Abstract: The method disclosed consists of applying a plain tubular blank in polytetrafluorethylene to a cylindrical mandrel of a diameter providing for a clearance between said blank and mandrel corresponding to the depth of the corrugations to be formed. The blank is retained at its ends concentrically with the mandrel. A wire is then wound in a helical path around the blank under a tension ensuring the forming of helical corrugations, the blank being additionally retained at its outside surface within a zone preceding the zone wherein the corrugations are being formed. On forming the corrugations all the way along the surface of the blank, the product is heat treated at a temperature between 250 and 300.degree. C.