Winding Magnet Wire Coil
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  1. #1
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    I hope this is not the wrong place to post this topic.

    I want to wind a coil using a 1.5 inch soft iron rod 8 inches long with 7.5 lbs of 18 gauge magnet wire (about 1800 turns). My intent is to make two of these so I can manufacture a magnet charger.

    I will use epoxy to keep the wraps from unwinding. I would really like to end up with a professional looking project.

    I have an under drive JR 9.

    Any Suggestions?

    Sherm

  2. #2
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    Sherm, I think it's a quite appropriate topic.

    I unfortunately can't give you much help other than that I know it's an intended use of the machine. I've seen mention of coil winding in SBL literature.

    I have seen a lathe used to wind a spring and I imagine it's a similar operation. You calculate a feed to use based on the wire size (basically the wire diameter will give you inches-per-rev). And then you need some kind of gizmo on the compound to run the wire through -- something like a needle eye as I recall.

    My suggestion would be to scour the old SB docs you can find to get a lead on what publication to look in.

    And please post your findings! I for one would be interested in it. A pic of a coil you make would be welcome too!

    Ken

  3. #3
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    South Bend had a special attachment for doing just that. Good luck finding one! I have done what you are proposing by runing the lathe in the sloest back geared speed and holding the spool of wire on a round shanked screw driver. I can not remember if I found it necessary to hold my thrumb on the spool to prevent a back lash. Gary P. Hansen

  4. #4
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    Hi Sherm - you still have an unread private message according to my machine

    18 ga wire is a tad larger than .040". Set lathe to cut 24 threads per inch. Need a combination guide/brake in tool post to put a little tension on wire. A slotted piece of hard wood with a clamp screw sounds workable - as long as you can apply some "grip" to the wire as it passes thru.

    How you want to effect the stop and reverse will be something you can play around with. Basically the spindle needs to keep going the same way and the reverse tumbler on left end needs to be used to reverse lead screw while half nuts stay engaged.

    Epoxy will be a mess but suit your self.

    You probably know you need to be using enameled magnet wire.

    You can get a little less than 70 feet wound on the first flight if you wind 7" long.

    John

  5. #5
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    dont bother with "threading" and the carrige, you can guide it on by hand far easier than messing with all that. --it's trivial.

    if they wire is kinked and you want a lot of tension on it to strighten it yank it stright a few feet at a time. or perhaps feed it through some cloth gripped with plires.

    keep the lathe running slowly and have someone attentive ready to stop it. it's easy to get yourself wrapped up.

  6. #6
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    Hi There,

    When my son and I were making a couple electro-
    magnets for a school project, we wrapped the
    core of the magnet with a layer of brown paper
    for insulation. A couple washers made of thin
    cardboard were epoxied on the ends. We were
    using a smaller diameter wire so a slight drag
    created by passing the wire through the fingers
    was enough to keep wraps tight. We set the
    carriage feed to approximate the diameter of the
    wire and just held our hands against the side of
    the tool post when wrapping. Spindle speed was
    set to the lowest back gear speed. The finished
    electromagnet was painted with varnish to seal
    it and hold the wraps in place.

    Good Luck!
    -Blue Chips-
    Webb

  7. #7
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    Two words for this:

    Foot pedal.

    Set the machine up with a foot pedal so
    you can stop rapidly if you get a mis-feed on
    the coil. Fourty thou wire is *huge*, I wind
    coils on the HLVH at work using seven mill
    dia wire, by hand often.

    You could also temporarilly turn your SB machine
    into a coil winder by driving the lead screw
    with a stepper motor and setting up microswitch
    or optical trips to reverse the carriage at the
    end of the travel.

    Jim

  8. #8
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    As others mentioned...
    1. go slow
    2. guide by hand
    3. Skip the epoxy
    4. Make sure you can stop it quickly
    5. Find/make the little tool that allows you to put proper tension on the wire as you wind. Be careful of this, I have heard you can remove your thumb/finger quite easily while winding thus in the immortal words of SB's HTRAL "spoiling your work" or thumb in this case.

    Lenny

  9. #9
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    I turn a lot of coils for antique scientific instruments I repair/reproduce. I have made round, squeare, oval, and all kinds of shapes.

    I make a bobbin to hold the wire in place.

    Usually use thin plywood or fiberboard. These endcaps keep the wire from rumming off the end (some coils I have made are 3" in diameter on a 3/4" core). Drill holes in the ends to let the beginning and end wire out. I use wax paper on the insides to keep things from sticking later on. I wind totally by hand to allow an even lay of the turns. That way I have total control over the winding and can easily back up if the odd turn goes wild.

    I seal the entire thing with clear lacquer (3-4 coats within an hour, let it soak in, and cure it for 24 hours in the sun (AZ has pleanty of that!)

    If you want a "core-less" coil (most of mine are on left-in-place brass tubing), use an expandable hand reamer coverd with several (7-8) layers of brown craft paper. The paper eliminates the hex shape the blades can impart and makes removal easier. Expand the reamer to max, cover with paper, turn BY HAND in the lathe, and when finished just back off the reamer to release the finished coil!

    This is not rocket science and does not need any power, other than good old elbow grease. Works perfect every time. I have made over 30 custom coils using the above proceedures using anything from 8 to 40 gauge wire.

  10. #10
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    Try searching among "Tesla Coil" builders. Many of these people wind there own coils, and you might find some pictures to go with the above advice. Most of which sounds pretty good.
    David M

  11. #11
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    Maybe you have already been down this road... But, just for the sake of arguement if nothing else, have you considered any of the electrical characteristics involved? Voltage, current, frequency if AC are all factors to be considered. Even the choice of iron core material makes a big difference in what this thing will do. If I read your post right you mean to build a device to magnetize stuff. If so you will be needing to use DC to run this thing. With DC your main consideration is the resistance of the wire and how much current will be dissapated in heat. If the current exceeds the current rating of a given size of wire it will melt down and short out. In normal situations 18 GA is good for about ten amps. Wind it tight on a coil and you trap the heat and thus greatly decrease the current carying capacity. Even at 2 amps you are dissapating a lot of heat that is trapped. I hope you plan on using a variable DC supply and are able to monitor your voltage and current. With DC it's simple, amps times volts equal watts. Even with DC the magnetic properties of the iron core will make a big difference in how effecient you rig will actually be. Even if your coil runs cool the poor magnetic characteristics of the core will make heat.


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