Yet Another DIY - Handheld - Small Tool Demagnetizer

[Be_Zero_Be]

I didn't want to hijack another thread about DIY Demagnetizers so I started this one.

Every once in awhile I have an idea that actually works.
One thing that I find annoying is tools that become magnetized for one reason or another.
Screwdrivers, Pliers, Drill Bits, etc. …
I wanted a simple CHEAP demagnetizer.
All I needed was a magnetic core, a coil and an AC voltage.
Here is what I came up with.
I used a motor from a fan.
The one I actually used is from an old microwave oven.
The one in the pictures is from a bathroom exhaust fan but is identical.
I simply removed the rotor assembly and the core copper (optional).
I hooked up a momentary pushbutton switch and a pilot light (optional) and a power cord.
I used a polarized cord and put the pushbutton switch in the hot side of the power cord.
I mounted it into a plastic box and that was it.
IT WORKS GREAT.

To use it, energize the demagnetizer.
Bring the object to demagnetize to the demagnetizer.
It is OK to let the object come in contact with the demagnetizer.
Withdraw the object from the demagnetizer at least 12” before de-energizing the demagnetizer.
This will prevent accidently re-magnetizing the object.
I have demagnetized screwdrivers, pliers, drill bits in a matter of seconds.
I even completely demagnetized a Model T flywheel magnet.
It is small enough to be handheld so you can bring the demagnetizer to the object.
Words of caution :
Use a momentary pushbutton switch only.
Make sure the motor you use is rated for the same voltage you plug the device into.
Make sure all electrical connections are solid and safe for the operator.

Be_Zero_Be

Photo-1
Fan motor salvaged from an old bathroom fan.


Photo-2
Make these modifications to the motor.


Photo-3
Cut the pole piece as shown.
Be careful not to damage the windings.


Photo – 4
The final product with momentary push button and optional pilot light.

 

[Rooster]

I used the same thing a year ago except all i did was remove the rotor, didn't cut anything, works great.

 

[Be_Zero_Be]

My first version was with the pole not cut as above.
A friend suggested that I cut the pols as above.
The object will complete the magnetic circuit and improve the performance.
It has worked well both ways.

Be_Zero_Be

 

[benmychree]

When I worked in the machine at the Kaiser Steel Corp. in Napa Ca. we had a demagnetizer that was nothing more than a field coil for a DC motor generator arc welder, it had a hole through it about 3" X 4" and was wrapped with cloth tape and "doped"; all it had for an on/off was a cord plugged into 110V; to use it, we just plugged it in and passed the object in and out through the core several times and unplugged it, just that simple.

 

[hman]

Be-Zero-Be: I really like the way you opened up the pole piece ... allows you to demag larger items!

I built a mag/demag a wile ago, using a different kind of motor stator, and fully enclosed it in a plastic housing. Then I bought a bunch of PTC devices (originally intended for color TV degaussing) and stacked them in parallel until I had sufficient current to get good demagnetization. Then the current smoothly drops to zero in about a second. No need to worry about slowly removing the item. To magnetize something, I just blip the switch. See post #109 at https://www.hobby-machinist.com/thr...ntrol-circuit-wanted.57733/page-4#post-489158

 

[f350ca]

Thanks for the post, will have to build one.
Its odd, things in the shop will suddenly be magnetized then eventually go back to normal. But a pain to use when cuttings are hanging to the drill bit or what ever.

Greg