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scmw
07-10-2011, 08:38 PM
I'm profiling a bunch of .850" x .850" x .060" parts in 6160 aluminum. Other parts are .500" x .800" cylinders and so on. Most are under 1" x 1" x 2". They're for some models that I'm working on. The profiled parts have a minimal burr on the edges. Would the use of a shell tumbler (as used by gun owners who pack their own ammo) help in cleaning the edges or am I doomed to sitting at the bench filing and sanding them down manually? :rolleyes:

Does anyone have any experience tumbling 6160 aluminum in one of these small tumblers? Would the parts retain their shape or would the edges take on a rounded over appearance? Maybe that would be due to the length of time they're left in the hopper.

Thanks in advance,

Toolguy
07-10-2011, 09:09 PM
I have done a lot of aluminum parts that way. Mostly in a 3 cu. ft. industrial tumbler. That takes 2 to 3 hours due to a lot of weight of media. Sometimes that one is not available so i have to use one of my brass tumblers. It works, but takes a day or 2 due to the small weight of media. I use the ceramic stone media for the big tumbler and some water with a little dishwashing soap (Dawn) to keep the media from getting clogged with aluminum. Once finished, I rinse off good with clean water and dry well. Most of my parts are going to be anodized and any water spots make spots in the anodized finish. The end result is parts with evenly small radiused corners, much better than by hand and no parts get overlooked. Remove any big burrs first, the tumbler won't get them. It will do small burrs and sharp corners. The rest of the part will not be changed.

Paul Alciatore
07-10-2011, 10:20 PM
Question here on tumbling. From the answers I take it that the bigger the volume of media, the faster the action. Is this so? Any limits on this rule?
And you use water and detergent in the drum? I guess I was under the impression that it was done dry.

Toolguy
07-10-2011, 10:43 PM
The larger the volume of media, the more weight is on the parts when they circulate to the lower areas of the container. The more weight is on the parts, the more scrubbing action there is. If the ceramic media is run dry it gets coated with metal particles and is eventually no longer abrasive.

Steve Seebold
07-10-2011, 10:45 PM
I tumble aluminum parts all the time. I have 2 vibratory tumblers. One is a 10 quart Burr King and the other is a 3 quart Burr King. I use the larger one to debur larger parts, and I use a gray colored cylinder that's about 1/2 inch diameter, 3/4 inch long with angles on both ends. It does a great job, but you really need to keep the media clean or it will really mess up the finish on your parts.

The small tumbler uses a ceramic media that will more polish than debur. It works best on really light burrs and I use it a lot on brass parts. They come out almost polished.

JoeFin
07-10-2011, 11:33 PM
To address the Op's question

Walnut Shells produce a finish some where between Matte and Polish and should not round your corners. Probably too light for most applications needing to remove light milling or lathe imperfections.

I have a couple vibratory finishers and run 6160 frequently. 1 uses a 3/8 x 1/8 triangle ceramic and the other has mixture of 3/4 cones, 3/4 pyramids and 1/2 angle logs. I have noticed the 3/8 x 1/8 triangles cut aluminum pretty quickly and leave a light matte finish. I follow that with Dry Green to give them a High Luster Polish

scmw
07-11-2011, 12:24 AM
Wow, there's more to it than I had originally thought.

Joe, what is "Dry Green" I'm thinking green sand that's used in foundry casting but that doesn't sound right. Doesn't green sand contain some sort of binder? If that's the case, I would think that it would clog up the media. Clear as mud right? :rolleyes:

Thanks,

SGW
07-11-2011, 07:39 AM
I took a tour of the Starrett factory some years ago. The tour included a visit to the tumbling room. It was LOUD! They had a number of tumblers and a great variety of tumbling media. I got the idea that choosing the proper tumbler and proper media to use for a given part is somewhat of a Black Art, learned through experience, though I'm sure there are general principles.

JoeFin
07-11-2011, 11:22 AM
Wow, there's more to it than I had originally thought.

Joe, what is "Dry Green"

Thanks,

Dry Green is Walnut Shells coated with a Green compound. As the name suggest you have to make sure your parts are completely dried off and then run the media dry. Best part is it doesn't make a lot of noise like the ceramics do.

Because the weight of the media is so much lighter then ceramics I use just the large vibratory from Happy Fart for this.

And yes Tumbling parts is some what of a "Black Art". If there is enough money in the project you can send a few sample parts to firms who specialize in tumbling media and they will custom mix the ceramic media to the parts and even sell you the proper machine to run it. Of course we are talking 200lbs of media minimum and tumblers that start at $3500.

Or you could be like me and buy 25lbs of mix media from a friend who was running parts, try a few various ceramic media shapes, plastic triangles, and various preps such as bead blasting until you come up with a formula that works well with Al parts

Rustybolt
07-11-2011, 12:30 PM
I took a tour of the Starrett factory some years ago. The tour included a visit to the tumbling room. It was LOUD!



Think so? When I was a kid I got a tour of the International Harvester factory in Melrose Park, Illinois. The were tumbling engine blocks for excavators. It was a Wheelabrator machine and it was two stories tall.

scmw
07-14-2011, 08:53 PM
I ordered a Lyman 2500 today from Midway. Should be here on Monday. Where can I get a decent media that will remove the burrs without damaging parts? I don't mind a matte finish, just don't want bent parts. My concern is with the .040" and .062" material.

I saw this (http://www.harborfreight.com/5-lbs-rust-cutting-resin-abrasive-media-93832.html) listed at Happy Fart. Will this work or is it money wasted?

Thanks,

bobw53
07-14-2011, 09:22 PM
Those crappy green triangles actually work pretty well. They stink though.


http://www.gravescompany.com/grit.htm#Metal%20Media
place to get the walnut shell stuff, which makes it shiny.

As an aside, you may want to invest in one of them thar deburring wheels. Maybe $60, but they are the best $60 you'll ever spend, probably last you years and years in a hobby shop.

scmw
07-19-2011, 11:24 AM
When you say deburring wheel, is this like the hard white Norton wheels or would it be more like a wire brush wheel?

The Lyman arrived yesterday. I also picked up some walnut media from them. I believe that it includes rouge or something similar as the media is red. I polished some test pieces that came out well. I tossed in some of the aluminum parts with burrs, it did minimal removal of the burrs but I like the matte finish that the flats took.

So it looks like I need to manually debur them or would a ceramic media do that without doing too much damage to the aluminum?

Thanks,

Toolguy
07-19-2011, 12:05 PM
The deburring wheel is Sctchbrite, not a stone. All the industrial supply places have them. The ceramic media will gently deburr the sharp edges and put a matte finish on the flat parts but not change the dimensions of the part.