Forming of materials by extrusion

Apparatus for the forming of materials by extrusion, such apparatus comprising a wheel member with an endless groove in its periphery, a second member fixed relative to said wheel member and cooperating with the wheel member to define an elongate passageway therebetween for receiving at its inlet end material to be extruded at its extrusion end, means for rotating the wheel member in the direction of the passageway from inlet end to extrusion end, an abutment member fixed relative to the wheel member and projecting into the passageway at the extrusion end for blocking it, means defining at least one die orifice in the extrusion end of the passageway and leading therefrom, the material to be extruded being moved towards the die orifice means by frictional engagement with the walls of the endless groove constituting the major part of the passageway, characterised by the provision of means for prestressing the material constituting at least the walls of the endless groove of said wheel member, such means comprising means for preloading the wheel member via cooperating taper surfaces, of which said wheel member includes at least two, for superimposing a circumferential compression in the wheel member.