Abstract: A readily adjustable machine which continuously produces corrugated flexible metal tubing from very light gauge metal and of various diameters. A warping ring receives therewithin a longitudinally corrugated narrow strip of formable metal of light gauge and warps the same helically to produce convolutions by means of a helical warping surface which extends into one of the longitudinal corrugations. The size of the tube produced can be varied by merely substituting a warping ring of a different size. A uniquely shaped pair of die-forming rollers have lock-seam forming surfaces which are adjustable relative to each other to provide variation in the degree to which the seam will permit and withstand axial torque. The lock seam is constructed to be symmetrical about the neutral axis of the corrugation and about the slope line of the common corrugation leg of adjacent convolutions which it constitutes.