| 摘要 |
<p>A throwaway tip (31) wherein two main surfaces (32, 33) are substantially polygonal and a cutting edge (42, 43, 44, 45, 49, 50) in the form of a curved line projecting inward in the direction of the thickness of the tip is formed on at least one end edge defined between nose portions (38, 39, 40, 41) positioned at apexes of the polygon. The main surface formed with the cutting edge has a flat portion (47) in the middle, and between the flat portion and the cutting edge there is a rake surface (51) which is concave as seen in sectional view taken in a direction at right angles to the cutting edge. A surface (53) connecting the lowermost portion (52) of the rake surface to the flat portion and having a chip breaking function is formed with a plurality of projections (55) arranged along the direction in which the cutting edge extends. Each nose portion is formed with a nose protecting surface (38a, 39a, 40a, 41a) extending parallel to the flat portion inward from the end edge defined between lateral suface (34, 35, 36, 37) and the main surface. </p> |
