| 摘要 |
PROBLEM TO BE SOLVED: To provide a throwaway tip that forms chips curled with a fixed diameter and eliminates their tangle (stable chip disposal), stabilizes the direction of chip evacuation, and restrains cutting resistance. SOLUTION: The tip of a corner portion has two straight cutting edges crossing at a nose radius portion, and a breaker wall whose boundary with a rake face is inclined against the two straight cutting edges so that the distance from the tip of the nose radius portion to the boundary with the rake face is shorter on one of the two straight cutting edges than on the other. The distance from the tip of the nose radius portion to the boundary between the breaker wall and the rake face is 0.3 to 1.0 mm on a straight line that is parallel with the straight cutting edge with the shorter distance to the boundary between the breaker wall and the rake face and that intersects the tip of the nose radius portion. The breaker wall has a recessed portion receding widely to the back in the direction of chip evacuation.
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