I'm thinking of getting this big rock tumbler to use in surface finishing aluminum front panels, heatsinks, etc. Prior to anodizing them all at home. I've tried sanding, buffing, lapping on glass, random orbital vs rotary sanding, etc. all sorts of ways, I get good results but not "repeatable" results from piece to piece, especially if I'm progressing through six to eight different grits of sandpaper. I thought well maybe I should get a glass bead blasting cabinet, but thats still a manual operation, and I dont have much room left in the garage. And also its a skill I'd need to learn and you need a very high CFM air compressor for one of those. I certainly dont have room for a large floor standing air compressor. I also looked at vibratory tumblers, but they are expensive and usually use a bowl with a rod down the middle which would mean I cant do long plate stock. The largest ones run close to $2,000
Then I thought I had a brilliant idea (those usually fail me)... Maybe I can find a large sized rock tumbler to do a "set it and forget it" tumble of my aluminum parts so that all the parts of an amp have precisely the same surface finish. The largest size panels I plan on doing would be 12 inches by maybe 9 inches, because that fits nicely in my mini CNC machine. Heatsinks, there are a few I like from heatsinkusa, the 6 inch wide and 4.5 inch wide ones usually cut to 3 inch length. So those are my largest part sizes.
Well, I found this large rock tumbler model which is widely used in the commercial rock tumbling world, it has a 15 inch by 15 inch drum to hold any sort of tumbling media I could think of and also hold the largest parts I'll be making... (link below). It sells for about $850 bucks everywhere and I can drive to pick it up. I'm figuring I could machine all my parts and heatsinks, then simply tumble them for a set number of days, hoping they will emerge from the magical drum with consistently the same and beautiful surface finishes. It's even water tight so I can tumble with wet media, try out different media, walnut shells, ceramic media, 2mm stainless beat shot, plastic abrasive media, corn kernals, etc. Then I'll anodize them (which I am already set up for in the garage).
What do you guys think? Will this work?
https://kingsleynorth.com/65t-heavy-duty-commercial-tumbler.html
Then I thought I had a brilliant idea (those usually fail me)... Maybe I can find a large sized rock tumbler to do a "set it and forget it" tumble of my aluminum parts so that all the parts of an amp have precisely the same surface finish. The largest size panels I plan on doing would be 12 inches by maybe 9 inches, because that fits nicely in my mini CNC machine. Heatsinks, there are a few I like from heatsinkusa, the 6 inch wide and 4.5 inch wide ones usually cut to 3 inch length. So those are my largest part sizes.
Well, I found this large rock tumbler model which is widely used in the commercial rock tumbling world, it has a 15 inch by 15 inch drum to hold any sort of tumbling media I could think of and also hold the largest parts I'll be making... (link below). It sells for about $850 bucks everywhere and I can drive to pick it up. I'm figuring I could machine all my parts and heatsinks, then simply tumble them for a set number of days, hoping they will emerge from the magical drum with consistently the same and beautiful surface finishes. It's even water tight so I can tumble with wet media, try out different media, walnut shells, ceramic media, 2mm stainless beat shot, plastic abrasive media, corn kernals, etc. Then I'll anodize them (which I am already set up for in the garage).
What do you guys think? Will this work?
https://kingsleynorth.com/65t-heavy-duty-commercial-tumbler.html
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FWIW, way back when I was into all manner of slotcar, RC, etc., scratch building chassis out of brass rod, sheet, piano wire, etc., it's what I used plus cleaning rusty tools and with different grit even cleaned fine jewelry, some plastic parts, so IME money well spent, using it the other week to clean a neighbor's airless spray gun after spraying a (too) quick set epoxy.
No,you would need HUGE rock tumbler, say 10X the size of your panellength ... obviously impractical.
Becuse "surface grinding" action is not uniform at different points inside.
It works for small parts (I use one to clean cartridge brass before reloading) because they are rolling and tumbling in all directions possible but a panel,even IF it fits, is too large for that.
I suggest blasting.
Sand is too rough and aggressive but you can get glass micro beads, which are rounded shape, result will be a beautful and very even satin finish.
By the way, that´s what Factories and Pros use.
Becuse "surface grinding" action is not uniform at different points inside.
It works for small parts (I use one to clean cartridge brass before reloading) because they are rolling and tumbling in all directions possible but a panel,even IF it fits, is too large for that.
I suggest blasting.
