| 摘要 |
PROBLEM TO BE SOLVED: To improve boring accuracy of a tool in machining a high-hardness material and the life of the tool. SOLUTION: The material quality of a tool main body 2 of a drill 1 is cemented carbide having composition of 10±2 wt.% Co-0.75±0.25 wt.% Cr2C3- remainder WC, the average particle size of WC is 0.1 to 1.0μm, and the radial rake angle of a cutting edge 8 of the tip face 7 is set to a minus angle of -5 deg. to -10 deg.. A chip discharge groove 6 having a helix angle of 5 deg. to 15 deg. is formed in the outer periphery of the tool main body 2. The groove width ratio of a land part 10 of the tool main body and the chip discharge groove 6 ranges from 0.9 to 1.1. The tip angle of the tool main body 2 is set to 125 deg. to 135 deg., and the core thickness is set to 0.38D to 0.42D taking the drill outside diameter as D. The tool main body 2 is coated with a coating layer of TiAlN. |
