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Barrel tumbling - hsm style

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  • Barrel tumbling - hsm style

    I have a numer of small parts to deburr / finish that are 1018CRS, ~1/2"dia by 3/8" length. 7/32 thru bore. I wanted to try some finishing rather than just leaving them as-turned this time. Here's my plan; I welcome your comments.

    Load a quart painters can with 1:4 :: parts:media. Tape lid closed and put can in large plastic bag. Mount on my bench speed lathe (no compound) that has a 6"-dia. chuck. Put on highest speed (~700rpm iirc). Use sand as media mixed with a little soapy water and water-soluble rust inhibitor. Empty. Clean. Repeat dry this time using a walnut-shell like substitute, i.e. whatever I can find cheap at the pet store.

    Main areas for questions from my perspective:
    *any guesses at run time?
    *other than the last step, this is all using material I already have on hand. is there a better media recommendation, though, than regular sand that can be had for basically no cost?
    *part:media ratio sound reasonable?
    Last edited by Arthur.Marks; 12-31-2011, 04:13 PM.

  • #2
    someone else may have different/better idea however I think RPM seems high,maybe 60 RPM
    geno

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    • #3
      While it has been a long enough time since I did any tumble finishing of parts that I can't comment to specifically about your questions, I might suggest that you would want to spin much slower than 700 rpm. At that speed the stuff will tend to get thrown out against the sides of the can so there will be minimal "tumbling" going on.

      Otherwise, sounds plenty reasonable at a glance.

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      • #4
        The tumblers I'm familiar with don't run fast, closer to 50 rpm. If you go too fast the material won't slide/tumble rather ride around due to centrifugal force pinning everything to the barrel wall.
        Loose silicon carbide is not expensive and would work better than sand but sand should get you there.
        Run a few scrap pieces for an hour or two. The finish you get should give you an idea of how long they need to run to get the finish you desire.
        Fill the container about 3/4 to leave room for the tumbling action.

        Have a good one, Jim

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        • #5
          Agree, your'e RPM is way too fast.

          Centrifical force at that speed will have everything clinging to the outside, which will produce a major "Balance" problem.

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          • #6
            The polishing action of a tumbler is achieved by revolving the drum at a speed JUST SUFFICIENT to drag the mix of media and parts up the side of the drum to where it "curls" like a wave and the parts return to the bottom. If the speed is any higher, the parts ride high enough to drop nearly vertically and there is very little polishing action.
            To perhaps make it clearer, if the "parts" are of some brittle material like glass or agate, then when they drop, they chip and continually reduce in size. At the slightly lower speed, they only wear by rubbing against the media, so that the degree of "polish" is determined by the grit size and the time in the drum.
            For tumble polishing rocks, a rule-of-thumb is one week on each of coarse, medium, fine, pre-polish and polish. the first three are silicon carbide grit, the pre-polish is tin oxide and the polish is soap-and-sawdust.
            Note, you have just spent FIVE WEEKS! That is just ONE example of a technique; there are many variations, but they all take time.
            Duffy, Gatineau, Quebec

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            • #7
              Hmmm... So is 200rpm too fast even? That is the slowest speed on the lathe I was going to do it on. I was thinking a day or two maybe---not five weeks

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              • #8
                I use a rock tumbler, they work great for nuts and bolts and small parts!



                Derusted, cleaned, painted like new again.

                Andy

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                • #9
                  I found a rock tumbler for cheap ($30.00) at harbor fright last year. Works very well for what you are talking about.

                  Tim

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                  • #10
                    Originally posted by Arthur.Marks
                    Hmmm... So is 200rpm too fast even? That is the slowest speed on the lathe I was going to do it on. I was thinking a day or two maybe---not five weeks
                    Well, 5 weeks is for rocks that start out well, Unmachined Very.. rough! natural products yaknow... lots of large points that need wearing down with 60grit then 120 then 200 then 400 then 1000 then 2000 then polish. All aobut a week each. The diffrent grits are kinda fun to play with it and have around. 2000 is like abrasive flour. 60 is like very course sand.

                    The pointy rocks come out as smooth as babys bottoms after 5 weeks though!

                    Abrasives are so cheap I would'nt bother using subsitutes, You'll need the proper mesh size for the job/finish or you'll just end up puting dents/scratchs into things with random sand.

                    Yea, 200rpm is likey too fast still. its seriously a drop dead boring operation, I ran my rock polisher in the basement where I could'nt hear it, I think it ran at even less then 60rpm, maybe 20~ rpm, with just a 3" drum (larger drum = less rpm), so 60rpm is likey the ABSOLUTE fastest you'd want to go with any decent sized drum.

                    Also note that most rock polishers operate with water in the mix, if the part can rust, im sure oil will work just as well, just messyer.

                    If you do use sand, Do not do it dry, the dust fumes will be *VERY* hazordist to your health.
                    Last edited by Black_Moons; 12-31-2011, 08:22 PM.
                    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                    • #11
                      At a rough guess my RCBS carrtrige tumbler rotates aroud 30-50 rpms. So yes, physics dictate a low rpm. It's not just the tumbling that makes it work, Your parts and tumbling media will also slide across each other and that's what does the majority of the work.

                      Pete

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                      • #12
                        Arthur, 200 rpm is still too fast. I think the other guys who suggest 30-50 know what they're talking about.

                        I have an old technical book you might find at your library, perhaps via interlibrary loan. "Handbook Of Barrel Finishing" by Enyedy, published by Reinhold. Actually, it's only a few bucks on amazon:
                        http://www.amazon.com/Handbook-Barre.../dp/B002BO34RO

                        It's a reasonably good book on the subject. Written in the mid-'50s, still covers the basics.

                        metalmagpie

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                        • #13
                          I used a cement mixer with the paddles taken out. I had quite a bit of metal parts to do and it worked pretty good. I let it run for four hours.

                          I just used some sand, pea stone and soap and water.
                          Location: The Black Forest in Germany

                          How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                          • #14
                            As far as timing, I once picked up a trucker's chain off the highway in winter. It was rusty. I took it to my buddy's house who had a big tumbling barrel. I threw it in there with a few handfuls of sand, turned it on, and left it for about a day. The next day it was clean. I oiled it and still have it somewhere, probably 30 years later. Now chain tumbling on itself is going to be pretty aggressive, so I might have only needed like 4 hours. But that's kind of your span, Arthur, something like 4-24 hours. I was going to derust and my goal was a clean surface, though. If your goal is to debur edges it may be way different.

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                            • #15
                              well figured i would show my home built tumbler. Crude but effective.

                              A ebay motor with gear reduction bolted to a half of a 5 gal. plastic can. made a round end plate with a small door and presto..a tumbler.




                              and a bonus. A video of it rotating so you can see rpm.lol

                              It does a good job. I dug it out after reading this and since I have it out I threw some 5c collets that i bought that were a little rusty. we will see how new they get. : )
                              Last edited by j king; 01-01-2012, 05:32 PM.

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