I've been thinking about this for a long time and finally decided on building a cheap and easy caster for white metal. I've cast in two piece molds but a centrifugal caster will force the molten metal into the mold so you get much finer detail. I decide to use a small fan ( $10 from Walmart) and make the mold from 3" plumbing waste pipe. Plywood bottom with a turned center to fit into the center of the fan. It will be held on by rubber bands.