Cutting insert with raised cutting edge

Claim 1

A cutting insert for chipforming machining of metal workpieces comprising a polygonal body of wear resistant material, said body including top and bottom surfaces, and a plurality of peripheral walls extending therebetween, the intersection of said peripheral walls and at least said top surface forming cutting edge means, said top surface including: a land area joining said cutting edge means and extending inwardly therefrom toward a center of said body, said land area including: corner portions disposed at respective corners of said body, a recessed portion disposed between adjacent corner portion at a lower elevation than said corner portions, said recessed portion lying parallel to said corner portions, and sloping portions inclined downwardly from said corner portions to said recessed portion, descending surface means joining an inner margin of said land area and descending therefrom toward said center of said body, primary projections disposed in said descending surface means at respective corners of said body, said primary projections being convex and sloping downwardly and inwardly and each including a planar upper surface located at an elevation between an adjacent section of said cutting edge means, and secondary projections disposed in said descending surface means, said secondary projections being convex and sloping downwardly and inwardly, and each including a planar upper surface located at an elevation below an adjacent section of said cutting edge means, said secondary projections being spaced from respective ones of said primary projections in a direction toward adjacent corners of said body to define chip curling zones between said primary and secondary projections.