KQZ you are correct. Standard process for building a crank would be to machine the part and then heat treat. Rework usually requires normalizing the part, reworking, machining and then heat treating. For a crank the heat treating is accomplished just prior to finish grinding the journals.
Cranks are made of a ductile iron which suggests a soft material. After rough machining they are usually nitriled to case harden the areas of the main and crank journals, then finish ground. Quite often if you carefully cut through the case hardening you can rework the base material which in this case should work.