| 摘要 |
PURPOSE: To provide a hard metallic rod or ceramic rod in which a helical inner bore is formed so as to be exact and uniform in pitch over the rod length. CONSTITUTION: When producing the hard metallic rod or ceramic rod which has a smooth outer surface substantially free of elevations and depressions and the helical inner bore, an extrusion molding material 9 is energized with revolving movement or twisting movement which operates uniformly over the cross-section of the extrusion molding in the form of a billet by a spinner 8 located inside the material stream, so that the material 9 is extruded to the atmosphere through a duct 4 which is subsequently connected to a nozzle with twisting, without twisting or almost without twisting. At this time, a thread-like material accompanying the revolving movement or twisting movement is penetrated or forced into the material stream in order to form the inner bore 16, and thus, the hard metallic rod or ceramic rod is produced. |
