| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill tool capable of applying high local pressure to a cutting edge to show a boring efficiency and sufficiently discharge frictional cut materials even in the case of larger diameter, and reducing stress to fix the cutting edge to the hard metal without damage even in the case of striking a reinforcement bar. SOLUTION: This drill tool having an entire hard metal head 1 is constituted by two sets of cutting edges formed by a main cutting edge 2 and an auxiliary cutting edge 3, and the main cutting edges 2 and the auxiliary cutting edges 3 are disposed not to intersect perpendicularly to each other. In this drill tool, the auxiliary cutting edges 3 are disposed to form an angleαwith the main cutting edges 2 are disposed preceding to the main cutting edges 2 with respect to the rotating directionωto make the angle between the main cutting edge 2 and the auxiliary cutting edge 3 ranging from 40 to 90 deg., preferably recessed parts 4, 5 recessed in the radial direction are provided between two adjacent cutting edges 2, 3.
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