How to demagnetize my welding table?

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I'm getting tired of all of my tools getting slightly magnetized when I lay them on my slightly magnetized welding table.  I about went bonkers this afternoon trying to get steel dust off of my file - not sure why I suddenly became obsessive-compulsive, but I did for a few minutes.  So it's time for this to end if possible.The tabletop is 1" thick, 40" x 10 feet.  How can I demag a piece of steel that size?  Any ideas?
Reply:LOL, I wish I had a table that size ... magnetized or not.... I do not know how to fix the table..but I think there are some ' silly putties ' which can be used to clean your file...Or perhaps a file could be wrapped with a wire and electricity applied... and slowly withdrawn ?   Like tape recorder heads used to be demagnetized... ?Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:Durring the second world war Charles Goodeve designed a system  to "wipe" steel merchant ship hulls to reduce magnetisum to combat magnetic mines. I believe the process used high amp DC curent passing thru a copper wire that was dragged across the ships hull. It was a simple process for ships that didn't have their own degausing systems and didn't require a giant coil that the ships had to be passed thru like earlier methods..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Since we are constantly warned not to strike magnets with anything or they will lose their magnetism, why not strike the table sharply and see what happens?  Bitch-slap the "attractiveness" out of it?Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:Originally Posted by DougAustinTXSince we are constantly warned not to strike magnets with anything or they will lose their magnetism, why not strike the table sharply and see what happens?  Bitch-slap the "attractiveness" out of it?
Reply:Degause the table by wrapping a coil of stinger lead around it and then burning some high amperage rod with your AC welder output.The alternating magnetiig field in the coiled stinger lead will cause the magnetism in the steel of the table to neutralise.I offer three choices: Good, Fast, & Cheap. You may pick two.Hobart AC/DC StikMate LXHarbor Freight AD HoodHarbor Freight Industrial Chop SawDeVilbis 20 Gallon, 5 HP Compressor
Reply:Haul it outside and build a good fire under it, get it hot enough that some sheet metal attached to the underside will fall off...and then figure out how to keep it from being crooked when done? If you need to know how hot, look up Curie Point for steel.Actually, it might work if you can get a few hundred feet of heavy wire and evenly wrap the table with it, then hook the welder up to that wire and run AC through it, starting at minimum current, then quickly increasing to the maximum the wire or welder can stand and quickly reducing to minimum again. With AC, the magnetic field is also alternating polarity as the current does; with DC it's fixed so will tend to magnetize the table instead. With the changing polarity and decreasing field strength, the steel should approach zero magnetism at the end, assuming the field was strong enough at full current to do anything at all.  This assumes your welder can change current under load, of course.Obviously, safety is important. Insulation needs to be decent, the wire size needs to be adequate, the time short to keep heat build-up down. Might also help to be pounding on the table with a rotary hammer while doing this operation; helps the molecules re-orient themselves in the changing field.Might be able to test the strength of the table's field with a compass; see how far the needle is affected at some specific distance and angle from the table, then compare later from the same point. Or see how heavy a piece of sheet metal will stay attached; this would require similar (width and length) pieces of metal of different thicknesses. Probably not a simple mathematical relationship either.
Reply:Originally Posted by Oldiron2...Might be able to test the strength of the table's field with a compass....
Reply:I have the same problem on a couple of my tables.  They've spent their lives as welding tables for 25 years now.  I just live with it and clean all my tools with compressed air.Good Luck,HAWK
Reply:Try this.  You have nothing to loose.Attach ground clamp from AC welder to one end of the table.  Strike arc and weld a little at other end with same AC welder.Question - does the table lie in a "north / south" direction?Gordie -- "I believe you understand what you think I said, but I'm not sure you realize that what you heard is not what I meant."
Reply:Originally Posted by NiteskyTry this.  You have nothing to loose.Attach ground clamp from AC welder to one end of the table.  Strike arc and weld a little at other end with same AC welder.Question - does the table lie in a "north / south" direction?
Reply:So I gave it a try - burned up some 6013's I'd had lying around.  As far as I can tell, it may be a little better.  When I swept shavings off the edge before, some would stick to the edge rather than fall off.  Now they all fall off.  I had my file between the ground clamp and the table hoping it'd lose its magnetism, but it's as magnetic as ever.  Oh well.On a side note, I don't think I'd ever run 6013's on AC.  Not even sure if you're supposed to or not, since the box didn't say and I don't ever use them.  But the slag sure did peel up nicely for some old "Weld-It" brand rods kept in an unsealed container for 5 years.  The beads were similar to 7018 in appearance.