Sand is too rough and aggressive but you can get glass micro beads, which are rounded shape, result will be a beautful and very even satin finish.
By the way, that´s what Factories and Pros use.
Heatsinks are especially impossible to finish the area between the fins, so I would think this is ideal for that. I'm looking to get a matte finish that I can repeat, that's the key repeatability over time and projects.
JMFahey
"No,you would need HUGE rock tumbler, say 10X the size of your panellength ... obviously impractical."
Lets say if I placed a 12 inch long by 3 inch high by .25 inch plate into this 15 inch diameter octagonal drum, I understand that it will stay longitudinal in the drum, but it will be flipping over because the drum itself is octagonal, making everything more aggressive. I would think that should be ok. The abrasive might always flow in one direction across the face but I would think still give a matte finish after a time. I really think experimentation is the only way to determine what happens. I understand a glass bead blaster cabinet but it's that $1,000, big, high CFM air compressor my garage is packed. So I need to improvise, I have a spot for this tumbler. If it fails I guess I could just make shiny rocks!
JMFahey
"No,you would need HUGE rock tumbler, say 10X the size of your panellength ... obviously impractical."
Lets say if I placed a 12 inch long by 3 inch high by .25 inch plate into this 15 inch diameter octagonal drum, I understand that it will stay longitudinal in the drum, but it will be flipping over because the drum itself is octagonal, making everything more aggressive. I would think that should be ok. The abrasive might always flow in one direction across the face but I would think still give a matte finish after a time. I really think experimentation is the only way to determine what happens. I understand a glass bead blaster cabinet but it's that $1,000, big, high CFM air compressor my garage is packed. So I need to improvise, I have a spot for this tumbler. If it fails I guess I could just make shiny rocks!
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I've never tried tumbling aluminum but I think a blasting cabinet is a better route to take, thats what I use (though I mostly do side panels). And I like to use a light patina where slight variegation in the blasted finish looks fine. Maybe it would be fussy if you plan to anodize... I don't know. I also think the tumbler will have a hard time reaching into crevices in things like heat sinks.
If you are willing to work somewhat patiently, you can get though blasting small/medium parts without a huge compressor. Also, my compressor has always lived outside under a tiny awning and holds up fine (though I live in the South West, so the weather is mild).
Hopefully you will get a reply from someone with experience using a tumbler, but if it were me, I would invest in a decent compressor (they have a hundred uses) and get a super basic bench-top blasting cabinet.
If you are willing to work somewhat patiently, you can get though blasting small/medium parts without a huge compressor. Also, my compressor has always lived outside under a tiny awning and holds up fine (though I live in the South West, so the weather is mild).
Hopefully you will get a reply from someone with experience using a tumbler, but if it were me, I would invest in a decent compressor (they have a hundred uses) and get a super basic bench-top blasting cabinet.
Attachments
Heatsinks are usually anodized for a reason - so they can radiate heat, the bare metal has very low emissivity, anodized surface has very high emissivity. If you have bare Al heatsink the best thing you can do is anodize or paint it so the the surface can radiate heat.
Understood about radiating, it also makes them non-conductive thus safer but should be safety grounded anyway I guess. I've anodized heatsinks but without doing any surface work, just cleaning of course and a pre-etch with caustic soda. I mask the whole backside to have ultra smoothness for the grease. This does give a matte finish so I suppose I could forego blast beading or tumbling of heatsinks. So I guess we're only talking about surface finishing plate stock. The more I think of it I should get a small blast cabinet and a larger compressor than my brad nailer compressor. JMFahey is probably right about plate stock not really tumbling all that well. Oh well.
Been researching how to set up a small glass bead blaster on the cheap. For Amp parts it turns out I don't need a whole lot of continuous air so a smaller 1.5 HP compressor is fine. Harbor Freight has a small blast cabinet for $250; and the gun and media hopper for under $40; and a 20 gallon compressor for $239 that will fit in a corner; and the media too all from one store down the road. I was thinking it would be costlier to get into bead blasting, but this is less the price of my crazy idea for a rock tumbler. I was also mistaken about the air quantity needed, continuous blasting would require a huge compressor, but for small amp parts you're stopping the gun often touching up so the air recovers. My small pancack compressor won't cut it but this 20 gallon one should be plenty. Under $700 and I'm set up.
