How in the world? (Swiss hairspring removal)

jplotkin

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May 8, 2016
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How in the world do I remove the hairspring and balance wheel from this swiss balance cock?

I'd like to clean remove the balance wheel entirely so that I can clean the top jewels and re-oil. But there is no screw or hairspring stud that holds the hairspring into the cock. So how do I remove?

The cock assembly has a nice regulator pin that can conveniently be opened by screwing -- but apparently no convenient way to remove the balance wheel with hairspring:???:

Photos of the mystery attached.

balance-top.jpeg

balance hairspring.jpeg

balance-bottom.jpeg
on-tack.jpeg

movement top.jpeg
 

svenedin

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Jan 28, 2010
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You have to unpin the balance spring from the balance cock. I personally find that a difficult task and I have wrecked a hairspring at the re-fitting stage before. You would need to mark the hairspring so that it can be re-pinned at the same length.
 

jplotkin

NAWCC Member
May 8, 2016
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You mean I have to push out that brass pin (in the downward/left direction in the second photo)? And then push it back in to clamp hairspring back in place, after cleaning?

How horrid! What a terrible operation.

Would I use tweezers to do this? And why is there a groove in the stud that holds the hairspring and pin?

EDIT: OK, I tried this with tweezer, and the pin moved pretty easily actually. Still seems horrid.
 

svenedin

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Jan 28, 2010
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You mean I have to push out that brass pin (in the downward/left direction in the second photo)? And then push it back in to clamp hairspring back in place, after cleaning?

How horrid! What a terrible operation.

Would I use tweezers to do this? And why is there a groove in the stud that holds the hairspring and pin?
Yes it’s a tapered pin. It is horrid, it’s a very small pin! Let the professionals tell you how to do this safely. Don’t ask me!
 

D.th.munroe

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Feb 15, 2018
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On most of these you can actually push the pinning block out from the top (the pin you see above it on the cock) without unpinning the hairspring itself.
There used to be special tweezers with a 90° pin on side and a fork to support around the pinning block on the other for this.
The pin is just a friction fit in the cock, so after cleaning just push it back in and use the slot in it to turn it to the right place if it's not correct.
Dan
 

gmorse

NAWCC Member
Jan 7, 2011
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Hi J,

When you do it correctly, as Dan has suggested, you must be very careful if you don't have the special tweezers, since it's easy to slip and damage the balance spring. If it won't pop out easily, try turning it slightly from side to side first.

Regards,

Graham
 

jplotkin

NAWCC Member
May 8, 2016
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Philadelphia, PA
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Lacking the specialized tool do you recommend removing entire pinning block from cock or just pushing out pin? Pin seems to move pretty easily I’ve already found (under scope for observation).

Thanks for advice as usual.
 

jplotkin

NAWCC Member
May 8, 2016
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Philadelphia, PA
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Operation completely successful (photos below). Pin was quite easy to remove, and hairspring threaded out through hole easily enough. Balance assembly now cleaned, oiled, reassembled, running at about -1s/d after regulation.

Thanks for all your advice again!

removing-pin.jpeg loose-jewel.jpeg replaced.jpeg traces.png IMG_0652.jpg
 
Last edited:

gmorse

NAWCC Member
Jan 7, 2011
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Hi J,
Pin was quite easy to remove, and hairspring threaded out through hole easily enough.
Ideally, that pin would have a flat filed on the side nearest the spring, making it D sectioned, so that there's less tendency for the spring to be 'cupped' when the pin is driven home. It also makes it easier to turn the pin and spring together to bring it level.

Regards,

Graham
 
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