[Jewelry making - Article 00074] - [Orchid] How to Build a Magnetic tumbler

[John Donivan]

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    I can't offer measured drawings and the like, but here's how you do
    it. You need: 

    1) "Washing machine" motor of 1725 or 1750 rpm. 

    2) 5"-6" aluminum sanding disk, like lapidaries use, with a shaft
    size to fit motor. 

    3) 1/2" plywood or particle board circle the same size as the sanding
    disk. 

    4) 4-Neodymium Iron Boron disc magnets 3/4" or 1" diameter by 1/2"
    thick. 

    5) Wood for a box, various tools - a wood drill bit the size of the
    magnets, and a container for the shot and work. 

    I'll discuss the magnets later, but all you do is lay out the plywood
    circle very carefully so that you can bolt it onto the sanding disk
    on the exact same center. Then you drill it through in four equally
    spaced spaces to the size of your magnets, probably 1/2 way across
    the radius, or so the holes are inside the circle of the container
    you will use, bolt the wood to the disc, put the magnets in the holes
    - they should fit tightly, but I'd recommend a little epoxy for
    insurance. Then build a box out of plywood so the motor can be
    mounted shaft up, with a top made out of 1/4" plexiglass or heavy
    aluminum. You want the disc to be about 1/8" or 3/16" below the top,
    so the motor height needs to be adjusted accordingly. It's also
    useful to put some sort of brackets or wood blocks on top so the
    container won't walk - anything that will keep the bottom of it on
    center. Put your container on top, put pins, water, tumbling soap and
    work, turn it on and voila"! Magnetic Tumbler!! There are some issues
    - like heat dissipation, and obviously the balance of the rotor is
    important, which is your skill at layout and drilling, but I did that
    and used it for a few years. Neodymium Iron Boron (NdFeB or "Rare
    Earth Magnets") magnets are the most powerful magnets on earth. They
    are incredibly powerful, and the larger they are the more dangerous
    they are. If you got a big one and walked into the kitchen, knives
    would come flying at you. A very large one will alter a TV screen if
    you walk into the room. 1" x 1/2" ones are manageble, but they will
    pinch you real hard. If you got them apart, put your finger between
    them and nudge them till they jump -broken finger. If and when you
    get them, you'll see I'm not exaggerating. To get them apart, don't
    try to pull them, put one on a counter top and slide the next one off
    by pushing down on it. Anyway, you'll see, but don't take them
    lightly. If you buy them through channels, one 1" magnet might cost
    you $50. If you search EBay, you can get 4 of them for $20 or so. Get
    N38 or N40 if you can - that's the power rating. There are lots of
    dealers there, just search for "rare earth magnets" or 
    neodymium. And be careful with them.

    when you put the magnets on your rotor, alternate the poles - so
    you'll have, with 4 magnets, 2 North and 2 South.  That gives the
    swirling action.... 

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