tumbling gold castings
by tony garbutt
I would like to know if a vibratery tumbler can remove casting lines from gold. I have used green plastic pyramids with a small amount of water for 20 hours without any change. I use a small gyroc tumbler. Any suggestions would be great.
I haven't worked with gold castings for quite a few years now and never in a large production. As I remember, casting lines or major unwanted surface textures are best removed the old-fashioned way - by hand, one piece at a time. But that's not practical when numerous pieces are in need of finishing.
For minor flaws, try using a light weight plastic media that has a fine grade cutting compound such as aluminum oxide, silicates or with corborundum impregnated into it with a vibratory tumbler. This gives you a fairly smooth piece ready for your rouge work. Vibratory tumblers work much faster for this type of job than the rotary kind and remove many minor surface flaws, leaving the pieces with a dullish finish while preserving the details. The process takes a while (7-8 hours average), but not very much metal is removed and you can prepare a number pieces at one time for final finish work.
However, it seems that larger flaws such as more prominent casting lines must still be removed by other more tedious methods such as sanding, sandblasting, grinding, etc. (sigh) Since you're working in gold, metal recovery is fairly easy with the vibratory-style tumblers. Stuller Corp. (www.stuller.com) may have a better solution for your casting problem.
I hope you find a successful solution and perhaps some of the readers here who have more current experience in production casting in gold, might have some great ideas!