Is this mainspring worn out?

[kibbler]

I'm doing a service on a very pretty 6s Elgin, and I got to taking out the mainspring, and it looks like this:

It seems like it uncoiled way too small, although I haven't worked on another 6s, only larger size 12/16/18 pocket watch movements.

Does that mean the spring is worn out and needs to be replaced?

Edit: here's the whole movement

Edited March 9, 2022 by kibbler
adding photo

[xyzzy]

Measure the amplitude.  But yes, that spring is worn out.

[AndyHull]

It does look pretty tired. If you can get the correct replacement, then I would change it, otherwise you may spend ages chasing low amplitude problems and erratic running only to have to strip the movement and replace it any way. At least if you replace it you know it is good, and if there are issues they lie elsewhere. I see the regulator is fully to one side, this may be because the spring is unable to maintain a good rate.

I did see one (old stock) on ebay, so this may give you the size, assuming it is the same movement. I'm not sure I would fit a new old stock one if there is a modern replacement available. What would other forum members suggest? Have they had any issues with new old stock springs? Do these things have a shelf life?

That is a nice looking movement, do you have any pictures of the watch?

 

Edited March 9, 2022 by AndyHull

[kibbler]

Is it better or worse to get a modern alloy mainspring over a NOS one?

 

https://www.jewelerssupplies.com/elgin-mainspring-6-size-MS-JA112.html

[oldhippy]

That spring needs to be replaced. If I could imagine myself as a mainspring that is me at the end of each day bloody knackered and ready for bed.  

[nickelsilver]

3 hours ago, kibbler said:

Is it better or worse to get a modern alloy mainspring over a NOS one?

 

https://www.jewelerssupplies.com/elgin-mainspring-6-size-MS-JA112.html

Alloy springs are less likely to break, and generally (not always) have a very slight increase in power for the same thickness. If you find an old stock Elgin alloy spring that's great- they pretty much invented the alloy and it's still produced and used for high tech stuff: Elgiloy.

 

To be honest that spring looks ok to me. An old rule of thumb is if it opens up bigger than twice the size of the barrel when taken out it's ok. But an alloy spring will be safer; if a mainspring breaks at full wind it can damage other parts of the gearing.

[KarlvonKoln]

I was on the fence here, to start.  Without the spring in front of me, it's a tough thing to really diagnose well.  As Nickelsilber stated, in the picture it doesn't *look* too bad.  I think it could have expanded a bit larger in the unwound state, judging by its barrel next to it, but it doesn't seem all that tired.
Yet, as we all know, how the spring makes the watch *perform* is the important issue, not how it looks.  Not knowing what its performance was before makes me want to give my default advice: if you can get an alloy replacement, I'd go for it.  An NOS alloy replacement is probably the ideal situation here.  Fewer worries for the future, and the performance of the watch will likely improve.

[kibbler]

2 hours ago, KarlvonKoln said:

Yet, as we all know, how the spring makes the watch *perform* is the important issue, not how it looks.  Not knowing what its performance was before makes me want to give my default advice: if you can get an alloy replacement, I'd go for it.

The watch was running very erratically, and would stop randomly.  Listening to the beat by ear, if it was a person, I would say they were having a heart attack.

On the other hand, the watch was pretty dirty, and who knows when the last time it was serviced.

I was thinking if the spring looked obviously tired, I would save the trouble and time of cleaning, reassembling, and diagnosing before ordering a mainspring.  I just don't know exactly what I'm looking for at this point.

[AndyHull]

I guess the only way to know if the old spring works is to give it a try.

I would clean everything, lubricate and reassemble. It shouldn't then be much of a chore to fit the old spring, test it, and if the results are poor, with low amplitude, despite the cleaning remove and replace the old spring.

 

[anilv]

If its your watch go ahead and reinstall it and see how it works. As long as it keeps time from morning to evening you're good.

If you are servicing this for money then replace the mainspring as a matter of course.

On a side note, this is a seven jewel movement so it will have higher friction and this translates into more mainspring power required.

Anilv

[Len33]

Personally, I wouldn't go to all the trouble of removing the old main spring and then putting it back in there again, because it will have seen many, many better days.

Replace it with a brand new one.