the rotation of the peripheral thread 23 also gives the chips a push in the angular direction due to the friction between the peripheral thread 23 and the chips further as indicated above due to the relatively high rotating speed of the peripheral thread 23 the chips will be exposed to centrifugal forces that will keep them in close contact with the inside of the cylindrical pipe 19 in accordance with the present invention the feed screw 18 includes an angled end part 22 for releasing the chips in the radial direction towards the peripheral grinding zone the angled end part 22 is angled so as to redirect the chips which are conveyed in a mainly axial direction inside the cylindrical pipe 19 to a partly radial direction towards the grinding zone as they exit the cylindrical pipe this is achieved in that the angled end part 22 is arranged at an angle with respect to the peripheral thread 23 the re directing of the chips is not such that the chips will be re directed so as to be conveyed in the radial direction only namely the chips have an inherent kinetic energy in both the axial and the angular direction as they reach the angled end part 22 and this kinetic energy will not be totally lost part of the axial angular kinetic energy will however be transferred into kinetic energy in the radial direction.