Tumbling Questions

[Paul Alciatore]

I got one of those small tumbling machines from HF and it seems to work fairly well. I also bought a box of crushed walnut shell media for it. So far I have used it to clean up some old nuts and screws I have.

I also tried to finish some small aluminum parts with fairly good results. After with my success with the nuts and screws, I was initially disappointed with the aluminum parts. After several days of tumbling in the walnut shells they were only mildly improved so I added a bunch of nuts to the drum and they seemed to turn the trick. Apparently you need something in addition to the walnut shells to actually finish the aluminum parts. I thought of some abrasive like sand but did not want to use anything too coarse as it may have too drastic of an effect.

On another shopping trip I noticed that they do sell abrasive in small packets apparently to be added to the walnut shells. This sounds logical and there were four grades of abrasive in the box: I got one. But no instructions. So what I am wondering is exactly how much abrasive should I add to the shells for different kinds of parts? Steel, aluminum, brass, plastic? Can anybody provide guidance here or do I just have to experiment?

[Frank46]

I use walnut shells in my cartridge case cleaner. It's a vibratory type. After the walnut shells I dump it out to be reused and fill with corn chips. Definitely not the ones you eat. Brings brass to a high luster shine. Check any good welding shop and get their reccomendations. I would think an abrasive is the last thing you'd want to put in your tumbler. You are wanting to polish and deburr those parts. Sometimes on really crudded up brass I use some Bon Ami which is nothing more than ordinary scouring powder like you would use on sinks. Oh yeah the corn chips are nothing more than ground up corn cob. Hope this helps. Frank

[J Tiers]

I had some toolbox (case) hardware to clean up, had some rust/corrosion, hazy finish, etc. Have an old legitimate tumbler, about 8" diameter, not the tiny HF unit. The hardware was corners, edge straps, hinges, and handle plates. Very irregular shapes, with inside corners, etc.

Walnut shells did exactly nothing useful. Slight polishing of the rust.

Walnut shells with some abrasive did slightly more of nothing.

Some mixed old hardware did more work, but not what I wanted.

I finally went out to the shed and got some sand. That, with water, did exactly what I wanted.

A final run with walnut shells and a little oil polished up and coated them. The process cleaned up the surfaces, and gave a polish that should be a good base for replating.

[Grind Hard]

You actually need an abrasive media to remove rust and scale. Shell and Cob are great for final cleanup.

Sand works great with water, as was mentioned. I ran out of abrasive-stone media so I used a handful of gravel off the driveway, once. Worked quite well.

With aluminum and thin steel parts you will want to watch your loading, as tumbling can damage edges. For those, use a medium-fine abrasive and watch your cycle time.

[Paul Alciatore]

Hummm. I feel a wider internet search coming on.

[moe1942]

Steel shot..number 8...

[Ken Gastineau]

Paul:

Grind Bastard is steering you in the right direction. I have been tumbling jewelry for over 28 years and burnishing and polishing media (walnut shell, steel shot, ceramic burnishing media, and wood pegs) isn't going to do anything but shine up everything I want removed.

If you need to remove burs, smooth edges and/or achieve a good surface finish you need to at least prepolish and maybe a heavy cut down cycle before that.

Cutting down metal and prepolish usually involves a media that has an abrasive grit in it. The media is engineered to wear down and expose fresh grit as it breaks down. This requires a solution to be pumped and circulated through the tumbling media/work pieces so as to flush the media/metal bits that accumulate away or at least dilute it so it does not turn into thick soup and slow or stop the abrasive action of the media on the work pieces. If you tumble pieces without achieving enough abrasive action on the surface of the metal, you end up beating it with the media and this results in an orange peel looking surface when polished.

Once a proper cut down/prepolish has been achieved, then the work is tumbled in a wet or dry polishing media like steel shot, ceramic burnishing media, treated wood pegs or treated walnut shell to bring about a polished surface.

