(57) Apparatus for helically curling longitudinally currugated thin strip material into a flexible corrugated tube has a curling unit with driven input rollers forming a nip that matches the strip, and a cassette for a reel of the material which is connected to said unit and has strip guide rollers immediately adjacent the input rollers. The curling unit has driven output rollers on an upright support to drive the strip, and a spider which is vertically adjustable on the support and carries strip guide rollers which are on spindles equidistant from the longitudinal axis of the forming tube, and radially adjustable, so that adjustment of the spider on the support and the spindles on the spider permits the unit to form tubes of different diameters. A locking mechanism intermittently crimps overlapping parts of the forming tube. A bending device aids in forming relatively stiff strip stock, and also aids in forming softer stock into very small diameter tubes.