A method for correcting a non-rigid thin-walled tubular element (tube) of a polymeric material, where said tube has a diameter and a length, where said tube has finite geometric deficiencies and asperities, comprising:
- heat-treating said tube within a close-fitting cylindrical steel rounding-fixture, wherein the heat-treating is provided at several degrees above the glass transition temperature of the principle material of said tube and over a period of several days to minimize cross-sectional ellipticity, followed by cooling said tube to several degrees below the glass transition temperature, which freezes-in cylindricity;
- affixing a conformal lathe steady-rest, the conformal lathe steady-rest includes a steady-rest with a counter bored center hole and a plurality of radial struts extending inward and radially through radially-oriented slots in a body proper of the steady-rest, wherein each radial strut can move radially inward or outward, a conformal scroll plate positioned coaxially aligned to the counter bored center hole of the steady-rest, wherein said conformal scroll plate has a center opening for the tube and a plurality of circumferentially spaced cam-slots, wherein each of the cam-slots have an intersecting slidable pin that is perpendicularly affixed to a radial strut;
- rotating the scroll plate, causing all rollers to move radially inward as determine by the intersecting slidable pins in the plurality of circumferentially spaced cam-slots, wherein the rollers are positioned circumferentially about equidistantly around the conformal scroll plate, and there are enough rollers to support the tube therein maintaining cylindricity and providing equal and opposing support for the thin-wall of the tube as it is machined;
- equipping an end of said tube with a stiffening outer sleeve as needed, wherein the stiffening outer sleeve is a close-fitting cylindrical steel axial cup to prevent damage to said tube when fastened in the jaws of the lathe chuck;
- mounting said tube in the close-fitting cylindrical steel axial cup and through the conformal lathe steady-rest;
- commencing lathe headstock rotation of said tube and gradually increasing speed, therein ultimately causing each of the rollers to come into contact with an outer surface of said tube, therein causing all the rollers to roll, wherein the contact imparts force against the thin-wall of said tube resulting in cylindricity of said tube while it is being turned in the conformal lathe steady-rest;
- positioning a cutting tool on an inside edge of a forward end wall of said tube at a point fully supported by at least one of the rollers in contact with an opposing position on the outer surface of said tube,
- using the cutting tool to cut, incrementally, as needed, a fractional thickness of the forward end wall of said tube, so that the wall has a uniform thickness, and therefore a uniform inside diameter;
- therein creating a mating interface surface for forming a labyrinth-joint when said tube is adhesively joined to a machined circular planar closure element, wherein the machined circular planar closure element is a disk having an outer diameter that is about equal to the outside diameter of said tube, and having an inner concentric smaller diameter that is only slightly smaller than the uniform inside diameter of said tube;
- and
- reversing said tube in the lathe and trimming an aft end wall, squaring it off so that the aft end wall of said tube is cylindrical and planar, wherein it has an aft O-ring sealing surface.