Building a stone polisher

Hi all,
When I was about 8 or 9 years old I really, really wanted a stone
polisher. I think they were rather expensive and also (probably wisely)
my parents thought that I would be bored having to wait months for
results, so I didn't get one for my birthday. Anyway, 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 reckon I probably need about a
30 rpm drum speed and 50 W of power for a small polisher. But the drive
needs to be sturdy and energy efficient if I'm going to leave it running
in the shed all year. A mulit-stage belt drive will be fiddly and
probably not very energy efficient. It seems to me that the best
solution would be an oil-filled worm and wheel gearbox, but I'm not sure
where to scrounge one from. Can anyone think of pieces of industrial
equipment which use a suitable gearbox, which I could look out for in
piles of junk etc? Has anyone built one of these before? Any ideas would
be welcome.
Best wishes,
Chris
Reply to
Christopher Tidy
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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.
- Michael
Reply to
DeepDiver
Thanks for the message. It's so long since I looked into this subject that I'd forgotten about the need for abrasive. I thought you just put the stones in and let them tumble together. My idea might also be partly based on my recollection of a concrete mixer with a specially made steel drum used for smoothing and cleaning flame cut metal parts at a place where I had a summer job once. But I really did intend it as a home shop project (i.e., one in which much of the fun is to be had in the construction). I also suspect I'd get something of a rather higher quality than the consumer products, which look a little plasticky to me!
Best wishes,
Chris
Reply to
Christopher Tidy
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
Reply to
Christopher Tidy
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 shit load of rocks at one time, for little or no money
Rather impressive how well it works.
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
Reply to
Gunner
Hi Chris:
Dan Williams' pyrotechnics site:
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The ball mill is beautifully described under "tools" but there's so doggone much interesting information elsewhere that you'll want to look at everything. Giant fountains, giant sparklers, homemade balance scale, etc., etc.
Best regards -- Terry
Reply to
prfesser
Big old probably obsolete copy machines the kind it would take a few strong men to carry have some great strong gearmotors in them.
Reply to
bamboo
A couple of years ago, I bought a 3/4 HP bodine gearmotor for, like, $5. That was one heavy motor. Gave it to my friend, who used it for his meat grinder project.
Try
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8 in/lbs will probably be enough.
I am, in fact, tempted to try making a rock tumbler also.
i
Reply to
Ignoramus19969
One standard 5- or 10-gallon propane tank, empty, flushed etc Cut a square door in the side, hinge it, add a hasp or something to keep it closed. Line it with rubber sheet, held with good contact cement. The spray bedliner might also work, you can get in in aerosol cans at any parts store. Support it on a "Vee-block" of 4 inverted wheels - the stationary ones that are used with casters. 2 additional angeled wheels at the ends keep it from moving axially. Any small electric motor with a very small-diameter pulley on it. Belt runs around the outside of the tank between the door and the top (or bottom). Use a long thin flat serpentine belt. Might need a simple spring tensioner. Add rocks, carborundum power. You'd probably want to tape the door after filling to make sure you didn't leak carborundum all over the place. - - Rex Burkheimer WM Automotive Fort Worth TX
Christ> Hi all,
Reply to
Rex B
So is there a consensus about how many RPM the barrel that holds the stones (or in my case, old bolts from a project car) should be turning?
Peter
Reply to
Peter Grey
30 rpm was just my guess while I was thinking about a design this morning. Having done a little more searching online I've found two commercial models which run at 45 and 52 rpm, so this gives a rough idea.
Chris
Reply to
Christopher Tidy
I'd expect 4 - 10 RPM would be about right. Slow enough to allow sliding, fast enough to induce some tumbling. Get a variable speed motor.
- - Rex Burkheimer WM Automotive Fort Worth TX
Peter Grey wrote:
Reply to
Rex B
Some people (Rex and Gunner) talk about incredibly large (for me) rock tumblers. There just must be a reason for those rock tumblers. Do owners of these huge tumblers make any sort of money from the polished rocks?
i
Reply to
Ignoramus19969
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Great stuff. I haven't ordered from them in 15 years, but they were good solid people the last time I dealt with them.
Reply to
Tim Wescott
Ill see if he has a run going this weekend and take some pictures.
He also makes spheres using home made Stuff.
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
Reply to
Gunner
There is probably an ideal FPM range, just like metal removal. Might depend on the type of rock, so variable speed might be desirable.
Reply to
Rex B
Ok...from scratch and h1) round is better. The goal is a rolling motion with very little actual sliding as the sliding causes flat spots. Rather than speed itself being the most critical (other than running so fast that they don't tumble), load is more important. For example, a drum 1/8 full may not tumble at all (will slide) but the same speed and tub will tumble perfectly when half full of rocks.
2) Start with the harbor freight cheepie..at 20 bucks for your first try it's a cheap way to find out if you hate waiting it or not.
3) Part of tumbling is critically choosing the stones to charge the machine with. You want a load that is all roughly the same hardness. Also, youwant a mix of sizes from large to small rather than mostly unifrom sizes. All large or all small will not polish well as surface contact between the pieces is reduced.
4) Because you will be going through at least 4 grit sizes (5 for some), clenliness is CRITICAL. If even one piece of coarse grit makes it through to the finer stages you may have to start all over to get a goood polish. The best solution is to have different drums for each grit. Of course, you have to meticulously wash the stone load when changing grits.
5) harbor freight does sell grit but you can probably get it cheaper in greater bulk (5 pound containers) if you are really interested. When you get to the polish stage, you'll also need plastic pellets to add to the mix. These are readily available and really improve the polish time and quality. Following the last polish, most rocks benefit from a run of several days in a clean tumbler with a little borax added to the water. Oh yea....in the coarser grits, gas can build up in the drum so you either need to "burp" a closed drum or have provision for the gas to come out by itself.
6) For the impatient, a vibratory tumbler is a LOT faster. If you are actually going to invest more than a hundred bucks in the project, go with a vibratory. One nice thing about vibratories is that you can diamond saw shapes and the finished stones will maintain roughly the same shape rather than having all the "points" rounded off as a rotary tumbler does.
7) There's almost no money it...you have to do it all for the pleasure of finding "treasures". The only money is in the really good stuff like meteorites and hard rock digging that you need a saw to slab the good stuff from. You can get lucky and find some worthwhile stuff here and there but it usually takes more effort than just wandering arond picking up rocks. Richardson Ranch in central Oregon is a wonderful (pay by weight) place to go in an effort to find some "better" items. Free camping, about a buck a pound, and to the best of my memory, 15000 acres of ground with several locations of thunder eggs, agate, jasper, and other goodies already located for you to do the digging yourself. The prinevill. OR chamber of commerce also holds several mining claims for agate beds in order to kep them open free to the public and encourage tourism. Heck, basically anywhere you go there is something to be had. Many books on "sites" are available (many sites are mostly played out as it used to be a popular hobby.)
I hope this gets you started....it can be a real joy for the family to go on treasure hunts for suitable rocks. Although kids tend to not understand that granite, sandstone and some similar don't polish well (you have to find a way to tell them it's pretty for them to keep but not to polish), they still love the looking for pretties at the beach and elsewhere. Almost anywhere you go you have something to keep busy doing. Heck, I found some of the most beautiful jasper pieces as the gravel topping of the truck parking by a hotel in Ontario, OR.
If you have more questions, let me know. I aint an expert but might be able to help a bit.
Koz
Reply to
Koz

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