Gunner wrote:
On Fri, 20 May 2005 16:26:31 +0000 (UTC), Christopher Tidy
wrote:


I woke up in the night and it occurred to me that a stone
polisher (or rock tumbler as some people call them) would
make a great home shop project.

I figure I can make a drum (probably cube-shaped) from
welded 1/4" plate. The drive is going to be more of a
challenge (I don't have a great deal of cash to spend on
this).

I remember seeing plans for a DIY rock tumbler many, many years ago in my
childhood subscription to Popular Mechanics. But there's a huge price
difference between consumer commodity products of back then and of today. I
strongly suspect that you could buy a decent-quality used one off Ebay (or a
cheap new one for $20 from Harbor Freight) for the same amount of money --
or less -- than building one yourself (by the time you factor in the costs
of all the materials, parts, and fasteners -- not to mention your time and
labor). Unless you are really looking for a new home project to undertake.

If you do decide to build one yourself, you won't want to make the drum out
of steel (or any other metal) and you certainly don't want it to be a cube:

1. Steel is too hard and would cause the stones to fracture and scratch.
2. Aluminum also would not provide enough cushioning (and might get embedded
with abrasive).
3. Even if breaking and scratching is not an issue, a metal drum would be
very noisy.
4. A cube shape is too "angular" a geometry: the stones would tumble too
violently and fracture or scratch.

Ideally, what you want is a rubber drum that has an octagonal profile. The
stones should be rolling and sliding against each other (not dropping and
crashing), with the octagonal sides providing just enough tumbling action.
If you must make a drum out of metal, you'll probably want to glue rubber
sheet all over the inside. (Of course, then you have to worry about abrasive
getting trapped in the seams. Remember, you will need to progress from
course to medium to fine to polish.)

Even if I were going to make my own tumbler base station, I'd probably still
buy the hard rubber drum.

Btw, tumblers can also be used for deburring, derusting, and cleaning small
metal parts.

Thanks for suggesting eBay. I just had a look at a few machines on
there. The way in which the drum is supported on smaller rollers solves
the gearing problem rather neatly.

Chris


A local gentleman uses a 55 gallon drum with flanges welded inside to
provide a tumbling action, sprayed with bed liner for longevity. He
has it attached to the counterweight arms of a pumping unit here in
the oil fields. He can tumble a **** load of rocks at one time, for
little or no money G

Rather impressive how well it works.

Nice idea. Do you have any pictures of the contraption? I'd love to see.

Chris


Ill see if he has a run going this weekend and take some pictures.

He also makes spheres using home made Stuff.

Thanks. Would be fascinating to see. What kind of spheres does he make?

Chris


He takes a chunk of rock, sorta kinda knocks the corners off with a
saw, and then turns them into highly polished spheres using a wierd
looking but really neat grinding arraingment of motorized cups and
grinding media.

Like these

http://www.therockshed.com/spheres.html

Very neat. Must have taken some ingenuity to build a machine that can
grind those.

Chris