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Alert ! Magnetized Bergeon N˚4040 movement holder.

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Dear all;

Working on a chronograph, after assembling the demagnetized motion-parts, the motion work ran all over the place. Next to a few other suspicions, the possibility that something had gone wrong during the demagnetization of the parts was one of them. Started checking the movement with a compass, but actually found that my metal Bergeon N˚4040 movement holder was magnetized.

Even though the holders' side-plates and guides are made out Stainless Steel, the adjustment screw and circlip aren't. To find out exactly what was magnetized, I disassembled the holder and put each part on the compass.

First picture the compass in "neutral";


Checking the both side-plates, the small part at first;


Some slight residual magnetism in the side-plate with the guide-rails;


However, very strong residual magnetism in the screw and circlip. So much so that I could move the compass needle in any desired direction;




To be honest, I never checked & suspected my movement holder for magnetism. When demagnetizing watch-parts, I always do keep all other metal objects well away from the demagnetizer.

I have used the movement holder already for quite some years, so how and when it became magnetized is unknown to me. That it can become (strongly) magnetized is a new lesson to me.

Be aware ?



Edited by Endeavor
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One thing I was taught at the beginning of my watchmaking apprenticeship always demagnetize all of your tools before you start a new watch repair and always  demagnetize the watch you are about to repair.


You don't expect that from Bergeon as you know their tools are expensive, that is a bad design. Contact them you never know they might send you something. 


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45 minutes ago, Endeavor said:

Even though the holders' side-plates and guides are made out Stainless Steel

Thee plates of the 4040 don't look as made of SS and Bergeon doesn't say that they are, what they say is "nickeled sheet metal".  https://www.bergeon.swiss/porte-piece-reversible-1107.html

The 4040P holder has plastic plates, hardware could be SS, hence fully amagnetic.

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Posted (edited)

The 4040 plates did appear as being SS.

I'm aware of the 4040P with carbon-fiber plates, but if the adjustment screw and guide-rails are not SS, you may have the same problem (?)

The main residual magnetism seem to sit in the adjustment screw and circlip. Whether this could have been caused by years of rotation (clock- anti-clockwise) in perhaps two different composition materials is for me a guess.

But the fact is, it's there and lurking right underneath the movement at hand.

Edited by Endeavor
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