Demagnetizing (degaussing) a tweezer?

[dzseki]

I have a vintage Swiss „Dumont #4” tweezer which I like the most. The only downside is that this was made from magnetising material and over they years it eventually gained magnetic force enough to make it difficult to work with SMD components.
From university days I seem to remember that materials can be demagnetized with a low frequency decaying magnetic field, this somewhat lines up what I’ve seen in old CRT TVs.
My idea was to pair a function generator with an audio power amplifier which would drive a coil near the tweezer, but I would be glad to hear some first hand experience on practical matters, any advice is welcomed.

[JackJones]

I've got a demagnetizer that plugs straight into the outlet. It's just a switch connected in series with an inductor. It does work very well, you could always try making one yourself it doesn't seem to be too complex.

The way it's used that you activate the switch while the item to be demagnetized is close to the coil. Then you slowly pull it further away from it while the coil is still powered.

Here's a video by Big Clive, that's the same demagnetizer I have. They're not too expensive, less than 10€.

[duak]

I made a small degausser from a 48 VDC telephone relay coil about 10 cm by 3 cm diameter.  It is operated from 120 VAC 60 Hz.  It has enough reactance to limit current  so it does not overheat.  Do not use an AC coil because it is designed to limit current only with a complete magnetic circuit.

I plug it into mains power and then run the pole piece over the tool.  When I get to the point of a screwdriver I pull the screwdriver away from coil with the mains voltage still applied.  The alternating magnetic field reduces as the two are separated.  To degauss tweezers or pliers I start at the hinge then move to one tip, then back to the hinge then to the other tip then back to the hinge where I pull the coil away.

[GLouie]

I have always had mains powered audio tape and head demagnetizers around, which work great for tools. Your idea could work, but you need an electro magnet - a ferrous rod inside a coil, and a lot of power, I think. Maybe more than you'd want to do with a typical audio amplifier and homebrew coil/magnet. My old Radio Shack tape eraser works great, but is rated for 120VAC and 8.5A, with a duty cycle of 1 minute on/30 mins. off!

A cheap audio head demagnetizer might be easier and cheaper. Wiha also makes a permanent magnet tool demagnetizer (400-10), but I have never tried one.

One might think that an unshielded transformer in an operating mains powered device might work. You bring the tool close to the steel part, see if it grabs magnetically, then pull it away.

[bob91343]

Back in the day there were tape demagnetizers.  Or degaussers.  I have two of them; they plug into the mains and you use them the way these posts indicate.  There are also devices called tape head demagnetizers but they are sort of junior size and not as effective, I think.

Originally you would put a reel of tape on these things (there was a post just right for the reel hole).  Rotate the reel slowly and then gradually lift it off the post until you had it at arm's length away from the demagnetizer.  Worked great, and works great for tools as well.

I don't like using magnetized tools.  I don't have enough control with them.  Occasionally I need to put a screw through a hole that is a long reach, and that's about the only time I use a magnetized screwdriver.  I have also used some sticky tape or even considered chewing gum but I don't chew gum.  Once used, I demagnetize the tool.

[RoGeorge]

You will need strong alternating magnetic fields decaying down to zero.  I'll say impossible to achieve with an audio amplifier.

Much simpler is to put a coil on a strong AC transformer.  That will create the alternating field.  To make it decay slowly, you just slowly get away from the coil, i.e start with your magnetized tweezers near the coil and slowly move it away during 5-10 seconds.  The idea is that at each field change the magnetic hysteresis will became smaller and smaller, because you get away from the coil, until you get so far away that the remnant magnetization will be zero.

Even simpler if you have a soldering gun:



details here https://www.eevblog.com/forum/testgear/a-look-at-the-uni-t-ut210e/msg1409125/#msg1409125

[dzseki]

Thank you guys.
I have some stupid amplifiers even capable of 8A continuous output current, but yeah using a modified solder gun looks much simplier

[bob91343]

That solder gun looks dangerous.  You may end up with serious burns unless you use more inductance.  You don't want the thing to get hot.

I wonder how a degaussing coil from an old CRT monitor would work.  Those things demagnetized the tube and accessory parts every time you switched on the monitor.  They had a few dozen turns of small wire and got energized for a couple of seconds with a decaying voltage from 60 Hz.  I suspect the field wasn't strong enough to overcome the residual magnetism of steel tools.

[Bud]

In some cases the tv loop was not strong enough to demagnetize the screen. I once had a Sony technician to come and use an external demagnetizer to get rid of a big red area on a brand new TV i bought. Apparently the store had the TV stored in the warehouse near a big ass speaker or something so the screen developed a magnetized area that could not be removed by the built in loop.

[pardo-bsso]

I made mine using the transformer of a small UPS with a parallel R-C and a push button. I removed the core laminations and only kept the E parts.

I feed it with a laptop supply and upon releasing the button I have a nice decaying field.

As an added bonus, it helps to clean up the floor when doing machine work.

[jmelson]

If you have a Weller-style soldering gun (transformer type) pull the trigger, then pass the tweezer completely through the loop of the soldering tip, and then a foot way before releasing the trigger.  It only takes about 1-3 seconds, and will demagnetize tweezers for several months before they get magnetized again.

Jon

[Psi]

I've demagnetised screwdrivers on occasion as needed.

I grab a big electromagnet, run it from AC and hold the screwdriver to the energized magnet.
Then i remove it slowly until it's arms length away and switch of the magnet.

Works great.
It just has to be AC and you have to remove the object slowly before turning off the magnet.