Abstract: In a method for making hydraulic tubing a low carbon steel tube suitable for use as hydraulic tubing is coated on its inside surface with zinc phosphate and the outside surface is electroplated. The resulting hydraulic tubing will resist rust on the inside and on the outside during storage.

Abstract: A pipe flaring die has a central opening with a profile configured to reduce stress concentrations at the base of the flared portion of the pipe. The profile includes an annular relief area intermediate an annular gripping surface and an annular beveled portion which defines the angle of the flared portion. The relief area provides a longer transition distance for the formation of the flared portion which results in a reduced residual stress concentration created at the base of the flared portion during the forming process.

Abstract: A pipe coupling device for holding a metal pipe having a selected diameter within a range of a nominal diameter plus or minus a specified tolerance is also useful for easily determining if any pipe is within specifications. A split metal ring having a diameter equal to the nominal diameter for the metal pipe and a transverse split having a width equal to the specified tolerance is placed around the pipe. A nut having a tapered cylindrical bore having diameter such that the diameter plus twice the thickness of the split metal ring equals the nominal diameter of the metal pipe plus the specified tolerance is fitted over the split metal ring. If the pipe is undersized it will slip through the split metal ring. If the pipe is oversized the nut will not fit completely over the metal ring surrounding the pipe.

Abstract: A pipe coupling device for holding a metal pipe having a selected diameter within a range of a nominal diameter plus or minus a specified tolerance is also useful for easily determining if any pipe is within specifications. A split metal ring having a diameter equal to the nominal diameter for the metal pipe and a transverse split having a width equal to the specified tolerance is placed around the pipe. A flange having a tapered cylindrical bore having diameter such that the diameter plus twice the thickness of the split metal ring equals the nominal diameter of the metal pipe plus the specified tolerance is fitted over the split metal ring. If the pipe is undersized it will slip through the split metal ring. If the pipe is oversized the flange will not fit completely over the metal ring surrounding the pipe.