DIY Demagnetising tool that works

[Mark Presling]

Tony,
I am glad it worked for you. Mine gets a regular workout. For some reason my shed seems to have a magnetic charge. I have heard that a nearby lightning strike can magnetise large structures. We get lots of thunderstorms where we live and we had a very close strike a few years ago that killed the quartz clock mechanism in our kitchen!
Regards,
Mark Presling

[Beserkleyboy]

Congrats, Mark! Just btw, where are you that you get the lightning? Cheers
Jim on a beautiful early winter's day (23°C) in South Coast AUS

[tonyfoale]

Tony,
I am glad it worked for you. Mine gets a regular workout. For some reason my shed seems to have a magnetic charge. I have heard that a nearby lightning strike can magnetise large structures. We get lots of thunderstorms where we live and we had a very close strike a few years ago that killed the quartz clock mechanism in our kitchen!
Regards,
Mark Presling

Lightening can be destructive. A couple of years ago it destroyed the controller in a pellet fire heater as well as some UPS and other things. I made a new controller for the fire from an Arduino which works better than the original.
I use a some magnetic bars as tool holders and that is one reason that I sometimes need to demagnetise. When I saw your idea I knew that it would work but I was uncertain as to whether it would work well enough. It has proven itself on calipers, drill bits (I don't know how or why they get magnetised) and most screw drivers but I have one screw driver that refuses to be demagnetised. I wonder whether it is intended to be magnetised and perhaps has a magnet hidden in the handle. It is not strongly magnetised but it just will not give up what it has.

[mklotz]

For bigger tools, I demagnetize with a bulk tape eraser (remember those?). For smaller tools I use my old Weller soldering gun.

However, when I saw Mark Presling's ingenious mechanical demagnetizer...

DIY Demagnetising tool that works

I had to have a miniature version for my in-house small job bench. Beyond its undeniable coolness, it would save me the trip to the garage to retrIeve the soldering gun and could be spun with any of the Dremel/Foredom-like tools lying on the bench.

I was fortunate to have some 1" fender washers with a 1/8" hole that just fits a 5-40 screw to provide a shaft to grasp in the Dremel. Six Harbor Freight 5/16" diameter super magnets were epoxied to the washer in an alternating polarity configuration.

Spun at even a low speed, it does a fine job of demagnetizing small tools.

[tonyfoale]

It is now 3 years since I made my version inspired by Mark's. I made a stand alone version with the rotor driven by an old washing machine pump motor. The motor and switch are encased in a plastic junction box and sit on a bench permanently. It gets used regularly. I am still at a loss to understand how calipers get magnetised but they do, although not often.

[yair feldmann]

Nice idea! This is my 2024 3D-printed version. Since it is plastic I don't have to worry for the magnetism of the stem.

[yair feldmann]

Only after posting my thread did I notice that there was another one, containing a 3D file of this tool. Great minds think alike... Magnetising and demagnetising tools.
I happily adopted his concept.

[tatoga]

THANKS EXCELLENT. WILL BE VERY USEFUL

If you are like me, you can get sick of tools like screwdrivers, scribers and allen keys that pick up swarf because the tool has gradually acquired a magnetic field. I purchased one of those little demagnetising tools that have a kind of staircase opening inside a plastic housing but was disappointed with the almost non existent effect on the tool. I wanted to build something better but I also didn't want to use anything like a modified transformer since they looked a bit scary. What I came up with was a device that can be used in the drill press, lathe or even a cordless drill. It uses four rare earth magnets with alternating pole orientation which can be spun so that the magnetic field is rapidly switched in the presence of the tool. All you have to do then is to slowly withdraw the tool from the effect of the spinning magnets. That's it!