Vibratory finishing is both an art and a science. Industrial equipment is far superior to any of the hobby or "professional" grade stuff that I have used. Size, shape and grade of media can be critical to many applications as well as machine speed and counterweight settings.

In any event, mass finishing sure beats the heck out of polishing on a buff wheel when there are lots of small parts involved.

Ken Gastineau
Gastineau Studio

[amatts]

I got one of those small tumbling machines from HF and it seems to work fairly well. I also bought a box of crushed walnut shell media for it. So far I have used it to clean up some old nuts and screws I have.

I also tried to finish some small aluminum parts with fairly good results. After with my success with the nuts and screws, I was initially disappointed with the aluminum parts. After several days of tumbling in the walnut shells they were only mildly improved so I added a bunch of nuts to the drum and they seemed to turn the trick. Apparently you need something in addition to the walnut shells to actually finish the aluminum parts. I thought of some abrasive like sand but did not want to use anything too coarse as it may have too drastic of an effect.

On another shopping trip I noticed that they do sell abrasive in small packets apparently to be added to the walnut shells. This sounds logical and there were four grades of abrasive in the box: I got one. But no instructions. So what I am wondering is exactly how much abrasive should I add to the shells for different kinds of parts? Steel, aluminum, brass, plastic? Can anybody provide guidance here or do I just have to experiment?

Several years ago,I invested in a 5# raytheon(US Made) vibratory finish mill. Try a local jewelers supply for media choices.I use plastic,steel shot,and ceramic media(HF) with good results on ferrous and non ferrous material.The HF triangular media works the best on rust removal,w/o alter the shapes or threads.

[Grind Hard]

Emphaisis on the ART here, Ken. Company I'm at used to relegate this to a menial task and assign the low-level labor to it.

Now I oversee tumbling and I've got a good grasp on what works for what situation.

Dry tumbling is ok, but ultimately you'll need to keep your cycle short as you end up pounding the abrasive dust into the part.

On the small vibros, throw in a couple of cups of your favorite coolant mixture with your media. That'll help keep the dust down and allow things to circulate somewhat.

If you really want to get technical, set up a flow system. Pump water in one end and suck the waste slurry our the other. THIS will give best results but is difficult to set up in the home-shop.


So in conclusion, do what Ken suggests, and what I suggested too. Abrasive for the first pass, followed by a burnish/polish pass with shells or cobs.

Good luck!

Paul:

Grind Bastard is steering you in the right direction. I have been tumbling jewelry for over 28 years and burnishing and polishing media (walnut shell, steel shot, ceramic burnishing media, and wood pegs) isn't going to do anything but shine up everything I want removed.

If you need to remove burs, smooth edges and/or achieve a good surface finish you need to at least prepolish and maybe a heavy cut down cycle before that.

Cutting down metal and prepolish usually involves a media that has an abrasive grit in it. The media is engineered to wear down and expose fresh grit as it breaks down. This requires a solution to be pumped and circulated through the tumbling media/work pieces so as to flush the media/metal bits that accumulate away or at least dilute it so it does not turn into thick soup and slow or stop the abrasive action of the media on the work pieces. If you tumble pieces without achieving enough abrasive action on the surface of the metal, you end up beating it with the media and this results in an orange peel looking surface when polished.

Once a proper cut down/prepolish has been achieved, then the work is tumbled in a wet or dry polishing media like steel shot, ceramic burnishing media, treated wood pegs or treated walnut shell to bring about a polished surface.

Vibratory finishing is both an art and a science. Industrial equipment is far superior to any of the hobby or "professional" grade stuff that I have used. Size, shape and grade of media can be critical to many applications as well as machine speed and counterweight settings.

In any event, mass finishing sure beats the heck out of polishing on a buff wheel when there are lots of small parts involved.

Ken Gastineau
Gastineau Studio

[aboard_epsilon]

search rock tumbler media on ebay ..

perhaps that will work better

i have a tumbler ..but i dont have the barrel .

all the best.markj