Patent ID: 6851492
Filing Date: 2005-02-08
Classification: B23B,F16B,Y10T

Abstract:
1. A drill bit which is installed at a rotating portion of a drilling machine and finishes an undercut type hole by enlarging a portion near a hole bottom portion into a taper shape when a straight hole is drilled to a structure of a drill object by a rotating motion of the drill bit and when a depth of the drilled hole reaches a predetermined depth, the drill bit for working an undercut hole being characterized to comprise a cutter body providing at least a cutter blade for straight hole working at its tip end, a cutter blade for undercut working that is installed at a tip end portion of the cutter body so as to be swingable and projectable in the diametrical direction and that enlarges a portion near a hole bottom portion of a straight hole into a taper shape by projecting into the diametrical direction through swinging motion, a stopper sleeve that is installed to the cutter body so as to be relatively rotatable and relatively movable in the axial direction and that is contacted with a structure when a drilled depth of a straight hole to the structure becomes a predetermined depth, a shank body supporting the cutter body so as not to be relatively rotatable, a cutter blade control means for projecting the cutter blade for undercut working into an enlarged direction of the cutter body according to a relative displacement in the axial direction between the cutter body and the stopper sleeve when the stopper sleeve is further pressed after the stopper sleeve is contacted with the structure, wherein