Indirect extrusion processes and apparatus

Abstract From the Canadian patent

A die holder has adjacent to its front end an annular step portion comprising a steep wall and a gradual wall tapered from the steep wall to the front end the annular, step portion being adapted to provide an annular space between the step portion and an inner surface bounding a billet receiving bore in a container when the die holder is inserted in the bore. During indirect extrusion operation foreign, impurities such as dirt, lubricant metal oxides, and the, like deposited between the bore surface and the billet are trapped and collected in the annular space against entrinment into an extruded product being formed. An annular ring partly defining the steep wall acts as a barrier that …