Abstract: A metal cutting insert of substantially polygonal shape having top, bottom, front, rear and side faces; a front cutting edge being formed at the intersection of the top and the front face and first and second side cutting edges formed respectively at the intersections of the top and the two side faces, chip forming means being located on the top face within an area defined by the cutting edges; the top and bottom faces being respectively of convex and concave disposition.

Abstract: A cutter head releasably mounted on a tool holder and to be fitted with an exchangeable cutting insert while the tool holder is adapted to be secured to a lathe or the like; a substantially U-shaped bushing being articulatedly mounted in a recess formed in an end of the cutter head so as to define a receiver socket adapted to receive an engaging head of a drawbar longitudinally displaceable within the tool holder; the arrangement being such that with the engaging head of the drawbar located in said receiver socket, a traction force exerted on the drawbar results in transverse abutting surfaces of the bushing being displaced into a clamping abutment with corresponding transverse abutment surfaces formed on the tool holder.

Abstract: A metal cutting tool having an exchangeable cutting insert mounted on a replaceable cartridge seat releasably fitted in a tool holder of the cutting, the cartridge seat comprising a body portion with a receiving pocket formed therein, an axially directed external surface of the body portion and a substantially planar rear surface thereof; the receiving pocket being formed with a substantially planar insert receiving surface; the tool holder being formed with an insert receiving cavity having an axially directed internal surface adapted to receive the body portion and a substantially planar end surface adapted to abut said rear surface; one of said axially directed surfaces being substantially cylindrical and the other being formed with three suitably located, axially directed protrusions so that upon the screw coupling together of the cartridge seat in the receiving pocket the body portion pivots about its region of abutment so as to be clamped against the protrusions.

Abstract: A tool holder assembly for retaining a removable cutting insert on a tool holder, said assembly including a recess on the holder for receiving the insert, a side clamp juxtaposed to the insert and movable in the recess, means for positioning the insert and means for moving the clamp translationally and rotationally to clamp the insert against the insert positioning means.

Abstract: A cutting tool having a longitudinal insert comprising two opposed cutting edges that enable the position of the insert to be reused after a rotation of 180.degree. about a certain axis.