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Electro Magnet/Demagnetizing

standish

Cast Iron
Joined
Nov 12, 2003
Location
Boise, ID, USA
Way back in grade school the teacher did a "science experiment" wherein she wrapped a toilet paper tube with copper wire and connected the wires to a 6V dry cell via a knife switch. Then she proceeded to demonstrate that a screwdriver could be inserted in the coil and the switch thrown to activate the current, and the screwdriver would be magnetized. Then she showed us that doing the same thing again would demagnetize the screwdriver. Seemed pretty simple at the time.

Does anyone here know if something like this can be done on a grander scale to demagnetize things around the shop? Like maybe use a battery charger as a source of current. Maybe a source of how-to instructions?
 
Yes, it will work.
I used to work in a speaker factory, on the woofer line, and we would get our magnets from the magnet factory non magnetized. These were donut shaped ceramic magnets, and we would glue them up to steel backplates, and build up the entire speaker before we magnetized em. That way the gap was blown out and sealed up before it was magnetized- much less chance of stray metal chips getting stuck in there and irritating customers.
One of the engineers there built a homemade magnetizer- I dont recall the power supply very clearly- But it was pretty beefy. The coil itself was made out of big rectangular wire we used to wind chokes for the crossovers- maybe 1/8" x 3/8" wire, predipped in clear insulating coating. Anyway, we would put the completed speaker in the coil, hit the power, and they would get magnetized.
MSC sells little tabletop versions for screwdriver sized objects -70 bucks.
They even sell a cordless model.
www.mscdirect.com/IWCatProductPage.process?Merchant_Id=1&Section_Id=2010011&pcount=15&Product_Id=174431&Keyword=Y
 
You want to de-guass things. This is
done by applying a large alternating
field to the item, and then slowly
and smoothly reducing the amplitude
over a fairly long time.

There are two easy ways to do this, one
is to purchase a tape head degausser
from a place like radio shack. The other
el-cheapo way for small stuff like screw
drivers and so on is to use a Weller
soldering gun.

Open up the tip so you can pass the item
through it, and then turn the gun on and
pass the article throught the wire tip
back and forth a few times. Then, without
letting up on the trigger, slowly bring the
gun and the piece apart, to arm's length,
and then shut off the gun.

Jim
 
For your interest, demagnetisers are commonly used wherever surface grinders are found - for example, if you sharpen press tooling, you usually need to then demagnatise to prevent any slugs etc hanging around the tooling. (This is because the magnetic chucks used on the grinders will magnetise the workpiece)

The type I have used are the Eclipse table top version, you just push the button and slide the workpiece over the top surface of the demagnetiser a few times.

http://www.eclipse-magnetics.co.uk/MechanicalMagneticChucks/1528.htm
 








 
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