gun
https://www.harborfreight.com/portable-abrasive-blaster-kit-37025.html
cabinet
https://www.harborfreight.com/benchtop-abrasive-blast-cabinet-62454.html
compressor
https://www.harborfreight.com/20-gallon-16-hp-135-psi-oil-lube-vertical-air-compressor-64857.html
bead media
https://www.harborfreight.com/50-lb-glass-bead-80-grit-abrasive-media-56706.html
gun
https://www.harborfreight.com/portable-abrasive-blaster-kit-37025.html
cabinet
https://www.harborfreight.com/benchtop-abrasive-blast-cabinet-62454.html
compressor
https://www.harborfreight.com/20-gallon-16-hp-135-psi-oil-lube-vertical-air-compressor-64857.html
bead media
https://www.harborfreight.com/50-lb-glass-bead-80-grit-abrasive-media-56706.html
You might consider building a tumbler that would involve a motor, pulleys, 2 shafts, one of which is driven by the motor/pulley system, and simple frame to cradle a drum of sufficient size. Drums can be gotten from Uline. https://www.uline.com/Product/Detail/S-19419/Drums/Plastic-Drum-with-Lid-30-Gallon-Open-Top-Natural
Would probably be cheaper than the commercial units... This is DIY, after all.
Would probably be cheaper than the commercial units... This is DIY, after all.
I hate to beat this to death but others might be interested in getting into blasting media. I've discovered that I don't have to buy a new compressor or a separate gun. Harbor Freight sells a blaster with just an air tank and a media hopper and gun for $160. So all I need is this and the cabinet. I'd use my little pancake compressor to simply fill this tank with air then blast away, saves me space and money, and it would be quieter too. $250 cabinet + $160 blaster + $20 for some media!
https://www.harborfreight.com/search?q=110 lb. Pressurized Abrasive Blaster
https://www.harborfreight.com/search?q=110 lb. Pressurized Abrasive Blaster
Yes, I think blasting is the better way to go here.
While traditional rock tumblers normally have large drums, there are other more efficient (and faster) smaller tumblers for finishing smaller parts, called vibratory tumblers. I used one for smoothing and polishing parts cast from resin using abrasive ceramic beads. It should work very well for aluminium parts, but not large heatsinks.
Example of such a tumbler:
https://www.amazon.com/Frankford-Ar...words=vibratory+tumbler&qid=1696259220&sr=8-3
While traditional rock tumblers normally have large drums, there are other more efficient (and faster) smaller tumblers for finishing smaller parts, called vibratory tumblers. I used one for smoothing and polishing parts cast from resin using abrasive ceramic beads. It should work very well for aluminium parts, but not large heatsinks.
Example of such a tumbler:
https://www.amazon.com/Frankford-Ar...words=vibratory+tumbler&qid=1696259220&sr=8-3
I have a small blast cabinet I picked up for a bike rebuild (20 inch girls bike / small cruiser). I have worked a LOT of aluminum and the right medium makes all the differance. Glass beads for a nice matt to satin finish or walnut shell for a satin to "soft-gloss" finish.
Just don't use Alum Oxide trust me (and please don't ask how I know!)
Used 44 gallon drum, with removable lid.
Fill half up, close the lid firmly, and roll down an incline, say 200 feet.
Repeat if needed.
Can add cement mixer fins.
I saw this being used to mix paint, there was no tax for paint made without electric power.
The guy had a hoist, a trolley and a long incline made with angles in his factory, used to make 100 liter batches of oil based paint...add all ingredients, mix them by rolling down an incline.
I see no reason why this method cannot be used for finishing aluminum, add job and media, roll down a slope.
Have fun.
Or find a commercial sand blasting service, it is a common procedure in construction and ship repair.
Fill half up, close the lid firmly, and roll down an incline, say 200 feet.
Repeat if needed.
Can add cement mixer fins.
I saw this being used to mix paint, there was no tax for paint made without electric power.
The guy had a hoist, a trolley and a long incline made with angles in his factory, used to make 100 liter batches of oil based paint...add all ingredients, mix them by rolling down an incline.
I see no reason why this method cannot be used for finishing aluminum, add job and media, roll down a slope.
Have fun.
Or find a commercial sand blasting service, it is a common procedure in construction and ship repair.
Mark, can you recommend a type and/or brand of paint that works well for heatsinks? I have some that are clear anodized and I would like to paint them black for cosmetic reasons but I've been concerned paint may have thermal insultaing properties. So far I haven't found any paint that is specified as thermally conductive. Thanks in advance.
