I came up with a method to clean up the thread on that tractor axle that really worked slick.
Mount axle in lathe and steady rest.
remove top brass slider bar in steady rest.
Make a replacement bar for slider out of scrap, drill one hole to bolt bar in steady rest and another for the size tap that has the same lead as the axle, I used 5/16X18. Cut this piece so the hole for the tap is just exposed.
Mount bar in steady rest with tap in bottom hole. Adjust so tap just touches threads.
Use a vice grip to prevent rotation of tap. Turn axle in steady rest by hand. Tighten steady rest, repeat.
Karl