| 摘要 |
PURPOSE: A double-wall pipe connected spirally and a double-wall pipe forming method are provided to serially connect double-wall pipes without couplings by forming a double-wall screw pipe and to improve the strength of the double-wall pipe using various reinforcing materials. CONSTITUTION: A double-wall pipe forming method comprises the steps of inner circumference processing, outer circumference processing, and cutting process. In the inner circumference processing, a female screw portion(90) having a thread pitch and a thread recess is formed by processing an inner wall of the inner circumference using an end mill. In the outer circumference processing, a male screw portion(91) having a thread pitch and a thread recess is formed by processing an outer wall using an outer circumference processing cutter. The outer surface of the male screw portion is cut by a blade of a cutting device.
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