separating air inlet 11 enters the guide blade ring 8 in the annular space between the guide ring 5 and the housing wall and is deflected there into a corresponding counter flow between the guide ring 5 and the separator wheel in order to enter the flow channels between the blades of the separator wheel from the outside with the material to be separated which was introduced via the inlet 10 for material to be separated and the separation into fine material and coarse material takes place in the flow channels the separating air with fine material leaves the separator via the outlet 6 the coarse material is rejected in the inlet area of the flow channels between the blades of the separator wheel by the centrifugal force and it is brought into the range of action of the mill through the annular space between the guide ring 5 and the separator wheel the structural association of the cover disk 7 enclosing the diaphragm with the separator wheel is assumed in the embodiment according to the top part of fig1 it should be pointed out that this cover disk 7 with the adjustable diaphragm may also be separated from the separator wheel and be associated with the housing 13 especially the cover 9 this solution may be advantageous because the cover disk 7 with the diaphragm may have a heavier weight compared with simpler cover disks and no additional drive energy is necessary for this heavier weight if the cover disk is separated from the separator wheel and is associated with the housing in summary the present invention can be defined in that two preferred solutions are shown for the problem of varying the cut point.