| 摘要 |
PROBLEM TO BE SOLVED: To increase the number of effective cutting blades of a cutting tool throw away tip by forming a concave portion satisfying two specific conditions regarding two adjacent ridgelines on respective top corner portion of a polygon tip. SOLUTION: In a throw away tip in which a square negative tip having respective equal side length on upper and lower surfaces is made to a basic shape and a center hole is provided, a concave portion 7 is formed on each top corner portion. Namely, the concave portion 1 inclines both end portions of two adjacent ridgelines X, Z in a predetermined width W by a predetermined angleθ. When a cross point of each line A, B extending onto an upper surface 2 with a predetermined cross angleαfrom a bent point of the respective ridgelines X, Z against the respective ridgelines X, Z is defined as a and a cross point of the end portion of the respective ridgelines X, Z and another ridgeline Y is defined as b, each one portion 2a, 2b of a surface including the respective ridgelines X, Z is dropped from a position of the respective lines A, B toward a line connecting each point a, b while it is inclined by a predetermined inclination angleθ. Thereby, all respective sides of the upper and lower surfaces can be used as a cutting blade.
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