Abstract: An insert fitting for a convoluted hose end includes a generally cylindrical nipple insert having two spaced annular sealing surfaces and a relief region situated between the surfaces. The relief region has a diameter less than that of each of the sealing surfaces, each of the sealing surfaces being radially equidistant at all points from a longitudinal axis extending through the center of the insert. In the preferred form, each of the spaced sealing surfaces has a longitudinal width in the range of seventy-five to one hundred percent of the pitch width of the convoluted hose.

Abstract: Method and apparatus for continuously-developing multi-layer tubing from plural ribbons of wrapping material of indefinite length layered in seriatim upon a continuously-formed mandrel serving as a temporary supportive base for the tubing. A driven cylindrical winding mandrel is rotatable about its longitudinal axis and has a plurality of longitudinally-extending serrations on its exterior periphery. A stationary driving helix is operatively associated with the winding mandrel means for feeding a workpiece in ribbon form through the driving helix. Initial pressure means proximate the driving helix allows the continuous curling of the workpiece radially inwardly into adjacent helical convolutions about the winding mandrel. This impresses serrations on the convolutions mating with the winding mandrel serrations in the generation of the helical coil configuration and the definition of a developing formed mandrel as a supportive base.