Method for producing a rifled tube

A production method for producing a rifled tube comprising:

• a step of preparing a steel tube having a tensile strength of not more than 600 MPa, and
• a step of producing the rifled tube including a plurality of first helical ribs on the inner surface of the rifled tube and having an outer diameter of not more than 34 mm by performing cold drawing on the steel tube by using a plug which includes a plurality of helical grooves and a plurality of second helical ribs each located between adjacent helical grooves, the plug satisfying Formulae (1) and (2):
• 0.08<W×(A−B)×N/(2π×A)<0.26 (1)
• 0.83<S×(A−B)×N/(2×M)<2.0 (2)
• where, in Formulae (1) and (2), W is substituted by a width (mm) of a groove bottom surface of the helical groove in a cross section perpendicular to a central axis of the plug;
• A by a maximum diameter (mm) of the plug;
• B by a minimum diameter (mm) of the plug in the same cross section as that of the maximum diameter;
• N by a number of the second helical ribs in the cross-section;
• S by the width (mm) of the groove bottom surface of the helical groove in a longitudinal section parallel with the central axis of the plug;
• and M by a pitch (mm) of adjacent second helical ribs in the longitudinal section.