Reply:AC is the right way to go but it's not been described exactly right. You need to expose it to a AC field that slowly tapers off. I'm having trouble describing it with words this morning for some reason but as the field reverses the slow decay of the will cause it to be demagnetized. A degauss coil like on guy described for ships would be a AC magnet.   Ok. Let me describe the degaussing of a CRT in a TV maybe it'll come out understandable. All CRT's have a degauss coil on them but can still become magnetized (often because of a kid putting a magnet on them or even from sitting unused in the earths magnetic field). This will cause funky colors since it bends the electrons going to the screen (I'm not going into CRT theory this morning). Anyway the built in degauss coil is hooked to a thermister that slow decays the field when the set is turned on. A manual coil can be made with the coil from a old TV but it will have a limited duty cycle before it gets hot and melts. It's basically a large coil of wire that makes a electromagnetic field. You can twist the coil from a TV together like you would a bandsaw blade and tape it. Then plug it into power. By bringing the coil in close proximity with the screen and slowly moving it around and then slowly backing away you will have demagnetized the TV screen. A  switch in the power cord makes it nicer to use since you don't want to have it on for to long. I used one like this for a long time when I was doing TV repair. I finally managed to get ahold of a old commercially made one about the time I quit doing TV's.  Now on to your problem. Something similar would work the hard part is going to be getting a strong enough magnetic field to actually change the heavy metal table top without melting down the coil. The welding lead suggestion has some merit and if done properly I think you might manage to make it work.   I think I'd first try to make a coil with welding leads say about 2' in diameter. Put as many wraps as possible in it. Set the welder as high as you can safely run it in AC with the leads connected together. Slowly drag the coil across the table top. Now this is important instead of simply turning off the welder at the end of the table you either have to slowly back the coil away from the welder or you have to slowly turn down the welder.  There are a few other methods I can think of but this seems to be the easiest I can think of at the moment.Millermatic 252XMT 304'sDynasty 280DXHypertherm PowerMax 1250Miller Trailblazer 302 EFIOptima PulserXR feeder and XR Edge gun and more athttp://members.dslextreme.com/users/waynecook/index.htm
Reply:Originally Posted by irish fixitAC is the right way to go but it's not been described exactly right. You need to expose it to a AC field that slowly tapers off. I'm having trouble describing it with words this morning for some reason but as the field reverses the slow decay of the will cause it to be demagnetized. A degauss coil like on guy described for ships would be a AC magnet...... Something similar would work the hard part is going to be getting a strong enough magnetic field to actually change the heavy metal table top without melting down the coil. The welding lead suggestion has some merit and if done properly I think you might manage to make it work.   I think I'd first try to make a coil with welding leads say about 2' in diameter. Put as many wraps as possible in it. Set the welder as high as you can safely run it in AC with the leads connected together. Slowly drag the coil across the table top. Now this is important instead of simply turning off the welder at the end of the table you either have to slowly back the coil away from the welder or you have to slowly turn down the welder.
Reply:Originally Posted by Oldiron2I described how the current should quickly be turned up, then down...and why. Remember that here time is based on cycle period of AC; 60 hz.The reason for the great length of wire is to have many turns, each increasing the field strength. Should be ~a linear relationship. Might have to do sections of the table successively if the field strength is too low with the entire table wrapped as first suggested.Going directly through the table only provides one path or  half 'loop'; using the wire provides many more. Only benefit is greater amperage possible, but number of loops will be more important than maximum amps, IMHO.If this is done right, there wouldn't be time to drag the coils. Even a #14 wire can carry a huge current for a few seconds without failing; over a long time (maybe 30 seconds?) it might burn up.
Reply:My thinking is that you have to be more thoughtfull about applying the solution before you know the details of the problem. Those details being the polarity that you are attempting to change.  Being magnetized is the nature of iron. There will always be magentic pockets within larger pieces and at the same time  there will always be external influences applied to that singular piece. However a piece like a table is generally only considered magnetized when all or most of the pockets become oriented in the same direction, polarized, positive-negative. Now to apply a tempory DC cure (+ & -) without first determining the existing bias of the item we are trying to cure could actually have a reinforcing effect. It woud be a blind dart throw. You have a 50/50 chance of getting it right based just on the bias alone. Add to that too long or too strong and you could easily reverse the the bias/polarity in the event that you did not reinforce the existing polarity, no net gain. Seems like something more radical would stand a better change of disrupting the bias. Probably an AC application or a rapidly reversing DC or random paths over small areas-----------------.  Speaking of random, these are just random thoughts. "The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:Originally Posted by SandyMy thinking is that you have to be more thoughtfull about applying the solution before you know the details of the problem. Those details being the polarity that you are attempting to change.  Being magnetized is the nature of iron. There will always be magentic pockets within larger pieces and at the same time  there will always be external influences applied to that singular piece. However a piece like a table is generally only considered magnetized when all or most of the pockets become oriented in the same direction, polarized, positive-negative. Now to apply a tempory DC cure (+ & -) without first determining the existing bias of the item we are trying to cure could actually have a reinforcing effect. It woud be a blind dart throw. You have a 50/50 chance of getting it right based just on the bias alone. Add to that too long or too strong and you could easily reverse the the bias/polarity in the event that you did not reinforce the existing polarity, no net gain. Seems like something more radical would stand a better change of disrupting the bias. Probably an AC application or a rapidly reversing DC or random paths over small areas-----------------.  Speaking of random, these are just random thoughts.
Reply:Originally Posted by tbone550Answer - Yes, it's north / south.  I'll have to give that AC idea a try.  As a matter of fact, I think I'll go try it now.  You'll have to wait while I hook up the Dialarc.
Reply:Originally Posted by NiteskyTake a steel bar, point it towards magnetic north and lower the north end slightly, tap it a couple of times with a hammer and it will turn magnetic.  An old science trick.
Reply:Much easier to de mag your tools as the table problem will return and drive you nuts.V.
Reply:Slick homemade demagger. Heed safety advice later in thread when building:http://mb.nawcc.org/showthread.php?t=12699