Two-piece mainspring on Omega pocket watch?

wmueller

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Hello everyone,

My first post here. I have enjoyed following all of the knowledge captured in this forum.

I am working on a vintage Omega pocket watch movement (caliber 40.6L.T2.15P). When I opened open the barrel yesterday, I encountered something I had not seen before. At first, it looked like the mainspring had broken just around the arbor. However, after further inspection, I noticed that the inner section of the mainspring wrapped around the arbor appeared to be attached to the outer section of the mainspring using some form of connector. I have attached a few photos for reference. I am relatively new to this and I am wondering if this was a standard mainspring design or this is a workaround that someone placed into watch during a previous repair/service.

I do need to replace the mainspring as it was damaged where it connects with the outer barrel. However, I would like to understand if I need to factor this inner section when I install the replacement. I am also looking for NOS mainspring parts for this movement but not having any luck. Any guidance or pointers are definitely appreciated.

thanks,

Wayne


IMG_0795.jpeg

IMG_0798.jpeg
 

gmorse

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Hi Wayne, and welcome to the forum,
I am wondering if this was a standard mainspring design or this is a workaround that someone placed into watch during a previous repair/service.
Yes, it certainly isn't a standard design, and I think you're being polite in calling it a workaround; others might call it a bodge, albeit an ingenious and apparently quite well-made one.

Regards,

Graham
 
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wmueller

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Graham,

Thank you for your response!

I think you're being polite in calling it a workaround; others might call it a bodge,
Ha! That was my first reaction, but like I said, I am new to this and didn't want to risk offending anyone if this is a common repair practice.

My next dilemma is ordering a replacement mainspring. Since this is not standard, is it safe to reference any of the dimensions from this existing mainspring? I did find a couple posts on other forums which mention mainspring specs for this movement but they are not consistent. Is there a parts list I can reference? Is there an equivalent to the Swigart book for vintage European-made pocket watches?

Thanks,

Wayne
 

gmorse

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Hi Wayne,
Is there an equivalent to the Swigart book for vintage European-made pocket watches?
No, not as such, but there are a lot of experienced people here who can probably point you in the right direction. There's also some very useful information in David Boettcher's website here regarding working out the correct size spring just from the barrel dimensions.

Regards,

Graham
 
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MrRoundel

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Interesting MS modification.
The Bestfit catalogs might be a good bet for sourcing the MS specifications. They are the Swigart-type catalog on steroids. The other possible source is Dr. Ranfft's movement data. His is a very handy site in identifying movements, etc. Good luck. Cheers.

Dr. Ranfft's movement data
 
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Dr. Jon

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FWIW the more accepted manner of fixing a mainspring broken at this end is to simply hold a small torch ot hot iren near the end to temper it, round it, punch a new hole and bend it into a tight enough curve to take the arbor. This is a lot easier and stronger.
 

wmueller

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MrRoundel gmorse. thanks for the pointers. I will check them out.

Dr. Jon What you describe is a bit beyond my experience (and toolset) at the moment. In addition, the section at the end of the mainspring that attaches to barrel is damaged. I am curious why it is more accepted practice to fix the mainspring as you describe versus replace? Given the "modification" that was made, wouldn't a new mainspring be safer/more reliable option?
 

gmorse

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Hi Wayne,
Given the "modification" that was made, wouldn't a new mainspring be safer/more reliable option?
Yes, always, as long as one of the correct size is available. It's not easy to make a new hooking in the centre of a spring, certainly harder than making one in the outer end. After all, we're not talking about original 18th century springs with signatures, which are a different consideration.

Regards,

Graham
 
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Dr. Jon

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The method requires that you be able to make a hole in the spring. A punch is easiest but not essential.

The key is the first step which is to temper the inner end. You can do this with a small butane forch of thee type slod in gas stations to light cigarettes and they typically cost less than $10. It is not a problem if you temper teh inner end too far.


Then it can be bent flat. If you have a punch jsu tdo it but the otehr method is to use a stake with a point over hole in teh rframe plate. make a dimple and file it to hrget a hole. The open teh hole with a needle file. I have done it both ways. SInce th end is fairly soft it is easy to bend it into teh curve to grab the inner arbor
 
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darrahg

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The method requires that you be able to make a hole in the spring. A punch is easiest but not essential.

The key is the first step which is to temper the inner end. You can do this with a small butane forch of thee type slod in gas stations to light cigarettes and they typically cost less than $10. It is not a problem if you temper teh inner end too far.


Then it can be bent flat. If you have a punch jsu tdo it but the otehr method is to use a stake with a point over hole in teh rframe plate. make a dimple and file it to hrget a hole. The open teh hole with a needle file. I have done it both ways. SInce th end is fairly soft it is easy to bend it into teh curve to grab the inner arbor
If you can't find an appropriate spring and the original seems repairable, here is a suggestion:
The main problem with working on the inner coil is that the rest of the main spring gets in the way. However, I make clamps out of two pieces of wood and two screws with butterfly wings (nuts) at each end. The wood pieces dimensions vary depending on the spring size I am working with and, basically, the vice keeps the rest of the main spring out of the way when tempering and punching the end. This process works well for me. Oh, and I don't care if I singe the wood pieces at all when tempering. Good luck on your project.
 

wmueller

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eri231 thank you for the Bestfit screenshot. I found a copy on eBay and will add it to my collection for future reference.

After some additional research, I did come across the Générale Ressorts catalog which has a lot of mainspring information for thousands of watch movements. These catalogs are published as multiple PDFs on the Cousins UK site. However, someone was kind enough to scan all these catalogs and created a single tab delimited file here: https://watchguy.co.uk/cgi-bin/mainsprings. I was able to locate my Omega pocket watch caliber and find the exact GR mainspring I needed. U sing this information, I also discovered that the existing mainspring had the wrong bridle. Good stuff!

Thanks to all for the guidance and pointers!
 
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