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  1. #1
    Registered user. ebrauns's Avatar
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    Question mainspring lifetimes

    All,

    How long should a mainspring last? If you have a ~100 year old (or older) watch, how likely is it that the mainspring will need to be replaced?

    Here's why I'm asking. In every pocket watch I have serviced/repaired (10 or so--I'm obviously a newbie), I can never get good balance amplitude. The best I can do is maybe ~140 deg, (it's usually less) even though everything else seems to check out:

    • I check the freedom of each wheel individually.
    • I check movement of the wheels in pairs.
    • I check for recoil of the escape wheel when the train is fully assembled.
    • I check the balance freedom by rotating it (with the pallet removed) by 270 deg, releasing it, and timing how long it will oscillate for. In all cases it will oscillate (dial up or dial down) for at least 1.5 minutes. In some cases it will oscillate for more than 3 minutes.
    • I check the pallet action by winding the watch and manually moving the lever to see how effectively it snaps over to the banking pins. I'll do this 30 times to make sure I test every tooth on each pallet.
    • I make sure the balance is poised.
    • I inspect the teeth and leaves of all the wheels, pivots, jewels, etc. using a 45x stereo microscope. As far as I can tell everything is in good condition (no bent pivots, broken teeth, chipped jewels, etc.).
    • To the best of my ability, I make sure that the watch is in beat. My "test" for this is that a small (1-2 deg) rotation of the hairspring in either direction degrades the performance of the watch. This may not be perfect, but it has to be pretty close (right?).
    • The watches all keep reasonable time when sitting stationary. I suspect that movement would compromise their ability to keep time due to the weak balance amplitude,
    • They will all run for at least 30 hours on a single full wind.


    I though maybe I was over oiling so I re-cleaned the movements and re-oiled them using less. This seems to have little or no effect on the performance. Applying a little pressure to the mainspring barrel to deliver more power always increases the balance amplitude, but I know that this is really not a good test of the mainspring. I've not taken the mainsprings out of their barrels for inspection because I don't have a winder, but looking at them in the barrels I see no obvious signs of damage or wear.

    By process of elimination I have to assume that the mainspring is the culprit. The fact that I have observed the same performance in every watch I have worked on is the reason for my original question. If mainsprings have long lifetimes, then it is statistically unlikely that all my movements have the same problem. But if they are not expected to perform well after 100 years or so, then it is reasonable to suspect that my problems are caused by faulty mainsprings.

    Any thoughts would be most appreciated. Thanks!

    Eric

  2. #2
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    Default Re: mainspring lifetimes (By: ebrauns)

    Hello Eric!

    A blue steel spring would have set after 100 years, I'm sure.

    Other than the checklist you already have, have a look at the side shake in the jewels and bushings. Wear on the pivots? Also, wear in the barrel arbor bushings and barrel bushings is common and can cause some nasty meshing issues leading to big power losses.

  3. #3
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    Default Re: mainspring lifetimes

    You could also buy a new mainspring for one of your watches and compare the amplitude with what you got from the old mainspring.

    Usually you can tell if a mainspring is set by the way it looks if you remove it from the barrel. A set mainspring "opens up" much less than a healthy mainspring.

    I would also guess that most of your watches has had the original mainspring replaced over time and the one you see is probably not as old as the watch.

    In particular you may find set mainsprings in broken watches. The owner often tried to wind it after it broke and left the mainspring fully wound.....
    Last edited by Skutt50; 07-10-2017 at 12:48 PM.

