See them tumbling down,
tumble finishing those hard to clean up metal parts.
or "I'd really rather be doing something else."
. Originally published 3/9/97 last edit 01,11/2000 (set edit/find to NEW, match case, to quickly locate changes)
by Gene Olson, contributing editor with considerable help from Jerry Frost, and Barb Horton Rockwell , Nick Vincent, R. G. Aspden, Roger Olsen and others on the ArtMetal and theForge maillist discussion groups.
What is tumbling? - What can be tumbled? - Ok, so how do I go about setting up a tumbler? What is
involved? - Making it run. - It sounds like it will be awful noisy, will the neighbors call the police?
- Where do I get the media stuff to put in with the parts.
How many times have you finished making something and found that it needed cleaning up? Your
parts had sharp edges, loose scale, rust, dirt, and then it was going to need hours of sanding and
polishing in hard to get at spots to make it look like the piece you could be proud of. You wince at
the thought of rugging up in leather armor and face shield to face the wire wheel, 'cause you hate
pulling those inevitable wires out of your hide.
Well, help may be on the way. Tumbling may be the answer to your finishing problem. Especially if you have a lot of small parts to do, like handles, hinges, latches, and hooks.
"I love my tumbler and consider it a must tool for a person trying to make a living as a blacksmith."
Says Roger Olsen - from the east slope of the North Cascades.
Tumbling is a process where the parts to be finished are placed in a container and rolled or vibrated
so that they rub against each other and/or some sort of abrasive or polishing media. You put them
in, start up the turning mechanism and try and forget about them for a specified period of time, while
you get something more productive done.
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Just about anything that can slide or roll in about a third of your tumbler drum. Forged pieces,
castings, stampings, rocks, etc.
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There are a lot of ways to set up a tumbler, some are quick and dirty, and may get the job at hand
done and others are best considered if you plan to use this process over the long haul. Tumblers can
be made from pipe, old drums, cement mixers, 5 gal pails. We have an old rock tumbler that is
basically a small drum sitting on a belt driven and an idler shaft with a faceted interior in order to
cause the contents to shift as the barrel turns.
For small tumblers you may just pick them up and empty them, but on larger ones, you will want
to arrange the tumbler for ease of loading and unloading. The cement mixer type end loader is ideal
for this. Some use a side loading door on a piece of pipe or drum that is mounted high enough above
the floor to get a container under it. The following are some comments on machines that have been
built or purchased.
From: Horton@gnn.com (Barbara Horton Rockwell)
We have many tumblers. The most aggressive is a closed tumbler with doors on the side. 5 of our
tumblers are actually made from cement mixer barrels we got cheap. 5 are made from joint
compound pails, another is a "real" tumbler, hexagonal, but still rotating in cement mixer fashion.
doors for those, if needed, can be made from plywood and just fit over the end. The one mentioned
above with side doors is a pain to load and unload and to check to see when parts are ready to
remove. Dumping is a real nuisance as your dump pan must be directly under the door as it faced
the ground, and you must therefore have the tumbler high enough to allow clearance for the dump
pan. The open end ones tilt forward and dump into washtubs with homemade riddles. (Sieves that
let the finishing media fall through and catch the parts.)
From: "R. G. Aspden" <raspden@interlog.com>
I've just built a tumbler from a similar 30 gal drum. I took the bonnet off a cement mixer then
attached the drum ,cutting one end out to fit where the bonnet was located. The access door was cut
out with a touch and the interior lined with conveyor belting. The grinding medium does most of the
work not the walls of the tumbler so the belting cuts the noise and saves the tumbler walls. The door
was also lined with conveyor belting cut slightly over sized and reinserted into the door opening to
overlap with the lining. I welded two straps onto the outside of the door long enough to overlap the
drum .These had holes drilled in them to accept stud bolts welded onto the drum ,thereby allowing
the door to be bolted onto the drum. I use 3/4" knock out slugs as a grinding medium and a cement
mixer rotation ,guess 25 rpm. Noise still convinces me to go for lunch when it's running but the
results are acceptable in 20-30 minutes. The free end of the drum has a 2" pipe welded onto it and
is cradled in a bushing for support. This pipe will also accept a vacuum line when I get around to it.
