| 摘要 |
Provided is a diameter-expanding drill bit with a simple structure and capable of handling even small diameter pilot holes. A diameter-expanding drill bit (10) used by inserting into a pilot hole (H) bored in a building frame (A) to expand the diameter of a portion of the pilot hole (H) by grinding. The drill bit is provided with: multiple cutting edges (21) for grinding a portion of the pilot hole (H); a cutting edge-holding section (22) for holding the multiple cutting edges (21) so that each is movable in the diameter direction; and a shank section (23) for supporting the cutting edge-holding section (22). The multiple cutting edges (21) move so as to expand radially outward with respect to the cutting edge-holding section (22) as a result of the centrifugal force associated with rotation. |
