We used to take copper water pipe scraps and flatten em with a big sledge.
Crude but cheap. Conducts as well as anything else with the same cross section.
One nice thing about old commercial fishing boats: function is primary,
appearance is a far second. Used to make our own 100 amp 50 mv ammeter shunts
too. Just file down a piece until 10 amps gives you 5 mv voltage drop. We used
surplus meters and redid the faces with paper label and pen.
No... we didn't refine our own diesel fuel from asphalt chunks but we did throw
waste oil back in the fuel tanks and burned it. Always wondered if that was a
good idea, but the skipper said BTUs are BTUs and these ones are free.