On the subject of kerf of the door ,the fitting need not be tight as the scale must come out and a small
accumulation under the tumbler is acceptable to me also allows air in, when vacuum gets hooked
up.
From: erik@methow.com (Roger Olsen)
My tumbler is built out of 5/16 thick pipe 18" in diameter and 5 feet long, the door is a quarter of the drum cut out of the side but leaving 6 inches on each end for strength. it is hinged with pipe sections and rod, tight seal is obtained by welding 3/16 by 1 around the edge of the door so it overlaps onto the drum. shop vac sucks out dust, mine is set to turn at 29 rpm,(was aiming for 24 but got 29 and it seems to work great), my tumbling medium is throw aways from a punch press as well as any scraps from my saw, inside of tumbler has 4 equally spaced 3/8 by 1 and 1/4 baffles running the length to help lift and fall action. I love my tumbler and consider it a must tool for a person trying to make a living as a blacksmith.
From: frosty@customcpu.com (Frost, Jerry)
I also agree with making it an end loading tumbler, they're much easier to load and unload. You can
run it on rubber casters with a slight tilt and a single caster against the bottom end to keep it from
running off the rollers. A very simple drive mechanism is to mount the motor on a hinged board
under the drum and simply run the belt around the drum. You'll have to further reduce the rpm, if
you're running a 1728 rpm motor, either with a rheostat, phase reducer, gearing, step pulleys, etc.
With this drive setup and the casters you can make it an easy unloader too. Mount it a couple feet
off the floor with the casters behind the center of gravity, so it wants to tip naturally towards the door
end. Put the hinged motor mount under the drum, with the hinge nearest the door end of the drum.
The weight of the motor keeps it from tipping till you're ready. A simple latch or additional counter
weights will ensure the drum stays where you want it regardless of the load.
Dad was a rockhound and I grew up with rock saws, tumblers and such, in the basement or where ever they'd fit. The thread triggered memories I hadn't thought about since I was a kid. The mental image that came to mind reading the thread was of this big pyramid of 55 gl drums, nine of them I think, all turning at once, one on another, the bottom ones on rubber rollers and a funky old electric motor driving the whole mess with a belt.
Ron Reil
Barb says:
The trick in tumbling is to achieve slide. Slide occurs when the parts and the media slide from about
1/3 of the way up the side to the bottom, as opposed to being hurled partway up and falling in clumps
to the bottom. Slide protects parts and makes sure that media rather than parts contact the other
parts. when it is working right, it makes a shih, shih, shih sound. tumblers are never filled more than
1/4-1/3. Overfilling results in loss of slide, and too little media results in bashed parts. If water is
used, in the style of tumbler with a door on the side, it should cover the media about 1-2". in the
other style tumblers, only enough water to get good slide.
In our joint compound, plastic pail tumblers we use steel shot and mineral oil. those tumblers have
2"x 1.5" high wide wooden paddles mounted inside diagonally from the bottom to the open end. One
is all, I think. That works well too, they have to go really slow or they spit shot at you, and they
cannot be tilted down to empty, due to the nature of the design and the lack of weight that a plastic
bucket can support. We used covers with large shot (.080+) because of the flying shot problem but
don't need it with the tiny shot. We reach in with a homemade rake and get the oily parts out. Shot
is heavy and we don't want to dump it anyway. 3 barrels are linked together and 2 others work
together as they are small and we needed more capacity but didn't want to spend money for real
tumblers, plus we used old motors and pulley reduction devices that were laying around to make
them. Most tumblers are on timers, but some are light switch type.
Media: 4 of the 5 cement barrel tumblers use corn cob, mostly for drying water or oil from the parts. Use small amounts of parts; the parts are protected that way. Cob is quiet, clean--hardly any noise.
