| 摘要 |
PROBLEM TO BE SOLVED: To provide a diameter expansion drill bit which can process even a thin-diameter prepared hole with a simple structure.SOLUTION: A diameter expansion drill bit 10A which is used by being inserted into a prepared hole H perforated in a skeleton C and is for diameter-expanding a part of the prepared hole H by grinding comprises a cutting blade part 21 which grinds a part of the prepared hole H and includes an engagement hole 41 extending in an arbitrary radial direction at the shaft center part, a cutting blade holding part 22 which includes an engagement part 43 with that the cutting blade part 21 engages as movable in the radial direction through the engagement hole 41, and a shank part 23 which supports the cutting blade part 21 at the tip part through the cutting blade holding part 22. The cutting blade part 21 and the engagement part 43 are configured so that the cutting blade part 21 is moved in the radial direction by a centrifugal force accompanied with rotation and is rotated eccentrically to the shank part 23. |
