| 摘要 |
PROBLEM TO BE SOLVED: To conduct excellent drilling without clogging by segmenting chips in the length direction of a cutting edge to further enhance chip discharging performance. SOLUTION: An intersection P of a line X passing a thinning cutting edge part 21 and a line S passing the cutting edge 14 is set, and a line Y orthogonal to the line X and passing the intersection P is set. A distance between the line Y and a line Z parallel with the line Y and passing the groove bottom 13C of an internal wall surface 13B facing the rear side of a drill rotating direction T of a chip discharge groove 13 is set as a distance L, and the ratio of the distance L to the outer diameter of the tip side of a drill body is not less than 0.02 and not more than 0.2. COPYRIGHT: (C)2005,JPO&NCIPI
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