  4. #4
    Registered User Bohemian Bill's Avatar
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    Default Re: mainspring lifetimes (By: ebrauns)

    Eric..I had the same question when I started many years ago. What comes to mind is experience you gain as you successfully repair similar grade watches. You will eventually find the binding if you look hard enough. Have you tried a bench blower on each wheel installed between the plates? Some train issues may be in the mainspring barrel and arbor itself. I found that some 7 jewel watches are harder to get good balance amplitude than 17 to 21 jewel watches that I have repaired. With that being said you need to really need to check for excessive pivot hole wear, pivot condition and proper arbor end-shake that could cause binding. If you look closely there might be wrong wheels installed in the watch by the past repairman and later sold. You may have wound up with a cheap parts watch (Franken watch). I found many wrong pallet/escape wheel issues that cause low amplitude. I found this by exchanging pallet or escape wheel from a good running watch to find out the issue.
    Also replacement mainspring for each make, grade and jewel count needs to correspond with a thickness/ strength. For example Elgin 16size grade 291 takes a Elgin Cat 817 but there are 4 strengths available for 21 jewels to 7 jewels watches. The thickest mainspring available (.203mm) is for the 7 jewel and the thinnest mainspring thickness (.184mm) is for 21 jewel watches. This is what been explain to me by the old timer watchmakers. Good luck Bill

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    Default Re: mainspring lifetimes (By: ebrauns)

    Even a good mainspring, if it is left in the barrel and not removed, properly cleaned and lubricated, will not transmit the power that it would if it were clean and lubricated. If the mainspring is an old blue steel one, chances are very likely that it needs replacing.
    Samantha

  6. #6

    Default Re: mainspring lifetimes (By: Samantha)

    I always replace blue steel with alloy, whenever possible. (There are a few American watches for which alloy is impossible to find but, other than that, I use alloy.)

  7. #7
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    Default Re: mainspring lifetimes (By: ebrauns)

    You are doing a good job from your list but the mainspring has to come out of the barrel during a watch service. If it doesn't open up to at least 2 1/2 to 3 times the diameter of the barrel it is set and needs to be replaced. It is also very common to find that an incorrect mainspring has been installed in the past. Certainly not likely in all 10 you did but quite possible in a few.

    Roger

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    Registered user. ebrauns's Avatar
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    Default Re: mainspring lifetimes (By: pocketsrforwatches)

    Thanks for the replies. Here is what I have gathered from the responses so far.


    • I need to invest in a mainspring winder so that I can include proper cleaning and oiling of mainsprings when I service a watch. Skipping this step is a corner I should not be cutting.
    • It's likely--but not definitive--that the mainspring will need replaced in order for the watch to function optimally.
    • I still need to take more time and more care to ensure that there aren't problems within the train, escapement, etc. Even though I'm checking for the right things, I may not be detecting underlying faults.


    The responses have sparked a few new questions.


    1. When I look for mainsprings on Ebay, many of them appear to be sold already tightly coiled. Does this mean that it's possible to insert them without the aid of a winder? I ask because a mainspring is quite a bit cheaper than a winder. While I will ultimately invest in one, the path of least resistance initially would be to just pop in a new mainspring to see if the watch performs better. That way I'll have a better idea if I'm doing a decent job of servicing. But I can only take this route if I can insert the replacement without a winder.
    2. It would seem like buying a "new old stock" mainspring would not be advised since it is likely to have set over many years sitting on a shelf. Am I correct in assuming this? If so, I guess that means I need to look for alloy replacements (I assume that NOS mainsprings would be blue steel)?
    3. This may be the subject of another thread, but could some of my problems be due to my oil choice? Right now I'm using Moebius 8000 for everything (I hope that does not make anyone cringe). I realize that the experts recommend different oils for different parts of the movement, but I read that the 8000 is a good all around catch-all. I imagine that using slightly different oil types for different parts would improve performance, but that the improvement would only be marginal.


    Thanks again!

    Eric

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    Default Re: mainspring lifetimes (By: ebrauns)

    1 - If you have the correct mainspring for your watch you can normally push it into the barrel without unwinding. I would still recommend you get a winder since you are going to need it.......

    2 - Blue mainsprings have their problems. They can be set when you get them but you also have to look out for broken springs. Some are broken in their package and some break soon after installation. You can be lucky and get good old blue mainsprings but to be on the safe side you might want to avoid them if possible.

