Casting replacement knobs and trim pieces for an old appliance or car

A broken original and one good one is all you need. Make a one-piece block mold of the good knob (pour spout at the back where the D-shaft hole is). Cast in black polyurethane resin with a brass insert set in the mold before pouring if the shaft hole needs strength. Sand, paint with vinyl dye or SEM trim paint, clear coat. Four knobs took an evening and $10, and the shop wanted $45 each for NOS.

For chrome-look parts: cast, prime, then spray-chrome or use chrome vinyl wrap. Real chrome plating on resin is not practical at home.