| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill bit for diameter expansion which can cope with a small-diameter prepared hole by a simple structure.SOLUTION: A drill bit 10 for diameter expansion includes: a bit part 11 which has a plurality of individual bit parts 51 inserted into a prepared hole H and each provided with a cutting blade part 53 at a tip part of a shank part 52 and annularly arranges the plurality of individual bit parts 51; a bit holding part 12 which holds a base part of the bit part 11 so that the tips of the plurality of individual bit parts 51 can be expanded; a shaft part 13 which is detachably mounted to a power source-side rotary shaft 3a at its base end side and slidably and unrotatably mounted with the bit holding part 12 at its tip side; and an operating rod part 14 which is fixed to the shaft part 13 at its base end side and engaged with the plurality of individual bit parts 51 at its tip side, and expands the plurality of individual bit parts 51 in accordance with the relative advancement of the shaft part 13. |