In the 2 real "Commercial" tumblers we use stone--actual graded rocks that we buy in one, and in
the other, a plastic media. Both are used with water and the plastic gets a tiny amount of tumbling
soap to clean the parts. Water quiets the process down too.
20-30 rpm is a good speed for a tumbler.
From: Nick Vincent <nathforg@cct.infi.net>
I was asked to comment on the tumbler subject since I have used some sort of tumbling device for
about 6 years now. I started out with a cement mixer(electric) that I bought at Tractor Supply for
$220. This was after I impaled myself in the abdomen with a spike at the wire wheel and fileted my
big toe and punched a hole in a new pair of boots with another spike at the wire wheel. I do
production blacksmithing, mainly small items, hooks, etc. I had been warned before I bought the
mixer, not to use an abrasive media, so I experimented with kitty litter, pellet type feed, river gravel,
etc. I found that forged steel was tougher than I imagined and bought ceramic tumbling media from
Manhattan Supply (triangular shape). This made all the difference except that it was very dusty and
noisy. I cut down the noise by wrapping foam rubber around the outside of the cement mixer. The
dust was a mess but we were hand oiling every piece at the time and the dust mixed with the oil to
give a dark finish. At least no more wounds and we were more efficient. Then the orders increased
meaning production needed to increase. I felt the finishing process was still a bottleneck. After a
conversation with Jim Bomba at a WMBG conference I decided I needed to check out the
commercial "tumblers". But his one comment I'll never forget, "Tumbling without a liquid wash is
like brushing your teeth with out toothpaste."
I checked out several tumblers, had some samples run at different places. This is something any of
the major companies will do for you, send them some samples of your unfinished product and a
finished product and they will figure out what process will work with their machine to produce your
results. I finally decided on a BurrKing Deburring machine. A tub on a stand, about 30" long 12"
wide and 15" deep, using the same ceramic media I had been using and having a bucket with a rinse
solution and a pump. A simple operation, the forged items are put in the tub, tumbled for about an
hour, rinsed then put in the cement mixer (cleaned out) with some towels to dry (about 10 minutes).
Instead of hand oiling and wiping, we then take the dried hooks, dump them in a bucket pour the oil
over them and put them back in the cement mixer with some towels for 10 minutes and they are
done. You can get whatever degree of cleaning you want by varying time and the abrasiveness of the
media. For what it does it is cheap at approx. $3000. I couldn't survive without it. I now put every
thing in there. even items that are over 30" long I will take a courtesy bend to make them fit and then
straighten them out later. Wire wheels are dangerous and time consuming, while the mechanical
cleaning is going on, I can keep forging.
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Barb noted that:
We recently converted many of our tumblers to belt driven. The noise from gear driven tumblers is deafening, and over the long run irritating and harmful. We use pulleys and belts to get the speed down.
Our large tumbler, which has doors on the side of the barrel and has 2 compartments is lined with
a non-rubber substitute. Neoprene is the rubber sub that is more resistant to oil and water. It used to
be lined with rubber, but rubber decays with the materials we tumble in over time -- LONG time,
10-15 years. Our hexagonal one is also lined. You can buy 3/8" thick rubber and line it yourself
if you are careful. We have done it and patch ours too. Lining has great noise reduction properties,
but even more important it doesn't bash the parts as badly. (Ed.: Barb does a lot of brass parts)
One of the cement mixer tumblers uses a bit of cob but most are full of parts (sand castings). We
tumble castings in the foundry to get the sand off before removing parting lines. That process is
INCREDIBLY noisy. Even the neighbors object. That is because the tumbler is unlined and we are
doing lots of parts. If you used metal scraps as your media, I cannot think that level of noise is good
for you, and after years of noise exposure, let me tell you it takes its toll. Ear ringing is no fun.
Hearing loss stinks.
Jerry Frost suggested that:
For a liner, you might talk to the folks that spray line pickup truck beds and such, like "Rhino Hide."
