Patent ID: 8459162

Claim:
A plate-shaped cutting insert with multiple alternately usable cutting edges having basically the shape of an equilateral triangle, the plate-shaped cutting insert comprising: an upwardly facing top surface; a downwardly facing bottom surface; three acute corners with a cutting edge formed at each of the acute corners; and three sides, each side defined between the cutting edges formed at two of the three acute corners and extending from said upwardly facing top surface to said downwardly facing bottom surface, wherein each of said sides being formed with a recess and at least two protrusions as seen from the top of the insert, said recess and said protrusions extending from said upwardly facing top surface to said downwardly facing bottom surface substantially along a thickness direction of the insert and being adapted to be brought into engagement with a protrusion and recesses formed on a side wall of a holder, said protrusions on each side being symmetrical with respect to a line connecting the center of said insert with the center of said each side, said multiple alternately usable cutting edges comprising three pairs of straight cutting edges extending from the respective three acute corners, each of said protrusions having an apex located inside of extensions of the respective straight cutting edges, and there are provided three or more of said protrusions, said three or more protrusions being arranged with equal pitches.