Thursday, August 13, 2009

Grinding Marbles into Submission

I make hand-blown glass marbles, which I've blogged a little bit about previously. I'm pretty good at it, but in order to be GREAT, you have to make quite a few. Unfortunately, I don't have the energy or time to practice enough to be great, so I'll settle for good enough. Sometimes I make a marble that is great in it's color, pattern, or something that says this one could have been great, but it isn't quite round or has some "skudge" on the surface. That's where cold working the marble comes into play.

A marble, to be great in my mind, not only has to have a great interior, but also be perfectly spherical. A marble is just a fancy name for glass sphere! I priced out sphere polishing machines that are normally used in lapidary (stone and gem) working. $2000 and up just isn't in my price range. Therefore I do what I usually do, figure that I can make one myself. How hard could it be? A few hours on the net and I saw that others had done similar things. I took the best of what I found, thought about it, and then proceeded to design my own. The video below shows the results.

I was absolutely astonished that it works. I really was a disbeliever in myself. This is less than $50 in parts. The only thing I bought were surplus gear motors at $7 each. The rest of the stuff I had around the workshop. I had the hinges, some extra T-Track, and the on/off switch. I've purchased a collection of pipe fittings and couplers from the big box hardware aisle. There is a whole story that can (and will) be written about what I've learned. The grit feed is absolutely genius. I didn't invent it, but think I've taken a couple of things I saw and incorporated it into a better approach. The grit is suspended in anti-freeze rather than water. This does two things, first it makes the solution more viscous and the grit doesn't come out of solution and sink to the bottom of the cup. Second, water would make parts rust, not good.

I've done a lot of testing, and the results are spectacular. The first marble I did was an early clear sphere that clearly wasn't a sphere. It was pretty squished. Ten minutes at 80 grit and the thing was perfectly round. Un-freaking-believable. It's pretty messy, but cold working glass usually is.

Someday I'll take a series of before, during, after pictures to post. If I could only remember to do it.


  1. Jeff, this is really tremendous. I can think of a LOT of applications for it...Brilliant.

  2. That's awesome! Can you post plans?

  3. There are no plans. I made it up as I went along. There are some smaller machines for small marbles that people have made. Also, see rock grinding machines that can do this size and larger. This one follows similar principles but those machines start out at over $2000 and take quite a bit of space.