Demagnetizing a Screwdriver

these days, tool companies have found that a lot of people like the handiness of magnetized screwdrivers, so its sometimes hard to find a good set that isnt magnetized. but for some things, such as replacing sensitive electronics like hard drives, its necessary to have a completely demagnetized screwdriver. in this instructable, i'll show you how to demagnetize a screwdriver with heat.


Step 1: Materials

its simple. all you need is a (magnetized) screwdriver, and a heating element. i used an electric stove, but a gas stove, blowtorch, or gas welding torch would also work

Step 2: Start Your Heating Element!

get your element nice and hot. for electric stoves, turn it up all the way. for gas, turn it up so the flame is about an inch long. for a blowtorch or welder, choose your own setting. a little

interesting fact: hot metal (and in this case, ceramic) gives off infrared light, which can be seen by most modern digital cameras. on such cameras, it actually appears as slightly blue or purple, which is why the burner looks pinkish purple in the picture.

okay, so your element is started, now for the fun! you want this to get nice and hot all over, so you need to lay the blade of the screwdriver across the burner in such a way that it touches as much of it as possible, without the plastic handle being too close and melting. i achieved this by propping up the handle with a steak knife, and laying it across the burner, though if you have an open flame, it may be best to point the screw driver up and tilt it into the flame, so its all in the flame.

Step 3: Wait

you need the screwdriver to be very hot for it to lose its magnetism. somewhere around 700°F this temperature is called it's Curie Temperature. however, prolonged exposure to smething really hot will cause it to lose magnetism slowly, so you do not necessarily need it to reach this temp. when you heat up the screwdriver, it will start losing magnetism. but it will also change colors. this is a property of metals, and comes in handy here. first, the steel will turn a straw color, then progress to a bluis color, then to black, then it will form a whitish coating, then it will glow. by the time the tip is a whitish color, all the magnetism will have left the screwdriver!

Step 4: Temper/cool

this step is optional. once you have heated it, the magnetism is gone. but its still hot right? well in this case, you can do what we call tempering. this hardens the metal so it wont bend or disfigure when you use it, likely making it last longer. for this, you need a basin of water large enough to hold the screwdriver's entire blade, with you being able to hold the handle.

first, dip the screwdriver in the water for just a moment. the water will hiss and steam, and the screwdriver will tremble a little bit. you have to pay attention close here, as the heat can make the driver very brittle and might break. you want to wait for the bluish color of the driver to move towards the tip of the driver. when it has, you want to dip the driver in the water and leave it until it stops hissing. wait a few seconds, and the screwdriver will be the same temperature as the water, and cool to the touch. congratulations! you have demagnetized and tempered your screwdriver! if you want, you can use sandpaper or wet aluminum foil to scratch the blade of the screwdriver so it will be shiny again, but this is completely optional.



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    7 Discussions


    3 years ago on Introduction

    Or use one of these to keep the temper of the tool (don't trust a random time dunking of metal at unknown temperature) - and keep the look of the tool as well :)

    When you need it magnetic, a few strokes in the right slot is all it takes and the other slot demagnetizes it just as quickly.

    While you shouldn't use a magnetized tool inside e.g. old clockworks, it won't harm a hard disk drive to use a mag-driver near it! You need quite a lot of magnetic force to damage an HD from the outside - trust me I've done it on purpose and it took a huge stack of magnets (around half a meter of stacked ceramic (but very powerful) magnets.


    8 years ago on Introduction

    I don't understand why you would need a demagnetized screwdriver for hard drives. Hard drive has some of the strongest magnets inside the case, they work by using magnets dont they?

    3 replies

    you go ahead and use your nice magnetized screwdriver to switch out your harddrive... i bet the cost of the harddrive youll be SOL. they use magnets, but those magnets are placed very precisely. the platters of a harddrive have memory stored in them magnetically. to "flip bits" the internal magnetized head goes over them. getting another magnet close to a harddrive will not only erase it, but also destroy it.

    but such a weak magnet like a magnetic screw driver? With the screws on each corner, and now actually immediately close to the discs, it couldn't do THAT much damage to it, surely

    Phil B

    8 years ago on Introduction

    Sometimes a magnetized tool is an asset. A screwdriver can hold a screw on its tip while trying to install it down a hole in a constricted area. Sometimes a magnetized tool is a pain and you want it demagnetized. I have some pliers and screwdrivers that have become magnetized and wish these were not. Although I no longer have it, I once had the frame of an old electric motor from a junk garbage disposal. I could connect it to AC line voltage and quickly dip the tool into the center opening a couple of times. It was demagnetized without the need to restore the temper of the tool's steel. (I did not want to leave the motor frame plugged in for more than a few seconds. It overloaded circuits fairly quickly.) I no longer have it because the windings eventually failed.

    1 reply
    Phil BPhil B

    Reply 8 years ago on Introduction

    After thinking about your Instructable, I decided to try a demagnetizer for cassette audio tapes to see if I could demagnetize my screwdrivers and pliers. It works very, very well. The demagnetizer is something I bought in the late 1970's at Radio Shack. Hold the magnetized tool near the underside of the demagnetizer and use the thumb to energize the demagnetizer. Move the tool away from the demagnetizer in an orbital motion. Release the switch with the thumb. This item is no longer in Radio Shack's stock, but you might be able to find one on eBay or at a rummage sale.

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