Eclipse.

Brian

Depending upon the size, all that you need to demagnetise an item is to pass it through a fluctuating magnetc field.

Cassette recorder heads are demagnetised using a "wand" fed with low voltage AC.

Larger items are demagnetised by passing through a coil carrying an AC voltage.

So, it should be possible to make a demagnetiser, AS LONG AS YOU KNOW WHAT YOU ARE DOING.

I E Electrically safe,

No acessible terminals; earthed, or double insulated, and not taking excessive current likely to cause overheating and fire. The insulation should be adequate for the voltage applied. (Don't put 230Volts AC onto something insulated for 12 volts!)

For short term, intermittent use, an Induction motor, minus the rotor, used WITH CARE, might suffice, to pass small items through.

But switch off, and disconnect when not in use.

Now this should bring in folk who really are expert in electrics and such devices

Howard

Here is a home made unit for small tools that doesn’t use any power .

**LINK**

i use a degaussing wand that is designed for degaussing tv screens , bought it of ebay and is ok foe small tools like digital callipers.

I've degaussed a TV by furiously waving a loudspeaker manget at it and slowly retreating. Took a couple ot tries to get it spot on.

Neil

How about a Greiner Magnomatic Demagnetiser? Meant for watch and clock parts but also suitable for small tools.

Interesting that demagnetisers range in cost from waving an old loudspeaker magnet at the object for free up to professional devices like the Greiner costing a cool £1200.

Unless money is unlimited it pays to think about what the tool is to be used for and how often. My casual need to demagnetising the occasional screwdriver is easily met by carefully passing the object over a magnet in different directions until I manage to reduce the residual magnetism 'enough' by trial and error. An amateur clockmaker / watch-repairer would probably need a less labour intensive demagnetiser often enough to buy at least a simple AC demagnetiser. These still require the operator to manipulate items, but are easier to operate and get rid of most residual magnetism. Prices start from about £30.

Looking at the expensive Greiner, you get a far more sophisticated unit for your money. Its operation appears to be completely deskilled. The item to be demagnetised is dropped in the slot and the button pressed. I suspect an AC magnetic field is scanned several times from side to side along the item. When the first pass has finished, the operator presses the button again causing a second scan at 90° to the first. Expensive but no doubt results are quick and effective. The Greiner is ideal for a profitable repairer working against the clock. It's completely over the top for me and my screwdrivers unless I find one dirt cheap at a car-boot sale!

Doesn't help much, but as most of the cheaper units consist of little more than an AC coil and a timer, almost any of them will do for most purposes. For more serious use, what's your budget Chris?

Dave

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

They used to sell demagnitisers for VCR cassettes. There ought to be a few of those going spare still.