Salvaged Coil Magnetizes Tools On Demand


When working in hard to reach areas, magnetized tools can mean the difference between wrapping things up quickly and spending way too much time blindly grasping for dropped screws. [Damir] wrote in to share a handy little contraption he built which allows him to magnetize and demagnetize his tools as needed.

While rubbing a magnet against the tip of a screwdriver will impart a weak and temporary magnetic field, he felt that a stronger more permanently magnetized tool was far more useful. It is pretty well known that subjecting metal to a direct current magnetic field will magnetize the item, and an alternating magnetic field will demagnetize the same object. [Damir’s] wand will perform either task with the simple flip of a switch.

He salvaged the motor coil from a broken washing machine and mounted it in a project box, along with a single-pole changeover switch. A small diode is used to perform rectification on the AC input, providing the DC current required for magnetizing his tools.

Every once in awhile we find the need for magnetized tools, so we think this would be great to have around the workshop.

Check out a quick video demo of the magnetizing wand after the jump.


23 thoughts on “Salvaged Coil Magnetizes Tools On Demand

  1. I needed that thing so ******* much just yesterday as I was trying to mount a new “strip” of power outlets (built into an industry type plastic box suited for those) under my desk …. I was fumbling with the screwdriver and had already searched the house for any neodymium magnet to connect to it…

  2. That’s neat. I like that.

    I keep an old hard disk magnet on hand for this job. They have a pattern of N-S stripes widthwise, so quickly drawing a screwdriver along the long edge will demagnetize it a bit. Not nearly as effectively as this device though.

  3. @Compukidmike
    It’s easy to get rid of metal shavings, just whack you screwdriver against a hard surface.

    personally i don’t see the point in demagnetizing the screwdriver again , but still this tool seems like a fun project to do.

  4. also if your goal is to strongly magnetize a screwdrivers tip an improvement may be to add a silicon steel plate to the top and bottom part of the coil with the top plate having a small hole so you can poke your screwdriver in it. this will create a much easier path for the flux to travel and guide most of it through the screwdriver resulting in about 10 – 100 times greater flux density in the screwdriver an overall stronger magnetization

  5. Magnets…how do they work? You can’t explain that! :D

    @Password: What if you want to (un)screw something that is sensitive to magnetism? There is your point in demagnetising said screwdriver.

  6. @Nomad:
    As with many things I don’t think that its a case of how magnets work but more a case of why (:
    It’s a nice feeling to me that there are still fundamental things in the world yet to discover (: I would hate to live in a world were I could never get famous from making a scientific descovery (:

  7. Did anyone see the mistake on his page? :)

    I made something like this, but for some 8mm data tapes I had to erase (about 6500 of them, whew).

    Didnt think of this! I’m still using my $3 block from Sears (not all that much).

    Great demagnetizing tools when you work near live circuits sometimes. Dropping one can be disastrous (yes, even insulated tools, all I use when there’s any power nearby. Klein.

  8. Neat project, and I am going to be looking in the recycled appliances area for some coils.

    NOTE: This project uses a 230v coil, not standard for North America.
    Other suggested coil sources from the link may not work here.
    The NA microwave tray rotator motors are 18-24v, IIRC. (But while you are in the microwave, don’t overlook that nice high voltage diode. Might be covered in shrink tubing, so look sharp.)
    Voltage on a washer control rotator motor…Hmm.. Will get back to you tomorrow. Should be 110v and easy to modify for this. Dishwashers and dryers have a similar motor in their timers, so there are many sources. :)

    I really want one of these in my toolbox. :) Gonna be scrounging parts tomorrow at work.

  9. Nice trick, I am SO building this at work tomorrow!

    @Everyone who is worried about 110/220v differences: This will work on a lower voltage, it will just need more current. It would even work on 24v AC if your wires were beefy enough. All this is is an air/sometimes air+iron core inductor.

  10. ……….if you use a 220 volt motor on 110 ac(when using it as a coil)
    higher internal resistance means it will use LESS current as it was made to use a higher voltage, it uses longer wire of the same diameter
    also the tray motors in microwaves are indeed 120 volt gear motors so they would work great for this
    when i read this i was all like “wtf, washing machines use big open cage motors! how big is that enclosure???”

  11. “I’ve always used magnets to magnetize some of my tools but never wondered how to demagnetize them.”

    Whacking it against something hard, like an anvil, will re-align the magnetic domains back to random.

    It doesn’t work so well with tools that are made magnetized, because they are made of a magnetic alloy that would take a whole lot of whacking to get completely randomized again.

    Another way is to heat the metal. It is possible to take something like a hard drive magnet, warm it up sufficiently so it loses its field, and then remagnetize it with a sufficiently large jolt from a coil. It works best if you heat it up and then let it cool down in the strong magnetic field.

    That way you can change the orientation of the poles in the magnet, if you need it for things like small DIY generators.

  12. Back in the day when through-hole was king and DIP pitch ruled uncontested, we used to solder using “soldering pistols”, not irons. Which were basically a 220V transformer with a SINGLE loop of copper bar as a secondary winding, and a short copper wire as a tip to complete the circuit.

    I don’t think I have to describe the kind of current that went through the “tip” if it could heat it up instantly when you pulled the trigger. Incidentally, sticking any magnetized tool in that loop demagnetized it pretty much immediately.

    The days of DIP are pretty much gone, but I still have the pistol… ;)

  13. …nor will “UL” or any similar product safety testing organization.

    Still, it’s a fantastic DIY tool. Simple, effective, and very handy. I’ll be adding it to my list of stuff I want to build. Finally a use for all the magnet wire I inherited. I’ll be trying to build my own coil instead of scrounging a motor.

    Only problem is the portability. You’re tied to an AC outlet’s range. Rather than rectifying AC to DC, I think I’d rather have it use batteries and invert it to AC, but that will be a lot more involved than this project. Maybe if it’s intended use is only around the home/workbench…

  14. @Frogz- Just got back from tearing apart a few (older-1988-2004) GE, samsung and kenmore(LG) microwaves. All the platter motors and mixing plate motors were 21 V AC. Well labeled.

    OLDER dishwashers, washing machines, dryers…if it has a knob that clicks there is probably an Eaton brand motor inside. If there is no knob,all buttons…probably solid state. No Motor :(

    I just pulled a few motors out of dishwashers and a washing machine control units, c1990~. Pulled the coil out of one…looks great! May pick up a project box from Radio Shack tonight..

    Got a few diodes out of the microwaves also. BIG and beefy. Free too. :) Forgot a cord, however…D’oh!!! One more trip…

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