De-magnetising

[Garry ColesParticipant @garrycoles69390]

[Garry ColesParticipant @garrycoles69390]

Hi. I've got a lot of tools, like spanners & tooling bits etc that are picking up swarf all the time. Very annoying having to wipe them down all the time. Is there a way to de-magnetise them or do I have to put up with it.

Is there anybody that can give me some advice please.

Thanks

Garry

[Brian HParticipant @brianh50089]

The Eclipse demagnetisers are excellent although a little pricy. I recently bought a Chinese one for small spanners and screwdrivers and was surprised that it even worked on a 1/2" Whit spanner, although it took several passes to completely demagnetise.

Brian

[Garry ColesParticipant @garrycoles69390]

Thanks Brian. Have looked at some online and yes they are quite pricey.

[larry phelan 1Participant @larryphelan1]

Bought one of those things recently in Lidi, quite cheap and totally useless.

[Tony Pratt 1Participant @tonypratt1]

Posted by larry phelan 1 on 24/10/2020 09:47:41:

Bought one of those things recently in Lidi, quite cheap and totally useless.

Returned for a full refund?

[David George 1Participant @davidgeorge1]

I take anything to local toolmaker and borrow his Eclipse demag it only takes a few minutes.

David

[John PParticipant @johnp77052]

I made this unit from the drawings in Model engineer
designed by H.D. Bickley
Vol 167 no 3903 16 August-5 September 1991.
It works very well for small workshop items.

John

[Peter G. ShawParticipant @peterg-shaw75338]

Many years ago, in what seems like a different life, I bought a tape head demagnetiser. You can tell how old – it has a 5A round pin rubber plug on it. Sorry, got sidetracked. Anyway, it still works and I use it reasonably successfully for demagnetising stuff. Whether or not it will handle spanners I don't know. As someone else has said, it can be necessary to have two or more attempts, and for what it's worth, I always remove the tool slowly by at least 600 mm thus gradually reducing the demagnetising field before switching it off.

Peter G. Shaw

[Martin CargillParticipant @martincargill50290]

On the same subject. My bench vice at work has become magnetised, Its a full sized 6" vice, any ideas how to demagnetise it?

Martin

[Jim NicParticipant @jimnic]

I also use a small cheapo Chinese demagnetiser from the bay. My experience of it is similar to Brian H in that it can take a couple of goes through the procedure to completely get rid of residual magnetism but the end result is usually good. I've not tried it on anything bigger than a 12mm spanner.

Jim

[John BaronParticipant @johnbaron31275]

Hi Guys,

An easy way to get a demagnetiser, is to take the rotor out of an old washing machine pump motor and throw it away. Passing your magnetised tool through the stator aperture will quickly demag it !

NOTE: The coil will very quickly get hot and overheat so you only get about 30 seconds to demag stuff. You can use the open end of the metal stator to demag larger items.

 

 

Edited By John Baron on 24/10/2020 16:37:54

[Ian HewsonParticipant @ianhewson99641]

For non too delicate tools, screwdrivers spanner’s etc, a sharp rap on the vice will often demagnetise them.

[SteviegtrParticipant @steviegtr]

That's all i do , a quick tap on a hard surface usually does the job.

Steve.

[John PurdyParticipant @johnpurdy78347]

I made this one from the same ME article as John.  I used a power transformer that came from a Peavey guitar amp that had come in for repair. I had replaced it as the thermal fuse in the primary had opened. It had sat around on the floor of the shop  for a number of years as I couldn't make myself throw it out.  I wired the two secondary windings in series (80 and 30 volts) to the power cord (120 volt supply).  Note the two wood strips where I milled slots in the laminations to break the flux lines in the core, milled down til there was about 1/16" of the laminations left. Works great, de-magnetizes even the largest wrenches in a few seconds, also quite successfully  de-magnetized the 4" 3 jaw lathe chuck. The thin Bakelite sheet glued to the top stops the items to be de-magnetized from sticking to the laminations.

John

Edited By John Purdy on 24/10/2020 18:37:07

Edited By John Purdy on 24/10/2020 18:53:01

[not done it yetParticipant @notdoneityet]

I have an Eclipse demagnetiser. Not sure exactly how good it is – it seems like one is needed if one surface grinds using a magnetic chuck? I also have a couple of largish torroidal transformers which I expect would work quite well for passing items through the centre.

