Rounded cutting insert

Apparatus comprising a holder and a cutting insert mounted in said holder, said holder forming a pocket having a bottom support surface and a side support surface extending from said bottom support surface, and a rotary adjustment member having a drive part communication with said pocket, said cutting insert comprising an upper chip surface, a bottom surface disposed opposite said upper chip surface, and a side surface extending between said upper chip surface and said bottom surface, said bottom surface supported by said bottom support surface, said side surface including a curved first portion of constant radius with reference to a center axis of said insert extending perpendicular to said upper chip surface, said first portion extending about three-fourths of a circumference of said insert and engaging said side support surface, said first portion including a driven part engaging said drive part so that rotation of said adjustment member produces rotation of said insert about said center axis, said side surface of said insert further including second and third portions extending from respective ends of said first portion and converging toward one another at a substantially ninety degree angle, and a fourth portion disposed between said second and third portions and oriented at an obtuse angle with respect to each of second and third portions, said second and fourth portions intersecting said upper chip surface to form therewith main and secondary cutting edges, respectively.