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David Kahn

Demagnetizing an Anvil

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I have a new, cast steel 240 lb anvil that is pretty strongly magnetic.  Tools and such stick to the anvil face. 

Has anyone else run into this issue?  Is there an easy way to demagnetize an anvil?

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Think the horn'll point north if you float it? I've never heard of an anvil that strongly magnetized, have you  talked to the maker?

Failing that, we used AC magnetic yokes to magna flux drill steel and they'd demegnatize almost anything. Perhaps wrapping a long extension cord around it and running a motor or even light will do it. Failing that, (I wouldn't be surprised) an AC electromagnet should do it though I don't know if it'll need to be a ring around the anvil or not.

Frosty The Lucky.

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Mr. Kahn,

Would a deguasing cable set-up work?

They were used to de-magnify the hulls of ships during World War Two in order to counter magnetic sea mines.

SLAG.

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As far as welding cables being wrapped around it, the polarity matters. If AC is the polarity you want, then by all means wrap your work cable around the waist several times and run some weld bead somewhere that needs it. B)

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Being a new anvil I assume (guess) that the manufacturer checks the cast for craks using Magnaflux (Magnetic particles inspection or non destructive something or other.) 

Probably too cheap to afford a proper testing method. 

We used to test marine crankshaft for cracks using a strong current like the one from a large welder, wrap the DC cable around the piece and then run some fluid loaded with very small steel filings over it. Using UV light or some other green light (It was a long time ago) you could see the crack because the magnetic field created in the shaft was interrupted by the crack and the filing would stand up instead of lay flat giving away the crack.

The unintended consequence of this method was that the shaft would be now magnetic. No big deal for crankshafts as far as I know. 

Now  considering our recent conversation about magnetic fields and rebound, this could turn to your advantage if you can magnetize your hammer in a way that you hit the north pole with a north pole. Infinite rebound!

Nee only kidding.

Don't worry about it. With normal use, as you strike the anvil the steel molecules will suffer disorganisation at each hammer stroke and lose magnetic field. At what rate i don't know, but one way do demagnetise is hitting the object with a hammer because magnetism requires all molecules or at least the majority to be aligned. A hammer stroke will do the opposite

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Sounds like a way to coat your anvil with scale and grinding residue---Furry anvil!

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7 hours ago, Marc1 said:

Being a new anvil I assume (guess) that the manufacturer checks the cast for craks using Magnaflux (Magnetic particles inspection or non destructive something or other.) 

Probably too cheap to afford a proper testing method. 

Good input all around by Marc.

I would add that magnetic particle inspection can be quite a good test method for cracks and other flaws (including some near-surface defects that penetrant inspection won't find). The "too cheap" part comes in when they didn't demagnetize the anvil after inspection. It would have taken only minutes.

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22 hours ago, SLAG said:

Would a deguasing cable set-up work?

Yes, if you have access. An AC magnetic field will demagnetize without having to worry about polarity. I have/had(?) a mag/demag ring in my toolbox, slide it over a screw driver and it magnetizes it, reverse it repeat and it demagnetizes. 

On the North slope we magnafluxed drill rod with AC yokes to prevent magnetizing the drill strings. You want cuttings to flow up with the drill mud, not stick to the rod and grind it or the casing. A magnetized drill string magnetizes the well casing so ferrous or magnetic rare earths stick.  One pass of an AC yoke demagnetized entire tool boxes.  They killed wrist watches, electronic or mechanical, instantly from about 6" or so. I wonder how smart phones like them. 

Frosty The Lucky.

 

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Used pipe and sucker rod from the oilfield some times come up magnetized (radioactive as well) and welders wrap their leads around it and weld it up into beutiful pipe fence. I imagine a little experimentation will tell you wich polarity you need to fix it.

 

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Though my anvil is not highly magnetic like yours, I have a really weird anomaly of magnetism.  There is a "ring" on the face which is magnetic where no other area is.  Basically, it looks like the ring a coffee cup makes that your wife is always screaming at you about using a coaster regarding...slightly smaller and more like pop can sized.

Perfect circle that picks up magnetic slag where no other area on the anvil does.  It's not a disc area...it's a true ring of magnetism. 

I had intended to bring it up as a mildly interesting phenomenon in a post sometime but keep forgetting to take photos.

Try and degauss using an AC welder as others have said.  If you don't have that available, try a long shop extension cord (heavy cord that'll handle the amps) and plug in something like an electric heater to heat up your shop area...and just leave it wrapped/on for a day.

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My Fontanini (Rat Hole) came moderately magnetic, I intended to degaus as described above but never got around to it.  Hammered on it hard for 5 years or so and it's not so bad now.  It was kind of fun knowing when my workpiece cooled thru the Curie Point.  

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