On 23 Mar 2006 20:21:32 GMT, Dave Hinz
wrote:

On Thu, 23 Mar 2006 13:33:13 -0600, Jon Elson wrote:

Dave Hinz wrote:

So how do I demag this sucker?

How big is the part?

Roughly 8" x 1.056" x 1.200" before I started removing chunks, curls,
& chips...

For very small parts, I use a Weller soldering
gun, the
kind with the two posts sticking out the front, and the copper "wishbone".
If necessary, I can make a ring of #12 wire that has a bigger opening than
the standard element.

Doesn't apply in this case, but thanks, I do have that type of Weller
iron (along with 3 other Weller irons - all surplus but good stuff)

For larger pieces, do you have an AC TIG welder? If not, then try an AC
buzz-box.

I've got a neighbor who is a blacksmit, I bet he can help me out on this
one. Thanks.

What you are doing here is passing an AC electromagnet over the part,
and gradually drawing it away. The 60 times per second alternating
field of decreasing intensity gradually reduces the remanent field to
zero. (When I say gradually, it only takes a couple of seconds.)

Right, so I'm inducing a bias frequency as a B1 to change the B0. Funny
how I tend to forget that all that schooling translates into real world,
sometimes. I guess it's because so many times it doesn't.



Every colour TV is fitted with a demagnetising coil
which is designed to do just that when connected to normal
50/60Hz power.

Raid a junk TV for this coil which is wrapped round the
large flare of the display tube. As removed it is a large
diameter coil. Twist the coil so that it is re-arranged into a
three turn loop (this is the same trick as twisting a vee belt
into a three turn loop to make it smaller for storage).

You now have a very convenient demagnetiser - pass the
workpiece slowly (a second or so) through the coil and it will do
a thorough demagnetising job. The coil is short time rated so
don't leave it on too long - 10 to 20 sec is OK.

Jim


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