Abstract: Disclosed herein is size reduction apparatus such as a granulating machine of the type for cutting plastics and the like. The granulating machine includes a chamber provided with a driven rotor having a series of cutting knives affixed on the periphery thereof. The cutting knives cooperate with stationary bed knives to comminute material fed into the cutting chamber. One or more screens are positioned in the bottom of the chamber and allow for the discharge of the material after it has been reduced to a predetermined size. A series of fluid nozzles are arranged to deliver fluid such as air under pressure into the chamber in the zone below the axis of rotation of the rotor. The air acts to effect a scrubbing of the granulator screen, improve cooling of the cutting chamber and cool the cutting knives. By such scrubbing and cooling in the area of the discharge screen heavy build up of material on top of the screen is precluded as the material is circulated and suspended.