Mainspring keeps slipping from barrel arbor

[GeorgeC]

I am in need of some advice on how to get a mainspring working in a Waltham 0s hunting case.  This is a complete restoration of a rusted watch - spent way too much time on it already.  I have it cleaned up now and in process of finalizing assembly but the mainspring I have installed keeps slipping from the center hub/barrel arbor.  Hook of arbor hub appears fine and the tail of the mainspring is hooked well in the side wall of the barrel.  I have installed 2 new but old inventory mainsprings and wanted to know if this may be the problem and I just need a new fresh mspg?  I have installed many mainsprings but this one is terrible.  I am using a pocket mainspring winder to install. 

movt serial #9535224

You can see my original mainspring below.  I will add a picture of the inside of the mainspring barrel when I get the chance.

Thanks for any help,

George

Edited January 26, 2018 by GeorgeC

[Ishima]

It sounds like its put in the wrong way up, at least that's all that comes to mind for me, even if it's a bit silly.

Edited January 26, 2018 by Ishima

[GeorgeC]

Thanks, but I have taken purpose with installation prior to winding in the installer, to ensure correct counter clockwise installation, which is correct.

[mousekar]

This isn’t going to be very helpful for you, but I have the same size movement, from the same company, with the same problem! I know there are 4 different model numbers of mainspring that are attributed to the Os Waltham. You have the smallest in width. I started with the largest (2.0 mm) and then realized that it was too large for my barrel. I tried to measure the barrel wall and with that went with the next size (1.7mm). I may still have the wrong size. And I’m not sure, other than trial and error, how to tell what the right mainspring is.

I’ve also read that you can put a small bend at the outer end of the spring just below the hole (bend it in, towards the spring) and that will help it hook better. Haven’t tried that yet. I’m not experienced enough to know which end is slipping. I’m not a big fan of the way they do the arbor, you can’t see how it’s hooking to the mainspring.

Hopefully an answer will come across here!!

 

 

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[khunter]

If the hook on the barrel arbor is in good shape as you stated, it may be that the spring is just a bit too "sprung" around the arbor. You can gently tighten the inner coil with a pair of smooth jaw needle nose pliers to make it fit tighter around the arbor. I've found some NOS springs that the very inner tip is actually curved too much, past the hole, that makes the spring sit off the arbor nearest the hook and it wont engage. Flattening this area slightly will also let the spring sit right on the arbor. Being a 0 size you'll have to use great care, not much material to work with. Last option is to try a different arbor.

[GeorgeC]

I came across this forum post with the same issue here http://forums.watchuseek.com/f6/mainspring-install-help-1976050.html

 

This repair person states he files a chamfer in the end.  I suspect creating the 'knife edge' closest to the barrel hook.   https://mb.nawcc.org/threads/cant-replace-mainsprings-in-waltham-size-0.88515/  

[khunter]

18 minutes ago, GeorgeC said:

I came across this forum post with the same issue here http://forums.watchuseek.com/f6/mainspring-install-help-1976050.html

 

This repair person states he files a chamfer in the end.  I suspect creating the 'knife edge' closest to the barrel hook.   https://mb.nawcc.org/threads/cant-replace-mainsprings-in-waltham-size-0.88515/  

I believe what they are talking about is a mainspring barrel with the hook on the inside of the barrel, not the arbor. I wouldn't file on the spring as you would likely introduce a weak point in it. If nothing else I would check the arbor hook under high magnification and make sure the engaging side is not worn. If it is you may be able to square it back up with a diamond file.

[azkid]

FWIW, I have had to slightly adjust the cuvature of NOS Elgin springs I have replaced in one 6S and one 12S movement to get them close enough to the arbor to reliably snap into place and stay hooked.

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[azkid]

PS: Elgin barrels and covers I have seen have a slot, as well as a nub on the barrel inside wall to capture the outside end of the mainspring. If yours has this I cannot see how it could slip on the outside.

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[khunter]

7 minutes ago, azkid said:

PS: Elgin barrels and covers I have seen have a slot, as well as a nub on the barrel inside wall to capture the outside end of the mainspring. If yours has this I cannot see how it could slip on the outside.

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The OP said it's slipping off the arbor, not the barrel wall....

[azkid]

The OP said it's slipping off the arbor, not the barrel wall....

Apologies. The PS was directed at mousekar.

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[mousekar]

Apologies. The PS was directed at mousekar.

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Hey thank you for the advice. You are correct about the Elgin’s as I have worked on those too. But mine as well as the OP’s is slipping on a Waltham. If you’ve had experience with them as well, I’d love to hear it.
Cheers mate!
mousekar


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[azkid]

Hey thank you for the advice. You are correct about the Elgin’s as I have worked on those too. But mine as well as the OP’s is slipping on a Waltham. If you’ve had experience with them as well, I’d love to hear it.
Cheers mate!
mousekar


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Sadly, no Waltham experience yet

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[GeorgeC]

Restored, looking and running good.





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[azkid]

Wonderful! Good work there. Funny, I just ran into this problem again on anothrr 6S Elgin. [emoji16]