Demagnetizing steel shaft

[tcmtech]

You sure that's not much oil making the dust stick tcm?

Yea their clean! I am not that dumb! They were engine cleaner washed and blow dried with clean air. I know the difference from a magnetic beard and oil surface tension.
Magnetism is a natural occurrence in iron. Some iron alloys just show it better!

And the only thing my personality seems to be magnetic to is children, animals, and emotionally unstable women!

 

[d0ugparker]

DIY: Quickly demagnetizing my shop vise

The pads on my shop vise were so magnetized
that they'd hold on to all the shavings I was
cutting. I had to demagnetize it, the magnetism
was so strong that blowing strongly at it wouldn't
clear the debris.

What I just did was to plug in my soldering gun,
hold the gun near the pads, hit the trigger, and
while running the gun slowly along the length of
the pads, I tapped the pads lightly with a hammer.

It's the coils inside the gun that are being used,
not the tip of the gun--the tip's just getting hot.
It's the coils that are generating the EMF that's
helping with the demagnetization.

Two minutes later, the magnetism is gone. I'd
guess the harder you hit with the hammer, the
quicker you'd get the job done.

The caveat would be that sensitive items like
bearings and anything with electronics in it (and
many other items, of course) would have to be
investigated and treated gingerly or not at all,
or in the case where strong EMF could destroy
the item.

Be careful out there...

Doug Parker
Orlando, FL
USA

 

[Hero999]

It's got nothing to do with the coils inside the gun.

Heating the vice and subjecting it to a mechanical shock removed the magnetism.

The field generated by the heating coils would be minute because the wire is not coiled round a ferromagnetic core which concentrates the flux.

 

[Sceadwian]

Hero, in this case the vice itself is the ferromagnetic core, it's just outside of the coil =) Not the best place for a 'core' but it will still concentrate the flux. It was probably a mixture of everything, if you want to disprove the theory of operation you'd have to repeat the entire process excluding one and only one of the things you did to the vice and provide measurable results. You can't say that he's wrong if you didn't prove that he's wrong experimentally, you're just arguing pure theory, as you don't know how much heat was actually applied to the vice, how strong the field actually was, or how much force was actually used in the hammer blow, let alone what type of material the vice is made out of or the type of soldering iron construction he has.

His method worked for him, he was simply presenting that. Others can judge for themselves who what where when and why, but it's rude to simply state without proof that one specific portion of the equation wasn't part of the factor.

 

[superfrog]

Many gearboxes have a resonably strong magnet at the bottom of the casing to keep metal shaving from flowing all around the place wreaking havoc. My old faithful till the end Peugeot 305 GT had such a magnet, I never had gearbox problems (well it did loose front brakes in the end, but nothing to do with gearbox). My mother's astra has a magnet attached to the oil filling cap that collects shavings, and despite her driving the car for 200K miles, the gearbox is fine and I do not believe it needed a single oil change. I do not own the haynes manual for my focus but I would not be surprised for such a magnet to be present.

Maybe you could adapt something like that as a solution to your metalic particles problems. A small rare earth magnet would probably work nicely if it can be placed somewhere where it doesn't interfere with gears and is not in a high oil flow zone where shavings could be picked up again by oil flow. Metal should be removed from the shaft trough centrifugal/oil friction when rotating so should not stick to the shaft too much.

 

[d0ugparker]

It's got nothing to do with the coils inside the gun.

Heating the vice and subjecting it to a mechanical shock
removed the magnetism.

There was no heating of the metal. I re-read what I wrote
and that wasn't clear. What I meant to say was that although
the tip of the gun got hot, it wasn't used to heat the metal,
and that that heating didn't play a part in the process.

So I agree that the mechanical shock was part of what
did the trick. Since heating wasn't involved, I have to
believe that the proximity of the coils inside the soldering
gun to the vise pads contributed to the final reduction of
the magnetism. It would make sense since the EMF was
changing as I moved the gun past the length of the metal
pads.

The field generated by the heating coils would be
minute because the wire is not coiled round a
ferromagnetic core which concentrates the flux.

IANA physics major, so I can't attest to the strength
of the fields outside the coils vs. at the center of its
windings, but since there's enough EMF to move the
shavings around on the surface of the vise, I have to
believe any effects from the EMF of the soldering
gun on the metal pads of the vise--even if it were
small--would still help the overall process.

Or, could I just have just omitted the soldering gun
and simply whacked the pads with the hammer and
accomplished the same thing?

