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  1. #1
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    Default Need Your Terrific Tumbling Tutoring

    Howdy:

    I'm not a regular visitor here, but could use your insights. There's so much knowledge in these pages.

    I own a guitar pick company that makes really expensive picks. Our cheapest model is $30. We are three years in business and doing extremely well.

    Here's our store: charmedlife | store

    Our main line of products is made from a strange bioplastic called CASEIN plastic. If you're familiar with casein nutritional supplement, it's made from the same stuff -- milk, plus the addition of an acid. We don't make the stuff ourselves but buy it overseas (it never caught on in the States). This particular material gives the tone and feel of genuine tortoise shell picks, which were outlawed in the seventies. It also is considered one of the most beautiful plastics in the history of mankind, and can be colored almost any color. To this day it is known as the "Queen of Plastics." Here's a snap of our most popular model. Pretty cool, huh?



    Okay, now the problem. This stuff is far and away the most difficult material in the world from which to make guitar picks. It's just brutal. It cannot be injection-molded, so you must but sheets about 4.0 mm thick (.160") and machine it from finished stock. And that's just the beginning of the fun.

    It does not like heat, and it HATES water. 15 minutes of exposure to water warps it and makes it unusable.

    Once the material is cut into a pick shape and ground down to, let say, .040" (1.0 mm), the edges must be fully radiused and the pick buffed and polished. It shows the tiniest micro-scratches and requires a lot of man hours. I'm looking for a way to automate.

    Sorry to drag this out. Has anyone ever tried vibratory tumbling with oil instead of water? This stuff is fine which all oils I've tried on it, but will the oil just negate any cutting and deburring because it increases lubrication?

    I'll stop here. Appreciate your insights. I'll figure it out, but just trying to reduce my trial-and-error, which has already cost me thousands of dollars and thousands of hours of experimentation.

    All the Best,
    Scott

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    Can you restate that as a question please?

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    Have you tried Dry tumbling? Walnut shells or corncob?

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    Quote Originally Posted by beege View Post
    Have you tried Dry tumbling? Walnut shells or corncob?
    I remember reading years ago when " Ray-Ban " were really " Ray-Ban " and made in the USA tumbling with walnuts was how they finished their " Wayfarer " style frame.

    Regards Tyrone.

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    I see no reason why tumbling in oil wouldn't work. Might have to experiment to get the right viscosity.

    Not to side track the thread, but can you make custom picks? I have a unique requirement.

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    Quote Originally Posted by Larry Dickman View Post
    I see no reason why tumbling in oil wouldn't work. Might have to experiment to get the right viscosity.

    Not to side track the thread, but can you make custom picks? I have a unique requirement.
    Me too Larry, one that allows me to play the guitar with no musical ability whatsoever. Just a little bit, I'm too old to be the next Jimi but playing like Eric would be OK.

    Sorry to interrupt the thread.

    Regards Tyrone.

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    Quote Originally Posted by Larry Dickman View Post
    I see no reason why tumbling in oil wouldn't work. Might have to experiment to get the right viscosity.

    Not to side track the thread, but can you make custom picks? I have a unique requirement.
    Larry, thanks for you thoughts on tumbling with oil. Doesn't hurt to try. I looked up viscosities for regular kitchen oils and it looks like walnut and coconut are among the lowest. So worth the experiment.

    On the custom pick thing, not likely. Right now we're running two to three weeks backlog on people who have already paid and are waiting. This is because I'm having to hand-make and hand-finish almost every one of these puppies. But do email me directly if you like at charmedlifepicks @ gmail.

    Thanks again so much,
    scott

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    Quote Originally Posted by 3t3d View Post
    Can you restate that as a question please?
    Diamond, in short, I'm looking for a vibratory tumbling solution that does not use water.

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    Folks, to roll several responses into one post, I've tried dozens of different combinations with both corn cob and walnut. No go. I even bought diamond dust down to 220 grit and ran it embedded in walnut shell for two weeks solid. No go. Same thing with corn cob.

    The main thing, folks, is I need something much more aggressive than embedded cob or walnut shell. Those are good for finishing above, say, 14,000 grit rating, but not for this. I'm really seeking more of a strong deburring process, something pretty aggressive. I've done it running about a pound of straight 220 grit, but the heat from the friction warps the material. I've also tried half-and-half walnut shell/220 grit -- takes forever.

    I just ordered some plastic cones to try those, since they can run dry.

    BTW, Diamond Pacific has a series they call Vibra-Dri. Ran 600-1700-3000-8000. Even 600 is not aggressive enough.

    Thanks!
    Scott

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    I'd try dry first..

    Then if you want "oil", I'd try and replicate the viscosity of water as close as you could..
    Diesel fuel maybe? Its cheap compared to "OIL".. And its not water as long as you don't
    get it from Larry's gas station.

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    Any reason you haven't let one of the many finishing companies out there do some trials?

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    Have you tried a rotary or polygonal rotating type tumbler instead of a vibratory type? It should run cooler and may make dry running possible. (Viking brandis an example of the latter)

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    Original question,
    We use kerosene for 2 reasons:
    #1 on small diameter hypo tubing it cuts about 3 or 4 times faster than water based compounds
    #2 on steel parts that I do not want any rust
    That said kerosene or maybe honing oil will cut faster, but also give you a rougher finish that water based products, picture a lot of fine scratch marks. It would definitely round the corners of your "plastic" parts fast, then you would need to change to metal ball cones or something else to shine up the finish. One special Hypo tube we do, we run them in kerosene for a little while, do some finish machining back into the tumbler for a while with water based compound then over night with water based compound and porcelain burnishing stones. We get a mirror finish this way. Where ever you get your tumbling media and compound should be able to develop a process for you. Give them samples of what you are after as well as some parts ready to finish.
    If you use kerosene or a honing oil do not mix the media up with anything you will use with water based compounds. It will make a mess as the oil comes out of the media into a water based compound.
    You can reuse the oil/kerosene by setting aside and letting the fines settle out. Dirty compound will impart a dirty finish, change your compound shortly before removing your parts to get the cleanest finish.

