in the case of a drum cutting machine in fig1 , a shaft 15 is mounted in a rotatable manner in a machine housing 16 . fastened to the shaft 15 are two rotary drums 14 , the lateral surfaces of which are provided with a multiplicity of holes 17 . the diameter of the holes 17 is selected such that cereal grains can pass straight through . the shaft 15 having the rotary drums 14 can be set into rotation via an electric motor 18 . when the machine is in operation , the rotational speed is around 50 rpm . the lower part of the two rotary drums 14 is surrounded in each case by a blade box 18 , as is shown in a perspective illustration in fig2 . the blade box 18 is composed of two structural elements 19 , to which a multiplicity of blades 20 are fastened . the structural elements 19 are arranged parallel to the two end faces of the rotary drum 14 and match the circular contour of the end faces . the blades 20 , which extend between the two structural elements 19 , are held at a small distance from the lateral surface of the rotary drum 14 . in this exemplary embodiment , the blade box 18 comprises thirty blades 20 , which are all parallel to one another and are arranged at a small distance from the lateral surface of the rotary drum 14 . altogether , the blades 20 cover approximately the lower half of the rotary drum 14 . cereal grains can be fed into the interior of the rotary drum 14 through a connecting piece 21 . the cereal grains drop into the lower part of the rotary drum under the force of gravity . by rotation of the rotary drum 14 , the cereal grains are kept in motion , so that cereal grains continuously come into the correct position and orientation in order to pass into one of the holes 17 . the cereal grains then move through the holes 17 toward the outside , until they project through the lateral surface of the rotary drum 14 . by rotation of the rotary drum 14 , the cereal grain is brought into contact with one of the blades 20 , and so a part of the cereal grain is cut off . the remaining part of the cereal grain moves further out until contact is again made with one of the blades 20 and a further part of the cereal grain is cut off . the fragments of the cereal grains are collected under the rotary drums 14 and transported away for further use . the schematic illustration in fig5 shows a detail of the rotary drum 14 having a hole 17 and also a blade 20 arranged under the rotary drum 14 . the blades 20 are set up such that the distance between the cutting edge 28 and the lateral surface of the rotary drum is as small as possible . in practice , the distance , as is indicated by the dashed line , is about 1 mm . the angle of incidence of the rear surface 27 of the blade 20 sets the extent to which the remaining cereal grain can move out of the holes 17 before it comes into contact with the next blade 20 . the greater the angle of incidence between the rear surface 27 and the tangent , indicated by a dashed line , to the rotary drum 14 , the larger the fragment of the cereal grain that is cut off by the following blade 20 . for the drum cutting machine of the exemplary embodiment , there are provided three blade boxes 18 , in the case of which the inclination angle of the blades 20 is different . in the case of the first blade box 18 , which is provided for fine cut , the inclination angle is about 4 °. in the case of the second blade box 18 , which is provided for medium cut , the inclination angle is about 7 . 5 °. in the case of the third blade box 18 , which is provided for coarse cut , the inclination angle is about 11 °. the cereal grains are cut only in the lower half of the rotary drum 14 . if a cereal grain remains in one of the holes 17 after the region of the blades 20 has been left , the cereal grain drops out of the hole 17 again and into the interior of the rotary drum 14 under the influence of gravity . in order to support this , there may be provided a needle drum , the needles of which engage in the holes 17 in order also to free stuck cereal grains from the holes 17 . as fig3 and 4 show , the structural element 19 is composed of three components , specifically of two side plates and an intermediate plate 22 arranged between the side plates . the side plates have a substantially semicircular contour which corresponds to the lateral surface of the rotary drum 14 . a blade holder for each of the blades 20 is formed in each case in the side plates , so that the side plates each form a supporting part 23 within the meaning of the invention . as is shown in an enlarged illustration in fig6 , each blade holder comprises two bearing surfaces 24 , 25 , of which one rests on the front surface 26 and one on the rear surface 27 of the blade 20 . by way of the bearing surfaces 24 , 25 , both the position of the cutting edge 28 of the blade and the orientation of the front surface 26 and the rear surface 27 are defined unambiguously . the bearing surfaces 24 , 25 do not extend as far as the cutting edge 28 but maintain a distance by way of a circular cutout . according to fig4 , the supporting parts 23 each have an undercut 30 in the radial direction . by way of the intermediate plate 22 , the supporting parts 23 are kept at a distance from one another such that an outwardly extending screw is retained at the undercuts 30 by way of its head . the screw is guided through a hole in the blade 20 and thus forms a fastening element 29 for the blade 20 . the undercuts 30 extend parallel to the contour of the supporting parts 23 , thereby forming a rail , along which the screw can be displaced . as a result , the screw can tensioned against the blade 20 in any desired position , i . e . in particular in the position defined by the bearing surfaces 24 , 25 . it thus takes a simple routine technical activity to assemble a blade box 18 from the supporting parts 23 and the appropriate number of blades 20 .