Diameter expansion drill bit

Abstract

[Problem] To provide a diameter expansion drill bit which, in a simple structure, affords a measure of latitude as to the shape of an expanded diameter part formed thereby. [Solution] Provided is a diameter expansion drill bit (10) for diameter expansion by grinding part of a prepared hole H which has been drilled into a building frame A, the drill bit (10) being equipped with: a cutting blade part (21) having a plurality of individual cutting blade parts (22); a cutting blade retaining part (23) for holding the plurality of individual cutting blade parts (22) such that these are capable of respective sliding movement in diametrical directions; and a shank part (12) for supporting the cutting blade retaining part (23), the plurality of individual cutting blade parts (22) being arrayed in plural in the circumferential direction and in multiple tiers in the axial direction, and the plurality of individual cutting blade parts (22) in each tier undergoing sliding movement due to centrifugal force accompanying rotation, to respectively expand towards the outside in diametrical directions with respect to the cutting blade retaining part (23).

Description

technical field [0001] The present invention mainly relates to a diameter-expanding drill for expanding the diameter of a part of a pre-drilled hole obtained by drilling a building structure such as concrete. Background technique [0002] Conventionally, as such a diameter-expanding drill bit, there is known an undercut drill which is inserted into a linear pre-drilled hole obtained by piercing a building frame such as concrete, and used to expand the diameter of the innermost part of the pre-drilled hole. device (see Patent Document 1). [0003] The bottom drilling device includes: a hollow cylindrical body inserted into a pre-drilled hole; an abutment member that is positioned at the opening edge of the pre-drilled hole and supports the cylindrical body through bearings so as to be freely rotatable; A shaft that is slidably engaged with the cylinder and rotates integrally with the cylinder; a truncated conical tapered portion that is provided on the front end side of the ...

AI Technical Summary

Problems solved by technology

[0006] In the above-mentioned conventional bottom hole drilling device, the arm having the cutting edge is guided by the outer peripheral surface of the tapered part, so the tapered part has to be supported by the cylinder, and the structure becomes extremely complicated. The problem

[0007] In addition, since the arm provided with the cutting edge is moved downward and opened outward through the guide groove to grind the inner peripheral surface of the pre-drilled hole, the shape of the enlarged diameter part formed naturally create constraints

Images