COUNTER BORING TOOL AND DRILLING TOOL WITH COUNTER BORING TOOL

PROBLEM TO BE SOLVED: To provide a counter boring tool capable of accurately forming a counterbore around a through hole while preventing entry of foreign matters during rotation by a simple and light structure. SOLUTION: The counter boring tool 20 is provided around a drilling tool 60, and forms a counterbore 2 having a diameter larger than the outer diameter of a through hole 3 around the through hole 3 bored on a wall panel etc. by the drilling tool 60. The counter boring tool 20 is provided with a plurality of tool support parts 22 fixed on the outer peripheral face of the drilling tool 60; cutting tools 24 for counter boring fixed to the tool support parts 22; and foreign matter removing parts 26 interposed between the tool support parts 22 and suppressing entry of foreign matters between the tool support parts 22. On at least part of the tool support parts 22, through holes 28 for fixation to which fixation screws 30 for fixing the tool support parts 22 to the outer peripheral face of the drilling tool 60 are insertable are provided, and the thickness dimension of the foreign matter removing part 26 is set smaller than that of the tool support part 22. COPYRIGHT: (C)2008,JPO&INPIT