I formerly straightened the copper wire into “bus bars” for the astable multivibrators by whacking it with a slide hammer, but someone whose name is lost in the mists of time told me the right way to do it:
Yup, grab a piece of wire at both ends in Tiny Lathe and give it a few low-speed turns while pulling firmly on the tailstock.
No muss, no fuss, no drama, just bar-straight and slightly work-hardened copper wires:
I slide-hammered the top wire before remembering the clue. The bottom two wires have peppermint-stick swirls.
Thank you, whoever you were!