[Simon Williams 3Participant @simonwilliams3]

Somebody correct me if I'm wrong, but isn't the magnetic field in the centre of a toroid identically zero? The lines of flux are toroidal to connect the windings magnetically, it's only leakage flux remnant at the centre?

Rgds to all Simon

[Robert Atkinson 2Participant @robertatkinson2]

Posted by Simon Williams 3 on 24/10/2020 19:27:51:

Somebody correct me if I'm wrong, but isn't the magnetic field in the centre of a toroid identically zero? The lines of flux are toroidal to connect the windings magnetically, it's only leakage flux remnant at the centre?

Rgds to all Simon

Correct

A Toroid is useless for this application.

Robert G8RPI

[SamsarandaParticipant @samsaranda]

About 30 years ago when working in the inspection department of a manufacturer that produced equipment using magnetic drives we had a large coil demagnetiser for demagnetising certain components, I was using a bowers tri point micrometer and it was so magnetic that it had a nest of swarf clinging to it so I thought I would use the demagnetiser, that’s was ok but I forgot that with so much current flowing in the demagnetisers coils the bowers mic heated up very rapidly, so rapidly that it got so hot I nearly dropped it. I learnt from this experience how quickly a coil can generate heat, the mic was certainly demagnetised though.
Dave W

[Peter G. ShawParticipant @peterg-shaw75338]

Just a thought. perhaps someone can advise.

I have a cheapo XP arc welder. Now I haven't opened it up, but I believe it consists of a large & heavy transformer. I wonder if this could be modified into a dual purpose device?

Peter G. Shaw

[Robert Atkinson 2Participant @robertatkinson2]

If the welder has an AC output then yes, you could use it as a power source for a demagnetiser. A DC output will make a magnetiser Wind a coil out of heavy gauge insulated wire (4mm2 would be a good start, it has to carry the current for several seconds) with as many turns as you can and the hole in the middle big enough to get the item you want to demagetize into.
Start with the welder on it's lowest AC setting.
Put the item you want to demagetise into the center of the coil (if it's longer than the coil leve the excess sticking out the far side), turn on the current and slowly (over several seconds) pull the item straight out of the coil and about a foot away in a straight line, then turn off the current.

EDIT:

As a guide a inverter welder or one with electronic controls is likely to be DC, a cheap one with a big knob or switches to set current will be AC.

Robert G8RPI

Edited By Robert Atkinson 2 on 24/10/2020 22:07:21

[Peter G. ShawParticipant @peterg-shaw75338]

Robert,

The XP welder has no controls whatsover. One simply prepares everything first, then switches on at the socket and with helmet on, poke the rod in the general direction of the parts to be welded and hope it works. Crude? Most definitely. AC? I assume so.

Anyway, thanks for the comment, I'd been wondering how to coil up the welding leads – the idea of using a 4mm2 wire to form a coil is a lot better. It would, I think, be possible to create a coil, then clip on the earth and power leads to the coil, switch on the power and hopefully away we go. Room here for experimentation I think. And before anyone says anything, yes, there are safety consideration, eg the coil would have to be attached to a board which in turn would be clamped down somehow. Heating? Short-circuiting? Well the unit does have an internal cutout for if one does too much welding. And the process of welding with this thing is nothing more than using a short-circuit to create the welding heat.

Thinking about the tape head de-magnetiser I mentioned earlier, I can feel the effect of the magnetic pulses as I draw the tool away from whatever is being demagnetised. Which makes me wonder about the strength of any pulses from this beastie.

Cheers, and thanks,

Peter G. Shaw

[Howard LewisParticipant @howardlewis46836]

The AC current in the coil will produce an alternating field, a the flux varying between North maximum and South maximum, following the sine curve of the voltage (and the current )

As the object is withdrawn, the field in the item diminishes according the inverse square law, until it is effectively zero.

In this way the magnetism in the object is varying and reducing until eventually it becomes Zero.

I am sure that Robert will, quite properly, correct me if any of this wrong.

Howard

Edited By Howard Lewis on 25/10/2020 12:43:20

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