To provide an improved method for manufacturing a pipe with an inner surface groove having a large lead angle of the inner surface groove using the conventional general machining method.
A smooth surface metal pipe 1 drawn through a guide roll 10 is twisted through a drawing die 11 and a rotary holder 12 rotated in the same direction as the rotating direction of a grooved plug 4. After the inner surface of the metal pipe is grooved in the positions of the grooved plug 4 and a pressing member 6, consecutively the pipe is machined through a finishing die 7. In this case, the metal pipe 1 is rotated as a rigid body to the drawing die 11 and the finishing die 7, returning torsional deformation is concentrically caused in the finishing die part 7, and subsequently the pipe is untwisted to the drawn in a stationary manner, to thereby form the pipe 15 with a spiral inner surface groove having a lead angle to which a lead angle for the returning torsional deformation is added.
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SUZUKI YOSHIO
OTANI TADAO
