| 摘要 |
PROBLEM TO BE SOLVED: To provide a throw-away tip to considerably improve the finished surface roughness by suppressing the chattering vibration. SOLUTION: A substantially arc-like flat drag 7 is formed between a nose part 6 and a main cutting blade 4 provided on an acute corner part D. The radius R of the flat drag 7 is set to be in a range of 3.5r to 10r where r is the radius of the nose part 6. The length of the chord to connect both ends P-A of the flat drag 7 is set to be in a range of 0.2 mm to 2.0 mm. Lands 10a and 10b are formed on the nose part 6 and the flat drag 7, respectively, and the land angleβof the flat drag 7 is set to be larger than the land angleαof the nose part 6. A first projecting portion 14 having a peninsula portion 14b extending to the nose part 6 is formed on an upper surface 2 forming a cutting face of the tip 1, and the minimum distance from the first projecting portion 14 to the main cutting blade 4 is set to be 1 mm, and an erection surface 16 of the first projecting portion 14 erected from a bottom surface 11 is set to be within a range of 15 deg. to 50 deg..
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