PRODUCTION OF POLYGONAL METALLIC PIPE WITH BULGING PART ON OUTER FACE

摘要

PURPOSE:To produce with good working efficiency easily the polygonal metallic pipe with bulging part on the outer face of high accuracy by cutting the polygonal outer face by leaving the part corresponding to the bulging part after inserting a core into the polygonal extract pipe having the section equivalent to the bulging part section in case of the production of the polygonal metallic pipe with outer face bulging part. CONSTITUTION:The polygonal metallic extract pipe 11 having the sectional thickness of the bulging part 31 of the target finished product pipe is produced by cold extraction. This extract pipe is firmly held by the dolly 72 of the stationary plate 71 of a holding tool 7 after subjecting to lubrication treatment 111 with the treatment by stearic acid after phosphating of the inner face of said extract pipe. The core 5 having the external shape coming into close contact with the inner face of the polygonal metallic extract pipe 11 and connecting a tension bar 6 with screws on the tip part is then fitted forcibly into the extraction pipe 11. The core 5 is then pulled out of the inner face of the extract pipe 11 by the tension bar 6 after cutting in order the polygonal outer face by a milling cutter 8 leaving the part 31 corresponding to the bulging part and the polygonal metallic pipe having the bulging part 31 is produced.