| 摘要 |
PURPOSE:To reduce the number of manufacturing processes, by forming a tip part of piping into a small diametral setting part by means of swaging and, after inserting a core bar into that part and doing cold extrusion, performing surface treatment on it. CONSTITUTION:A tip part of piping 7 is formed into a small diametral part 8 by means of swaging. Next, a core bar 9 is inserted into the inner part and cold extrusion work is carried out by a die 10. With this operation, accuracy on both inner and outer surfaces of the piping 7 is securable at a stroke. Afterward, surface grinding is performed by means of centerless grinding and then chrome plating takes place, thus a piston rod is secured. Therefore, a manufacturing process will get off with a half as compared with the conventional case, so that is comes to such one excellent in productivity.
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