Abstract: Metal working cutting tool with a cutting insert which can be inserted in a recess of a tool shaft and fastened therein by means of a clamping jaw, whereby the cutting insert has the approximate shape of a prism with two diagonal opposite cutting edges and along one of the two lengthwise edges are adjacent cutting faces, which form an acute angle with the respective opposite principal cutting pressure and support surface, so that the angle opens towards the pressure-feed and support surface, whereby in the area of the joint lengthwise edge of the cutting face, there is incorporated in the cutting insert a continuous longitudinal groove of which one of the side walls serves as a support area for the relief-cut pressure-feed and support surface of the recess of the tool shaft, and whereas the respective other side wall forms the support surface for a recessed clamping jaw which is located in a diagonal groove of the tool shaft.