| 摘要 |
PROBLEM TO BE SOLVED: To keep the good cutting quality of each cutting edge part and to improve the chip discharging performance and the rigidity of a tool by forming a cutting edge of each conical stage by a right twisted blade and a left twisted blade, and alternately arranging right twisted blades and left twisted blades in zigzag while longitudinally deviated from each other in the circumferential direction. SOLUTION: Right twisted blades 17 are located at a front side of each conical part 16, left twisted blades 18 are located at a rear side of each conical part, and the right twisted blades 17 and the left twisted blades alternately arranged in the circumferential direction in zigzag. The chip produced by the right twisted blades 17 is taken in a right twisted groove part 19a and flows in the blade root direction of the cutter, on the other hand, the chip produced by the left twisted blades 18 is taken in a left twisted groove part 19b and flows in the point direction of the cutter. Whereby the chips flowing at the directions opposite to each other are interfered with each other at a joining part of the groove parts 19a, 19b. The axial flowing-out force of the chip is canceled by the mutual interference, and the chip is discharged to the rear part in the feeding direction of the cutter.
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