Positive rake cutting insert for use in negative rake holders

In a cutting insert adapted for forming positive back and side rake angles with the surfaces of a workpiece to be cut when said insert is mounted in a negative rake holder, wherein said cutting insert includes a body portion having substantially parallel upper and lower surfaces and peripheral side substantially perpendicular to said upper and lower surfaces, at least one channel extending from the entire outer edge of at least one planar peripheral side portion to the adjacent edge of at least one surface, said channel including an inner and an outer portion, said outer portion forming an angle less than ninety degrees with said peripheral side portion, and extending inwardly therefrom to adjoin said inner portion, said inner portion extending inwardly to adjoin said one surface at an angle greater than 90.degree., the improvement comprising:

• said inner portion and said outer portion each consisting of two substantially straight face portions intersecting at a common juncture substantially centrally located within said channel, said straight face portions of both the inner portion and the outer portion of said channel extending downwardly toward the interior of the body portion of the insert to form an angle within the range of from about 121.degree. to about 127.degree. between said conjunctive straight face portions of said inner and outer portions of said channel, respectively.