Cutting insert

A cutting tool comprising a cutting insert comprising an elongated body portion of substantially rectangular cross-sectional shape having a longitudinal plane of symmetry and having a base surface extending along the entire length of the insert and an upper surface extending along a central portion of the insert and front, rear and side planar surfaces;

• said insert being further provided with first and second oppositely directed end portions formed integrally with the body portion and respectively extending between either end of the upper surface and the adjacent front and rear surfaces;
• said first end portion having a first rake surface inclined in a first sense with respect to said plane of symmetry;
• a first front relief flank constituted by said first planar surface;
• a first pair of side relief flanks angularly disposed with respect to said side planar surfaces;
• a first front cutting edge defined between said first rake surface and said front relief flank and a first pair of side cutting edges respectively defined between said first rake surface and said side relief flanks;
• said second end portion having a second rake surface inclined in an opposite sense with respect to said plane of symmetry;
• a second relief flank constituted by said rear planar surface;
• a second pair of side relief flanks angularly disposed with respect to said planar surfaces;
• a second front cutting edge defined between said second rake surface and said second front relief flank and a second pair of side cutting edges respectively defined between said second rake surface and said second side relief flank;
• the first and second pairs of side flank surfaces tapering by amounts and in directions so as to provide clearance between the side relief flank surfaces and the side walls of the groove being cut;
• said upper and lower surfaces being formed with engaging means symmetrical about said plane of symmetry;
• a normal to the mid-point of the first front cutting edge being inclined in a first sense with respect to the plane of symmetry by an angle .alpha. and a normal to the mid-point of the second front cutting edge being inclined in a second and opposite sense with respect to the plane of symmetry by an angle .alpha. whereby the first and second front cutting edges are inclined with respect to each by an angle 2.alpha.;
• and a tool holder having a pair of clamping jaws defining between them an insert retaining slot;
• opposite surfaces of said jaws being formed with engaging means designed to mate with an engaging means formed in the upper and lower surfaces of the insert;
• said jaws being curved so as to allow their accommodation in a circular groove, said insert being held in said retaining slot with a leading front cutting edge located normally with respect to a longitudinal axis of the tool holder.