The cutters are separated from the striker section and is rotatable in such a way that they can swivel away from the striker section outwards in the direction of the material(15) for milling. The cutters have an inwards and outwards swivel limit which also serves as the limit for the striker piston and establishes its dead centre position. Each cutter is cut out of a plane parallel plate(17) with a protruding rotational axis(18) and protruding stop axis(19)
