The process of conventional hydrostatic extrusion limits the length of the billet that can be extruded to a length somewhat shorter than that of the chamber. Production units are also limited to pressures of about 8,000 Kg/cm2. Thus the reduction that can be affected in one pass of hydrostatic extrusion of mildly tough materials like low carbon steels or copper is limited to no more than 75% R.A., if the extrusion is performed at room temperature. For subsequent passes, each previous extrudate must be cut to suitable length so it will fit again into the chamber.

The Condie process (Austen, U.S. Pat. #3,999,415) provides the means to perform extrusion through several dies, one die at a time, in one loading of the chamber. In the present model, only two dies are loaded into the chamber together with the billet. A short length is first extruded through the first die, while the second die is kept free to move idly with the extrudate. Then extrusion through the first die ceases and the billet is forced to extrude through the second die. As the second die approaches the first die and the intermediate diameter section shortens, the extrusion stops. Thus, one cycle of a finite length is completed. But, the accumulated reduction from billet to extrudate is large, similar to the reduction obtainable by a single die from a chamber of twice as high a pressure.