Doug

 

[Hero999]

I would have thought that the coils would have been designed to radiate as little external magnetic field has possible, in order to comply with the EMI regulations.

Maybe it was purely the mechanical shock?

 

[shortbus=]

There are many Google hits on this. Here is one of them; https://www.wikihow.com/Degauss-a-Computer-Monitor

 

[Sceadwian]

Hero, the OP is talking about a soldering gun, those aren't really designed for sensitive electronics work in the first place, they're designed to get hot fast for big soldering in general. Also as far as the EMI rating of a soldering gun goes that's more about the voltage developed at the tip, which if I'm not mistaken soldering guns are not know for generally having grounded tips.

 

[tcmtech]

A transformer type "Buzz Gun" generates a considerable amount of external magnetic field. Put one near a magnet or iron and it will easily vibrate it from several inches away.

 

[Hero999]

There are many Google hits on this. Here is one of them; How to Degauss a Computer Monitor - wikiHow

IT appears that I'm wrong.

Let's get this straight, we're talking about a heat gun, not some kind of exotic eddy soldering device?

If so I'm very surprised that it produces enough of a field to degauss a monitor or vice. I'll have a play with my heat gun and some iron filings. This should also work with a hair dryer too.

 

[Sceadwian]

No, not a heat gun Hero. A soldering gun...

Just like that. A hair dryer would probably not work the coils are designed completely differently, the coils are much bigger and air wound the stray field they put out is probably very week even though the power is higher, also they way air heating coils are wound I don't think the field is going in the right direction. as tcm suggested it's really easy to determine the relative strength of an AC magnetic field, just take a strong permanent magnet and put it near the spot you're interested in. You'll feel a vibration from the induced forces in the magnet, the stronger the vibration the stronger the field.

I noticed this effect myself at work a long time ago and was surprised at how strong it was. I got one of the magnets we use to hold paperwork to a board near the forklight battery charger wire and thought for a split second I was about to get electrocuted. Although a bit higher than a typical soldering gun there's 20-30 amps of current going through the charger when it's on and you can feel the buzz in the magnet from almost 8 inches away. Since heating coils are typically wound and a soldering gun is designed to be compact the smaller field is magnified.

As a side note any even half assed decent CRT monitor made in the last 10 years should have a built in degaussing coil. I've yanked a few out of monitors I've disassembled, not sure if I kept any of them but they might run on straight wall AC power. The coils are pretty large would make a nice little project for a shop de-magnetizer, just keep in mind they're not meant for constant use, they generally get 5-10 second pulse of current when the monitor turns on, and sometimes you can activate a degauss feature in the settings. Just be careful, outside of the monitor and close to your person if you carry your wallet with you it will eat credit cards for lunch.

 

[Hero999]

So there's an internal transformer and the tip is heated by a very high current?

I see what you mean, I was thinking of a heat gun, I've got no doubt a soldering gun will work.

EDIT:
https://en.wikipedia.org/wiki/Soldering_gun

 

[Sceadwian]

I'm not sure the actual voltages used in a soldering gun like that, but I'm guessing it's low voltage high current to reduce the possible voltage applied at the tip.

 

[Hero999]

Did you read the Wikipedia article?

Here's a picture of the inside of a soldering gun.
**broken link removed**

 

[Sceadwian]

Yarp, looks like high to low voltage to me. For a second I thought that input coil was fine wire, then I realized it was actually a single copper band.

 

[gary350]

Most machine shops have a demagnetizer. It is 120 volts AC. The trick that makes this work is to put the metal part on the demagnetizer, turn it on, and remove the metal very slow away from the demagnetizer. AC continiously changes the direction of the magnetic field and as you move the metal away from the unit the magnetic field gets weaker and weaker until your far enough away that the magnetic field no longer has any effect on the metal.

I built my own demagnetizer at home it also works great to degauss your TV and computer moniter. I used #24 enamel coated copper wire to wind a pancake coil that is 1/4" thick 5" diameter. You have to apply polyurethane varnish as you wind the coil this glues all the wire together and stops vibration and AC hum. The coil is probably very close to 1000 turns of wire. I connected 1 end of the coil to a light fixture then I connect an electrical plug to the other coil wire and the other light fixture wire. I put a 100 watt light bulb in the light fixture. The light bulb acts like a resistor it limits the current in the coil to 100 watts. Plug in the electrical cord the light buld and coil are in series. You can make this be any power rating you like by changing the light bulb to a different wattage. If you want to degauss your TV or Monitor use a 40 watt bulb.