Face milling cutting insert having convex rakes with obtusely intersecting flat surfaces

摘要

A cutting insert wherein cutting edges are formed on a pair of ridge portions of an upper surface and a pair of ridge portions on a lower surface in a staggered position relative to the ridge portions of the upper surface in a direction along the peripheries of the upper and lower surfaces. Rakes are formed on side surfaces of the insert body connecting to the cutting edges. Each rake has an inclination such as to be closer to a center of the upper or lower surface at a position remoter from the corresponding cutting edge. Each rake is formed of a curved surface which is formed along the side connecting to the cutting edge and which is curved along the peripheral direction so as to round out in an outward direction from the insert body, and a flat surface which obtusely intersects the curved surface and connect to a ridge portion opposite from the cutting edge formed along on the side of the rake. The positions and the shapes of the curved surface portions and the cutting edges are determined on the basis of the flat surfaces and the upper and lower surfaces. The insert can be prevented from shifting and the working accuracy can be improved by accurately forming the cutting edges and other portions.