A metal cutting tool having an insert holder and a cutting insert releasably secured therein. The insert holder has upper and lower blocks and upper and lower jaws, each jaw projects from the front end of each respective block. The cutting tool has a cutting portion support projecting transversely from the front end of the lower clamp at an angle α. The cutting insert has a shaft and a first cutting portion projecting transversely from the shaft at the angle α. The cutting insert has non-planar abutment surfaces formed to mate with corresponding, non-planar support surfaces located on the lower and upper jaws and on the cutting portion support.