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    If you need moderate/low material removal and good finishes, you should try a rotary tumbler instead vibe, and if the removal rate is low, you can always add "ballast" material
    such as small balls or pins.

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    Perhaps something like the polishers used for metallurgical sample polishing, these are slow-rotating horizontal discs that can have diamond-embedded plates, sandpaper, or cloth laps charged with whatever abrasive/lubricant is required. These also may have holders that rotate multiple sample pucks against the disc. A disc with the pick outline cavity could serve as a holder. If a nappy felt-like cloth is installed on the plate, it naturally rounds any sharp edges. Silicon-carbide, alumina, diamond, with oil are typical abrasives used to charge the cloth laps. (I wish I had $5 for every metallurgical or other cross-section I polished in the past....). More than one polishing step/grit would be needed.

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    I am not sure you want a tumble type device. it does not seem to suit what you want, which is a good surface finish plus rounding of the edges.

    I like the general idea that car2 suggested. if you use a vacuum fixture, you could line up several pieces, and do them all at once, depending on how big the machine is (have not used that type).

    My experience tumbling parts has been that the process does Ok on edges when the part is somewhat "chunky", has appreciable width, thickness and length. But if the part is more two-dimensional, the edges do not get done reliably. This could be due to poor setup on my part, of course, so if others think it will work, then OK.

    Most picks are pretty smooth, though, and a process that polishes the surface while cutting the edges seems ideal, so the soft polishing wheel seems like a good plan.

    If that cuts the surface too much, then you might use the vacuum fixture idea again, and actually cut out the parts with a small CNC, using a rounding cutter to do it. If you register the blank well, you should be able to cut a sheet of them at a time, not cutting through, but cutting a little less than halfway, then flipping over. You;d need a custom cutter, but they can be obtained. The final step would be to cut the outline, and then the parts could be polished without the need to get any significant cutting on the rounded edge, just polish it.

    You would have the thicker sheet ground down to near final thickness prior to doing the above work. Leave just enough that polishing brings it to the desired thickness. So you would be cutting a radius of maybe 0,4mm on the edges, accounting for the custom cutter.

    maybe that will not work with the casein plastic, I have never worked with the stuff.

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    dpolseno41:

    Yeah, one of the top deburring guys in all of Los Angeles ruined over 100 picks of mine -- over $3000 in sales. They were warped horribly.

    I have one other jobber I may go back to at some point.

    thanks,
    scott

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    Quote Originally Posted by cyanidekid View Post
    Have you tried a rotary or polygonal rotating type tumbler instead of a vibratory type? It should run cooler and may make dry running possible. (Viking brandis an example of the latter)
    Cyanide, thanks. Mainly cost. I've literally spent probably $1000 or more just on tumblers, and I'm not wanting to invest more until I get closer to a solution. I tried a BUNCH or the Harbor Freight units, both vibe and rotary, and they were, uh, crap. So now I'm using vibe units mainly from Raytech and Lyman.

    I think if I have a fluid in there, it will cool the batch enough to avoid the heat and warping.

    Thanks So Much,
    Scott

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    Quote Originally Posted by Tyrone Shoelaces View Post
    Me too Larry, one that allows me to play the guitar with no musical ability whatsoever. Just a little bit, I'm too old to be the next Jimi but playing like Eric would be OK.

    Sorry to interrupt the thread.

    Regards Tyrone.
    Guys, I have no musical ability, but that never stopped me.

    sm

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    IMHO diamond is a shit abrasive for plastics, diamond cutting tools, hell yes, but as a abrasive, the grains just are not sharp enough edged to naturally abrade plastics well. Think you would do far better with finer crushed glass grit made from bottles commonly used in grit blasting to remove paints, its naturally sharp and will cut the work far faster than most other abrasives. Garnet or similar is what i would try. I would not bother with the plastic media, your parts are too soft, the media will wear smooth - won't break down enough to stay sharp, ceramic media may be better if you can get a compatible friablity so it does stay sharp enough to keep cutting.

    Kerosene is one option, but you need a really thin liquid or your going to take all the particle energy out and soften all the impacts you need to do the actually cutting.

    You say tumbling but then say heats a issue, what are you using as a tumbler, you may do far better with a old slow cement mixer type tumbler that you know actually tumbles the stuff. Drop the speed low enough to get good action and such that you get no heat build up, yeah its slow as in days - may be even a week to work through a few grits, but its as near a zero operator effort as you can get. Time is almost always your friend when tumbling stuff. Its a naturally slow process the trade off is the zero operator effort.

    Other option is look as some of the abrasive brush finishing options, simple vacuum fixture and a slow pass through, keep the brush speed down to keep the heat under control. Can then repeat to polish too, secret when working plastics is to limit heat and to do that you generally have to go slower, that said you can kinda compensate for that by cutting faster and harder with more aggressive abrasives.

    If you were not after the edge rounding you naturally need, i would be looking at a simple wide belt sanding jig.


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