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Magnetised tools

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Clive Hartland25/04/2011 18:59:59
2820 forum posts
40 photos
Suddenly I have a lot of tools both on the bench and on the lathe becoming magnetised!
Toolbits laid in the tray come up with a load of whiskers, any ideas?
Screwdrivers on the bench the same, laid down and then picked up and again whiskers on the edge.
I have no magnetic chucks, no magnetic stands or clamps. All very strange.
If I give the tool a knock it clears itself.
wheeltapper25/04/2011 20:01:35
424 forum posts
98 photos
you can make one from the primary winding of a transformer from a microwave oven.

it's a bit hard to get at but it works well.

Edited By wheeltapper on 25/04/2011 20:02:08

Ian P25/04/2011 21:44:17
2590 forum posts
114 photos
Although it is not my own idea I recommend making a demagnetiser out of an old central heating water pump.
The most suitable type of pump has a thin stainless steel plate between the two halves of its construction. One part (the wet side) contains the inlet and outlet ports, and the impellor, whilst and the other half has the electrical bits. The impellor is driven by the magnetic field being transmitted through the SS shim.
Throw the wet half away, fix the SS plate securely to form the working surface, ft a suitable switch and cable (Dont forget the earth lead!) and you have a useful tool.
I discovered thet its best not to leave it on for too long as without 'seeing' the rotor the windingtend to get hot after 15 minutes.
dcosta25/04/2011 23:22:55
496 forum posts
207 photos

Hello Clive!

In case You do not have access to some disposable equipment to make an demagnetizer from it (this happened to me...), you can purchase a small but eficcient demagnetizer. I bought one and am very pleased.
See, if you please, the following URL http://www.model-

Best regards
Dias Costa

joegib26/04/2011 07:53:30
154 forum posts
18 photos
If you only need to demagnetise small tools like screwdrivers and lathe tools, suitable demagnetisers can be had for a few pounds. This list from the Farnell site gives an idea of the range available:
In fact the first one I got was from Maplins bought ironically enough to magnetise some screwdrivers I use for electrical assembly. It can be useful to hang a screw on a magnetised screwdriver when inserting it in the innards of a computer case! But they work just as well to demagnetise small tools.
Ian S C26/04/2011 12:30:33
7468 forum posts
230 photos
I use Wheeltapper's system with the coil removed from a microwave oven transformer, I'v built a box around the coil, leaving a hole throgh the center. I run it of a transformer at a bit over 12V, it works well, and cost nothing, just a bitr of time. For bigger stuff I'v got a large round coil, the section through the windings is about 3" x 3", the hle through the coil is 10", the wire is 14 swg, and I use my workshop low voltage circuit at 17V. I have 2 of these coils, but one of them is in poor condition. Ian S C
Clive Hartland26/04/2011 19:39:08
2820 forum posts
40 photos
Thank you for all the comments about the magnetised tools, I am going to persaude my work partner to buy one of the de-guassing boxes from Farnell or Maplins.
John Olsen27/04/2011 07:19:34
1250 forum posts
94 photos
1 articles
I don't know if this is a true observation or just a misimpression that I have got, but it seems to me that when cutting tools start to get magnetised, it is often an indication that they may no longer be as sharp as they should be. That is not to say that they cannot get magnetised while still sharp...but I wonder if there is some tendency for them to magnetise when they are blunt?
Clive Hartland27/04/2011 09:29:37
2820 forum posts
40 photos
I am not too sure that blunt tools are the cause of this residual magnetism. It is a once or twice a year phenomina and it just puzzled me where it comes from, perhaps I live on a leyline?
A quick knock on something solid like the vice gets rid of it, its the source of it that i want to find, as I posted before i do not use magnetic mounts or tooling.
I would be more inclined to think it is coming in on the bar metal I turn, perhaps they use a magnetic crane device to move the metal and it is retaining the magnetism from the tool supplier?
Nicholas Farr27/04/2011 09:38:26
3360 forum posts
1542 photos
Hi, I think most tools that have any hardness to them will acquire magnetism from the Earths natural magnetic force, especially if they stay in one place for any length of time. Screwdrivers always seem to be prone to it. Don't know if it makes a difference if they happen to be stored in a north/south alignment.
Regards Nick.

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