surface 24 of the nozzle body 3 is assigned a concave surface which is formed on the clamping nut 1 this embodiment provides a very good surface contact in addition use can be made of smaller radii which can be more easily checked during the manufacturing the nozzle body 3 is designed corresponding to the nozzle body 3 from fig1 except for the shape of the second bearing surface 10 and the shape of the clamping nut 1 identical parts are provided with the same reference numbers the clamping nut 1 merges from a ring part 8 into a sleeve part 7 in a transitional region 26 the transitional region is designed in the form of an inner conical surface 9 so that the wall of the clamping nut 1 on the ring part 8 continuously decreases in size as far as the sleeve part 7 since the clamping nut 1 is essentially in the form of a sleeve the diameter of the inner recess of the clamping nut 1 has a smaller value in the region of the ring part 8 than the diameter of the inner recess of the clamping nut 1 in the region of the sleeve part 7 the nozzle body 3 and the housing 2 are placed into the inner recess of the clamping nut 1 it is essential that there is at least one curved bearing surface in a surface pairing between the clamping nut 1 and the nozzle body 3 so that a relatively wide.