We have had a magnetic tumbler in the shop for years and that thing
is spinning all day long. They are just plastic bowls with polished
steel needles in water and soap that doesn’t suds. If you take them
apart they just have a motor that spins a turntable with 3-4
magnetics glued to it. When the turntable spins it pulls the little
needles around the bowl and they burnish the items in the bowl. So
it doesn’t remove any material from the pieces in the bowl just
shines them up. You need to refinish your castings first to a rubber
wheel or emery finish before letting them spin in the tumbler. After
you take them out they are pretty shiny all over, but not high
polished so you still will need to polish them.
The advantage is that it gets into all of the little nooks and
crannies that you can’t get into easily. It really makes the job look
better. As far as Raytech, we have the medium sized unit with the
150mm bowl that is selling for about $1000 right now. It has more
features than I want but it was a good size, we will often have a
half a dozen things in there at once and you could put in more. The
digital display pooped out on us last year and we sent it in for
repair (had a one year warranty) we got it back and it’s been fine
ever since. While it was gone we bought the small version 100mm
bowl, and that didn’t work as well I didn’t think.
The only issue I had with it was that when we first got it (the
medium sized version) it came with needles that had all been clipped
to length. So the ends of the little wires were sharp instead of
rounded and polished. These didn’t burnish the pieces as well. We got
some different needles and all was good.
It works well on everything we have tried. It has yet to damage a
stone, but you need to use some common sense as to what you put in.
We have also brightened up a few chains with it. The hazard with
chains, or anything, is that the little needles become stuck in any
small hole. A rope chain for instance would be jambed full of
hundreds of sharp little needles (so I wouldn’t put it in).
You will spend a little time pulling out needles every time you take
something out of the bowl. You will need some brass or plastic
tweezers to retrieve things from the bowl as the needles are all
magnetized all would love to escape on your steel tweezers.