Cutting plate with chip breakers

Claim 1

A cutting plate adapted to be connected to the body of a tool for machining metal pieces, said plate having an upper surface having a generally planar face portion, a plurality of planar sides generally normal to said upper generally planar face portion, said sides joining each other in at least a rounded cutting point having a cutting edge at a cutting edge plane which is generally parallel to, and below, the upper generally planar face portion, a chip breaker groove in the upper surface defined by a downwardly inwardly declining first planar surface extending from adjacent the cutting edge to a rounded fillet and then extending upwardly as a chip breaker surface that terminates at a level above said cutting edge plane as a central planar chip breaker island portion of said upper generally planar face portion, said downwardly declining surface being planar all along the cutting edge of the planar sides and conical adjacent the rounded cutting point planes at a first angle constant to said cutting edge plane, said upwardly extending chip breaker surface defining a second angle with said cutting edge plane, which second angle is constant, a lowest point in the rounded fillet being located in a plane normal to the cutting edge plane of the cutting point and bisecting the cutting point and the depth of the fillet at the bisecting plane being greater than the depth of the fillet at a point other than at said bisecting plane.