# How to properly use a demagnetizer?



## JustBlueFish (Oct 2, 2016)

I picked up a compass the other day and I noticed on several of my watches that when I move then around the compass I get a very minor response. The needle doesn't go flying around like crazy, like you would see if you place a magnet near the compass, I just get a very small flutter of the needle as I pass my watches over/around the compass. So, I figured I'd pick up a $12 demagnetizer off of Amazon.

I got the demagnetizer today and I don't really know how to properly use it. I didn't toss a watch on it, I tried with something else, as my first test of the tool. My results were less than impressive.

I have a screw driver with removable bits. I took a very magnetized screwdriver bit, which when tested on the compass gives a very dramatic response to the compass needle, as the item I'd first try to demagnetize. The demagnetizer didn't come with any instructions, but based on what I've been able to Google you should set your item on it, hold down the button, and slowly lift your item away while it's running for 6 or so seconds.

I did that procedure, several times, but the screwdriver bit is still magnetized a little. It doesn't affect the compass like it did prior to me running it over the demagnetizer, but it still does make the needle twerk a little bit. It's actually now giving roughly the same sort of response I get when I run my watches past the compass.

So, why am I unable to completely demagnetize my screwdriver bit? Am I doing something incorrect? I am reluctant to toss a $400 watch on this thing if I can't even manage to properly demagnetize a .50 cent screwdriver bit.

Thanks for the help.


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## J.D.B. (Oct 12, 2009)

I have that one, too. It came with directions, though. Place the watch, face up on the blue box and push and hold the red button. Count to maybe four or five (seconds) and then start lifting the watch up to a few feet above the blue box over the next four or five seconds before letting go of the red button. Basically a ten-second procedure.


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## Camguy (Nov 23, 2012)

Is it best to have the movement out of the case? My Seiko srpa21, for example, is magnetic resistant to 4,800 A/m, and it seems as if that would defeat the effect of the demagnetizer.


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## JustBlueFish (Oct 2, 2016)

J.D.B. said:


> I have that one, too. It came with directions, though. Place the watch, face up on the blue box and push and hold the red button. Count to maybe four or five (seconds) and then start lifting the watch up to a few feet above the blue box over the next four or five seconds before letting go of the red button. Basically a ten-second procedure.


Thanks for the info.

I tried following that instruction, testing it on my magnetized screw driver bit, and I'm still getting a slight response when moving the bit near a compass. Any idea why it's not completely demagnetized?

Sent from my iPad using Tapatalk


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## BenchGuy (Sep 23, 2012)

Compass...this device may give you a qualitative indication of whether an object produces a magnetic field, but it is not the definitive tool. The needle is magnetized and has its own N-S polarity. It will be attracted to ferrous metal...even if the metal is not polarized. So a needle swing may be an indication that the item you're "testing" is polarized and producing a magnetic field...or just that is it ferrous metal.

Effectiveness of demagnetizers depends somewhat on strength of the field you are trying to disrupt...and strength of the demagnetizer. The little blue Chinese units are weak. Good luck trying to demag a pair of pliers with them. And a lot of folks report difficulty using them with watch movements/parts. Tunnel demagnetizers produce the strongest field.

What you are doing when you turn the unit on, is creating a magnetic field. If you leave the piece stationary on the unit, you'll magnetize it. When you lift the piece straight up, you are passing it through an area of the field which is changing orientation and weakening with distance...with the intention of mixing up the "domains" in the subject piece...resulting in the deGaussed condition.

Instantaneous demagnetizers do the "lifting" for you...in that they produce an alternating N-S field which decreases in strength, then completely dissipates. Place the object on the circle, press the button. Click. Your done. A more densely ferrous piece might require 3 or 4 clicks. 

Unless you find a used MagnaFlux or Elimag on the internet, the new ones are pricey. They are limited in "strength"...and may not do your pliers, either. But wok fine for screwdrivers and tweezers (although I prefer anti-magnetic tweezers, to begin with).

Tunnel demagnetizers are the strongest...but again, require drawing the object through the tunnel to work. If you put the object in a small plastic box, this can facilitate handling. Drawing the object through along a reasonably centered line, works best.

I prefer the instantaneous type. Effectiveness with watch movements is seen in the timegrapher results. Effectiveness with tools can be determined with a small screw...if the tool will not attract a hairspring stud screw, you've done good (note: screw must not be magnetized, either).

Regards, 
BG


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## Molliedooker (Jul 23, 2014)

Everything BenchGuy said above especially this.
"What you are doing when you turn the unit on, is creating a magnetic field. If you leave the piece stationary on the unit, you'll magnetize it. When you lift the piece straight up, you are passing it through an area of the field which is changing orientation and weakening with distance...with the intention of mixing up the "domains" in the subject piece...resulting in the deGaussed condition."

I use the cheapy. I only hover the item just above the machine and slowly lift it straight up. I do this app. three times.


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## J.D.B. (Oct 12, 2009)

Camguy said:


> Is it best to have the movement out of the case? My Seiko srpa21, for example, is magnetic resistant to 4,800 A/m, and it seems as if that would defeat the effect of the demagnetizer.


I don't remove the movement, no. I just push the button and start counting then lifting the watch away. I've used it for two, so far and it worked well. Some one else mentioned doing it more than once and yeah, on the second watch I de-magged I did it three times.


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