The roughness of the shaft is as much, or probably more of a concern than the reduction in diameter. I've just acquired the equipment for an old school repair method called "metal spray", or sometimes known as "metalizing" where a shaft is machined or ground undersize, and powdered metal is deposited onto the surface with a flame and high pressure spray, then turned back to the original size. One alloy of several types of powder I received with the kit has instructions that the final finish is hard enough that it must be ground, not machined. I'm planning to alter the diameter of crankshaft journals with the kit. Something similar could probably be done to that shaft if you can find a machine shop that does that type of work.

I spoke with a technical advisor of a company that uses the process to rebuild turbine shafts on jet engines, so it's not some kind of Mickey Mouse procedure used by shade tree wrench jockeys. He says the powder alloy they use is 95% Nickel and 5% Aluminum.
Jerry

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