is spirally molded from the tip of the guide part 1 to the side face of the body part 5. A cutting edge 7 is formed by a ridge line between the rake face 6 and the guide face 1. A cylindrical shank 8 is also continuously provided on the rear end face of the body part 5. A drill thus constructed is rotated, with the shank 8 being held by a chuck, and the guide face 1 is brought in contact with the end face of the hole 3 of a workpiece 9, preventing the runout of the drill. The end face of the hole 3 is cut by means of the cutting edge 7, allowing chips 5 to escape toward the side of the body 5, along the rake face 6. |
