Patent ID: 7883300

Claim:
A metal cutting insert comprising: a front clearance face, an upper boundary of which defines a cutting edge, two opposing sides adjacent to the front clearance face, a pair of spaced apart, first rake surfaces extending away from said cutting edge, each of said first rake surfaces abutting on a respective side of the insert and defining, at least in part, a first chip breaking surface, wherein each of said first rake surfaces is concave and includes a first portion that descends downwardly with respect to said cutting edge and a second portion that rises upwardly and merges with a relatively short convex surface abutting on the respective side of the insert, each of said first chip breaking surfaces defined by said first rake surface and said convex surface, said first rake surfaces disposed on either side of a channel, said channel including an entry portion that commences near said cutting edge, a pair of secondary chip breaking surfaces extending away from said first chip breaking surfaces and abutting on the respective side of the insert, each of said secondary chip breaking surfaces interconnected with an associated first chip breaking surface by a transition surface abutting on the respective side of the insert, each of said secondary chip breaking surfaces rising upwardly with respect to its associated first chip breaking surface, wherein each of said second chip breaking surfaces includes an upwardly facing short concave surface abutting on the respective side of the insert that extends from said transition surface in a direction away from said cutting edge and an upwardly facing second convex surface abutting on the respective side that extends from said short concave surface in a direction away from said cutting edge, said transition surface interconnecting said convex surface with said short concave surface, wherein each of said secondary chip breaking surfaces rises upwardly with respect to the associated first chip breaking surface such that the secondary chip breaking surface is located above the first chip breaking surface and a lowermost portion of said short concave surface of said secondary chip breaking surface is located above a lowermost portion of said first rake surface, and wherein said first chip breaking surfaces impart an initial curl to a chip as the chip is cut from a rotating workpiece, while said channel causes a rigidizing of a central portion of said chip, and said secondary chip breaking surfaces impart a further curl to said chip such that a curl diameter of said chip is reduced.