Tool/Head Demagnetizer

By pishta, Nov 18, 2018 | |
  1. pishta
    This is an A/C electromagnet that strips induced magnetism from ferrous materials. Useful in demagnetizing screwdrivers, wrenches, feeler gauges, allen wrenches and any other small tool that doesn't need to be magnetized. In order for a tool to become magnetized, the tool can be stroked in one direction against a magnet. This, in simple terms, aligns the random polarities of the electrons all in the same direction. I have a large speaker magnet stuck to the side of my tool box and I wipe screwdrivers on it to attract small screws and nuts/bolts. When you pull the tool across the magnet, it magnetizes it. So how do you demagnetize a tool? You have to scramble the electrons back to their natural random order. This is done with another type of magnet, an A/C magnet that switches polarity 60 times a second, line voltage frequency. This will scramble most any induced magnetism in a ferrous material. We will use a bolt, a nail, or my favorite, a small screwdriver as its ferrous core. You will also need 30-50 feet of fine wire. I used the fine laquer insulated wire off the windings of a small DC motor.

    1. unwrap the wire off the motor, be careful not to break the fine wire. I let the motor hang and let it unwind itself with a bit of shaking. This keeps the wire somewhat straight. Or else, unwind it by hand but you will make a big twisted knotted mess if you dont manage it while you are doing it.

    2. leave yourself about 2 inches and start wrapping the wire in one direction around the ferrous core of your tool. Keep wrapping until you have a nice even wrap and the end is about 2 inches long.

    3. Use some sandpaper and carefully sand off the insulation until you see bare wire on both ends. Get out your multimeter and confirm continuity at both ends and no shorts to the core.

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    4. Now you need to find an AC/AC wall wort from a small machine. It needs to be A/C output or you'll just make another magnet. I found a tiny wall transformer from ? that was A/C 9V 300ma out. I think it was from some sort of charger.

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    5. Solder the lead from the transformer to the 2 legs of the wound wire. Verify that it works by plugging it in and see if it vibrates against a ferrous object, like a wrench. Once confirmed to work, wrap the tip and exposed wires with electrical tape or shrink tubing. no metal needs to be showing.


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    Wrap remainder of tool in electrical tape to cover any exposed wires. Your done!

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    6. to demagnetize something, hold the tool at arms length from the object and plug tool in
    (or turn on if you installed a switch) move tool into object and slowly go over length of object with tip of tool to scramble the polarity of the electrons. you don't need to touch it but you wont hurt anything if you do with the insulated end.

    7. when you are done, pull the tool away to arms length and de-energized the tool. this is important as if the tool is against the part when the plug is pulled, the tool may induce its last polarity back onto the part.

    8. This tool is mainly used to demagnetize tape deck heads and tape path. Use in same manner as directed but slowly wand all over the tape path, keeping it away from any magnetic media while it is energized. Do not have tape player turned on while doing this or you could damage your amp or pre-amp of the player with its pops from its strong magnetic field. It is recommended to demag your tape path after 100 hours of play, or up to 10 hours of play if you have a 3 head deck as those discrete playback heads do not get demagnetized by the A/C bias of the isolated record head like a 2 head player would.

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