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Screwdriver Magnetiser/Demagnetiser

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Neil Wyatt31/10/2014 21:16:03
18990 forum posts
734 photos
80 articles

I've just got one of these simple things with two holes. It works 100%, magnetising and demagnetising a screwdriver every time.

Inside, two magnets. easy to see how two magnets that reinforce each other magnetise the screwdriver, but how does the demagnetiser hole work?

I have a large pile of iron filings nearby, which shows the magnets are aligned, so the magnetised hole puts the screwdriver through two strong fields. Demag makes it run along the field. Demag also works best if you use it quickly.


Danny M2Z01/11/2014 06:03:12
962 forum posts
1 photos

G'day Neil.

Maybe opposing magnets in the de-magnetiser hole cancel any residual magnetism in the screwdriver?

I actually use a cassette head de-magnetiser, left over from my early computing days (when all home brewed software came on cassette tapes). It looks a bit like an 'adult toy' but it sure is effective. Works on the principle of an alternating field (current) reducing in intensity as one slowly moves it away from the tape heads.

I mention this because I just 'resurrected' my first computer, a Z-80 based Aussie 'Microbee' that was hand soldered together in 1983...even the CRT green screen still works! Some of the old cassette tapes were dodgy but the de-magnetiser soon fixed the data recorder. Now back to re-learning Z-80 assembly language and teaching the old girl to talk to an Arduino via a serial shield (horrible name btw, why just not call it an I/O interface) in progress.

I am not ashamed to be called a 'Hacker' btw, because way back 'then' it earned a lot more respect than the term does nowadays.

I hope you do not mind me bending your thread a little Neil

Regards from Oz

* Danny M *

Edited By Danny M2Z on 01/11/2014 06:05:11

Neil Wyatt01/11/2014 09:09:51
18990 forum posts
734 photos
80 articles

No, the demag side just passes it across the side of one magnet.


Russell Eberhardt01/11/2014 10:00:39
2728 forum posts
86 photos

This is what I use:

It works fine and is big enough to demagnetise my chuck jaws. I got fed up with swarf sticking to the work!


Andrew Johnston01/11/2014 10:40:13
6574 forum posts
701 photos

It will be interesting to hear how the darn thing works! I was under the impression that demagnatisers used an AC field which was gradually decreased to zero, or the item moved slowly away. I don't see how it works with just a magnet. Somebody must know, and will spill the beans!


Michael Gilligan01/11/2014 10:56:25
20052 forum posts
1040 photos
Posted by Andrew Johnston on 01/11/2014 10:40:13:

I don't see how it works with just a magnet. Somebody must know, and will spill the beans!



There was some interesting discussion on a previous thread.


jason udall01/11/2014 17:24:20
2031 forum posts
41 photos
Having remembered and now reread that previous discussion. ..

Let us suppose that a tool is held in one hand and magdemag gizmo in other. ..
A few strokes of the tool through the magnetise hole.makes ( say) the tool tip north.
Now you want a tool demagnetised. ..again A stroke in the demag hole...
Oh bum..not demaged...
Try this..First magnetise then demag with one or more strokes in demag slot..

Why this might work.
The orientation of the poles in mag hole combined with how its held ..leaves a permanent "set" one way or the other.. ( hold tool and gizmo differently and you might get south at tool tip) we have a known state in the without changing grip , take a stroke in the demag slot..which attempt to magnetise the other result nil
If you went at the tool with an unluckily alligned might just magnetise it some more.....
You could use what UTM..or UTH.. did when they needed non magnetic tools.....bronze..screwdrivers..spanners..socket sets....even wire snips

Edited By jason udall on 01/11/2014 17:28:26

AJS01/11/2014 22:41:20
37 forum posts

My demagnetiser is the stator from a domestic washing machine pump. The impeller had failed and the pump was replaced.

In use the coil is energised by the mains supply with the item to be demagnetised held in the magnetic field; the item is then slowly withdrawn from the field before the electricity supply is switched off.

Of course precautions must be taken to prevent contact with the live coil windings whilst carrying out this operation. Enclosing the stator in a nonconductive box with a hole to allow the item to be operated on would seem sensible.


Ian S C02/11/2014 09:52:47
7468 forum posts
230 photos

Here's my demagnetiser. Ian S Cdsc00682 (640x480).jpg

Oompa Lumpa02/11/2014 09:58:44
888 forum posts
36 photos

How many channels does that radio get Ian?



The Merry Miller02/11/2014 13:11:15
484 forum posts
97 photos

You may be interested to know that CPC (Farnell) sell small a small version suitable for screwdrivers etc for,

wait for it, wait for it, 98 pence, yes 98 pence.

Now the sting in the tail is that V.A.T. will be added at 20%, oooh! I hear you say.

The CPC code number is TL1406805, don't all rush!

Len. P.

Robert Dodds02/11/2014 15:02:11
317 forum posts
59 photos


Not as cheap as Len P's but at 4.37 ex Toolstation the Wera magnetiser/demagnetiser does the job for me on screwdrivers etc
I have an old transformer that I modified some years ago that demags bigger stuff Needless to say I can't find the detail of the mod but feel it must have been in an old ME. I remember cutting a slot through some or all of the laminations and then back filled with araldite. Ring any bells with any one? (Preferably not alarm bells since its lasted for at least 20 years)

Bob D

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