The material to be sifted is fed into the stationary cylindrical screen by means of a screw mounted on the rotating shaft. A series of paddles which rotate inside the screen without contact, centrifugally force the material against the screen breaking up soft agglomerates. Sub-sieve material (fines) that pass through the screen discharge into a collection hopper at the base of the machine. Oversize material and hard lumps to the oversize outlet. An adjustable baffle plate regulates the flow of over size.