That may be a local name but I think it's a nationally franchised product. It's kind of expensive but
figuring in the price of rubber and your time and labor installing it, it may be cost effective. Also it
is a sprayed on product so you can weld in any style lifting flanges you like. On the other hand
modifying the tumbler would be a pain after it's lined.
We have a machine in the soils lab that is basically a really heavy duty tumbler, 30" in dia. by 24"
long by 5/8" wall, with one 4" lifting flange running the full length, mounted on the inside of the
door. The thing is charged with 6,000 grams of aggregate and 12, 1" steel ball bearings. It is
horrendously loud, physically painful with ear plugs and muff type hearing protectors both and way
above safe noise limits through four insulated walls. I was asked to see if I could quiet it down to the
point they wouldn't have to house it in a building of it's own.
I wrapped it with 1/2" felt, just glued to the outside. I was stunned, it just thumps now, you can work
in the same room without hearing protection at all. It's only making about 60 db instead of over 300
db.
From: Sherry Robinson - SBU IS - 297-7237 <robinson@sbuoa.ENET.dec.com>
We have a hexagonal tumbler with different shapes of steel shot. The lining is heavy rubber, and we have checked it for leaks/cracks and it's fine. The problem we are running into is within an hour or so of changing the liquid, the whole thing is a mess of rust - the water is rusty, even the silver pieces being tumbled turn yellowish and this does not rinse off. We have tried 2 liquid
media: one is water with Rio lapidary tumbler power [looks like soap flakes] and the other is also
Rio, a dark orange/red liquid that I can't recall the name of. The results are the same with both
and the water/liquid does cover all of the shot at all times. The shot itself is not rusty. Any idea
why this is happening? Is there something else we should be using for liquid?
nick <nathforg@cct.infi.net> offers a solution
I use Compound C from MSC about $28.00 per gallon but it does get diluted.
Their statement: "A liquid flo-thru compound concentrate, uniquely formulated for all metals
and plastics. Vibratory operations require clean processing procedures. Compound C is
specifically formulated to enhance the process. As a non-foaming compound, dirt is retained.
Soils that can load the media and darken parts are quickly flushed from the processing channel,
resulting in faster cycle times and cleaner parts. Mix 2% dilution for flo-thru, 4% or more for
post process rust inhibitor rinse."
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The Media you need depends on the job. Steel shot can be used for burnishing, larger shot or slugs for deburring. Your local machine shop may have a bucket of knockout slugs sitting under their punch press. These work fine for rough deburring and don't cost much. Some commercial shot is specially shaped so that it will reach into corners, and polished so it burnishes your parts smooth.
The corn cob, sawdust, and shell media mentioned above are used not only as absorbents to remove oil and water, but also as miniature polishing buffs when fine abrasive powders are added to the mix.
Ceramic or graded stone media provide an effective way of removing rust and scale while leaving
a uniform surface on your parts.
The following suppliers are listed for your convenience, this is not an endorsement of them or
their services. Check your local Yellow Pages under: Abrasives, Deburring, or Metal Finishers
equip. and supplies.
Indian Jewelers Supply Co. PO Box 1774 Gallup NM 87305-1774 1-505-722-4451
Rio Grande USA 800-545-6566 Canada 800-253-9738 Mexico 95-800-253-9738
Roto Finish, 1600 Douglas, Kalamazoo, MI 49007 800-992-1417
Almco, inc. 902T East Main Street, Albert Lea MN 56007 800-521-2740
Eaglemaster inc. 7410 Bush Lake Road, Minneapolis MN 55439 800-959-0543
Sterling Supply co. 459 NE Harding St. Minneapolis MN 612-331-5125
Abrasive Systems inc 8770 Valley Forge LN N Maple Grove MN 612 -424-7400
Deburring inc. 445 W Co. Rd E, Shoreview MN 612-483-4554
Manhattan Supply Company (MSC) 1-800-645-7270 http://www.mscdirect.com
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