| 摘要 |
PURPOSE:To facilitate the manufacturing of an exhaust pipe by squeezing the central portion of a metallic pipe then folding around the central portion thereafter making a hole through the wall face in the central portion thus manufacturing an exhaust pipe. CONSTITUTION:The central portion 11 of a metallic pipe 10 is squeezed. Then it is bent into U-shape around the central portion 11. An exhaust hole 12 is made through the wall face at the opposite side from the folding direction in the central portion 11. The circumferential wall of the exhaust hole 12 is developed outward through burring to form an exhaust port section 13. In such a manner, two exhaust tubes 14, 15 in the upstream can be manufactured easily from a single metallic pipe.
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