A good friend of mine is rebuilding a 1913 Overland. He's run into a
problem with a bronze spring. It was part of an assembly that included a
shaft and cast iron wing nut. He used heat to tackle the frozen wing nut
and has annealed part of the spring.

He's wondering on how to harden/temper it back.

I suggested he anneal the entire spring, beyond that, I've not much to
tell him. Any ideas?