| 摘要 |
PURPOSE: To curl a cutting chip into a coil shape so as to prevent extending the cutting chip entangled by forming irregularity, presenting a streaky shape toward a rake face from a boss surface to form a saw tooth shape in a plane view, in a tilted surface. CONSTITUTION: A step difference formed of a tilted surface 8 is provided between a boss surface 5 and a rake face 7, but this tilted surface 8 is formed not a simple plane but an irregular surface of presenting a streak shape from the boss surface toward the scrap face 7, to draw a pattern of saw tooth shape in a plane view. By action of a saw tooth tilt angleαformed by a tilted surface 8a corresponding to a cutting edge 6a and by a perpendicular 10 of a screw axial line, a cutting chip is discharged from the cutting edge 6a, to flow out on the rake face 7 in a direction almost orthogonal to this cutting edge, brought into contact with the tilted surface 8a and deformed. This deformation is such that the chip is receiving bending in a lateral direction.
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