You would need to reharden the spring only if you heated it or some of it above tempering temperature (say, 600 F°/blue surface heat oxide color). If not, the previous heat treat will be unaffected by your work. Did you polish the worked area to 400 grit or finer? All polishing with the long axis of the spring?

Last edited by Rocketman; 11/11/08 01:31 PM.