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Garry Coles24/10/2020 08:05:51
83 forum posts
95 photos

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.



Brian H24/10/2020 08:11:16
1961 forum posts
108 photos

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.


Garry Coles24/10/2020 08:48:18
83 forum posts
95 photos

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

larry phelan 124/10/2020 09:47:41
903 forum posts
17 photos

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

Tony Pratt 124/10/2020 09:50:48
1342 forum posts
5 photos
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.crying

Returned for a full refund?

David George 124/10/2020 10:04:03
1428 forum posts
456 photos

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


John Pace24/10/2020 10:05:11
217 forum posts
198 photos

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.



Peter G. Shaw24/10/2020 10:44:17
1232 forum posts
44 photos

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 Cargill24/10/2020 10:51:51
150 forum posts

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


Jim Nic24/10/2020 12:53:09
288 forum posts
164 photos

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.


John Baron24/10/2020 16:37:01
359 forum posts
147 photos

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 Hewson24/10/2020 16:53:52
281 forum posts
25 photos

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

Steviegtr24/10/2020 17:50:30
1776 forum posts
235 photos

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


John Purdy24/10/2020 18:34:51
237 forum posts
131 photos

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.


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 yet24/10/2020 19:21:07
5378 forum posts
20 photos

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 324/10/2020 19:27:51
561 forum posts
80 photos

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 224/10/2020 19:45:50
883 forum posts
17 photos
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


A Toroid is useless for this application.

Robert G8RPI

Samsaranda24/10/2020 21:16:39
1018 forum posts
5 photos

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. Shaw24/10/2020 21:35:32
1232 forum posts
44 photos

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 224/10/2020 21:53:31
883 forum posts
17 photos

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.


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

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