Since the invention of the auger‐type extrusion machine, there has developed a large business devoted to the production of extrusion machines of various types and sizes for the ceramic industry. During this time, a vast body of empirical knowledge concerning the design of augers, dies, and machines to do particular jobs has grown. As of today, no method has been proposed by which values may be assigned to the design parameters of an auger so that there may be reasonable assurance that it will extrude a material, the plastic properties of which may be known. This paper proposes a model for the operation of an auger on a material and adapts the theory of the screw conveying of solids in organic thermoplastic extrusion machines to the study of this model. The concept of the characteristic function, which describes the action of a particular extruder on a plastic material, is discusse