A cutting insert for milling machining having an upper face with chip breakers, a bottom face and a plurality of side faces connecting the upper face and the bottom face and adapted to carry out cutting operations such as plane machining, side machining, slot machining, hole machining or the like comprising:
- primary cutting edges provided between the side faces and the upper face, each of the primary cutting edges having a gentle arcuate line as viewed from above and side;
- secondary cutting edges provided between the side faces and the upper face and meeting the adjacent primary cutting edges, each of the secondary cutting edges having a straight line as viewed from above and the side;
- and
- corner cutting edges lying between the primary cutting edges and the secondary cutting edges, said cutting insert further comprising:
- first clearance faces and second clearance faces continuously provided between the bottom face and the corner cutting edges;
- corner cutting edge land faces and corner cutting edge slant faces continuously provided between the corner cutting edge and the upper face;
- primary cutting edge clearance faces and secondary cutting edge clearance faces continuously provided between the second clearance faces and under the primary and secondary cutting edges;
- side clearance face provided between the primary and secondary cutting edge clearance faces and the bottom face;
- primary cutting edge land faces and primary cutting edge slant faces continuously provided between the primary cutting edges and the upper face;
- secondary cutting edge land faces and secondary cutting edge slant faces contionusly provided between the secondary cutting edges and the upper face;
- and
- chip breakers formed on the primary cutting edge slant faces, the secondary cutting edge slant faces and the corner cutting edge slant faces, wherein
- the primary cutting edge has an arcuate edge line which becomes convex toward the adjacent secondary cutting edge and becomes the most convex at the point meeting the adjacent secondary cutting edge as viewed in plan, and the primary cutting edge has an arcuate edge line which is decreased in height toward the adjacent secondary cutting edge and is most decreased in height at the point meeting the adjacent secondary cutting edge as viewed in front elevation and wherein
- the primary cutting edge has a radius of curvature within a range of 300˜1200 mm at the point meeting the secondary cutting edge as viewed in plan, and the primary cutting edge has a radius of curvature within a range of 300˜1200 mm at the point meeting the secondary cutting edge as viewed in front elevation.