| 摘要 |
PURPOSE: A throwaway tip is provided to reduce damage of a corner cutting edge by starting cutting from the corner cutting edge toward the outer periphery and to improve cutting property. CONSTITUTION: One type of tip is used, outer-peripheral-side corner cutting edges of front cutting edges are projected, and rotation paths of outer peripheral cutting edges are overlapped by a plurality of tips. A tip(1) is formed in substantially the shape of a rectangular plate, and two pairs of cutting edges in an upper surface which are not parallel to each other are defined as a first and a second short cutting edges(6,7) and defined as a first and a second long cutting edges(8,9). Each of corner angles of two corner cutting edges(10,12) sandwiching the first short cutting edge(6) is set to 90 deg.C or less, a corner angle of another corner cutting edge(11) is set to 90 deg.C or less, and a corner angle of a corner cutting edge(13) is set to an obtuse angle. The second long cutting edge(9) in one of the same two tips(1) projecting toward the distal end of a tool body(21) is defined as a front cutting edge and the first short cutting edge(6) is defined as an outer peripheral cutting edge, the first short cutting edge(6) in the other one of the tips(1) is defined as a front cutting edge and the first long cutting edge(8) is defined as an outer peripheral cutting edge, and the corner cutting edges(10,12) sandwiched by these cutting edges are projected toward the outer periphery.
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