    3. One oil for everything is a bit optimistic. It also vairies with size of the watch. You need some grease for winding parts and then move down to lighter oils the closer you get to the balance wheel. I use Moebius 9020 and 9010 for most movement parts. Here is a link you can read up on the use of different Moebius oils: http://www.ofrei.com/page246.html

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    Default Re: mainspring lifetimes (By: ebrauns)

    Hi Eric,

    The problems with pushing springs straight into the barrels from their retaining rings are twofold; first you can't examine them properly before fitting them, and second you can't check their lubrication either.

    One of the main differences between the 8000 and 9000 ranges of Moebius oils is that the former are "natural" oils and the latter are synthetics, which don't deteriorate into gummy residues so readily and tend to stay where they're put. The right lubricant can make quite a difference. For example, using 9415 on the escape teeth and pallets can improve amplitude noticeably.

    Regards,

    Graham

    "Ut tensio, sic vis" - Robert Hooke

  11. #11

    Default Re: mainspring lifetimes (By: gmorse)

    Graham, would you mind sharing your technique for applying 9415?

  12. #12

    Default Re: mainspring lifetimes (By: Dave Coatsworth)

    Maybe it's because I'm working on Elgins from >50 years ago, using NOS mainsprings from about that same time, but rarely do I encounter a mainspring in a retaining ring small enough to pop into a barrel. This must be a new thing - and here, 'New' means 'within the last 50 years'.

  13. #13
    Registered User gmorse's Avatar
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    Default Re: mainspring lifetimes (By: Dave Coatsworth)

    Hi Dave,

    Since I mostly work on 18th and early 19th century movements, they're largely verges with the odd English lever and cylinder, each of which I find benefits from the special properties of 9415. On a verge I put a very small amount on each verge flag, on ratchet tooth levers I try and put some on the impulse plane of the exit pallet and let it work its way round, and on cylinders a very small amount on the outside of the cylinder, which again works its way onto the inside surface via the escape teeth. Even though Moebius claim the grease is really intended for high-beat movements it does make a difference even on escapements running at 14,400 or even less. I don't use epilame, I don't see that it has much advantage on these early movements, (and it's ridiculously expensive!).

    Regards,

    Graham

    "Ut tensio, sic vis" - Robert Hooke

  14. #14
    Registered user. ebrauns's Avatar
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    Default Re: mainspring lifetimes (By: gmorse)

    As usual, thanks for the replies, but (also as usual) they've sparked new questions. Hopefully they won't take the thread too far off topic.

    As I'm learning, I've taken a very conservative approach to oiling since it seems to me that too much oil is probably worse than not enough. Because of this, and because of the considerable debate over it, I have opted NOT to oil the pallet stones. However, in light of some of the replies to this thread, I decided to give it a shot. All I have at the moment is Moebius 8000. While I know that this is not intended for pallets, I went ahead and used it just as an experiment to see what happens. Lo and behold, the balance amplitude improved considerably! Still far short of 270 deg, but an improvement nonetheless; I'll be oiling pallet stones from now on. Now for my questions.


    1. Graham, you mention using 9415 on the stones. However, according to the BHI oiling guide, 9415 is for high speed escapements. For low speed (like 18000 vib/hr pocket watches), they recommend 941. How important of a distinction is this?
    2. After oiling the stones, I noticed that the balance swing is slightly asymmetric now (i.e., it swings maybe 10 deg or so more clockwise than anti-clockwise). I know that this is a symptom of being out of beat, but it was in beat before I oiled the stones. (My method for determining amplitude--since I don't have a timing machine--is to shoot a slow motion video with my phone that I can play back at half speed.) Is it possible that the asymmetric swing could be due to uneven oiling of the stones so that the impulse is more effective in one direction than the other? Or was the watch really out of beat all along, but it was harder to detect (using my method) when the amplitude was low?


    Eric

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    Registered User gmorse's Avatar
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    Default Re: mainspring lifetimes (By: ebrauns)

    Hi Eric,

    Although 9415 is recommended for higher speed escapements, (by Moebius as well as the BHI guide), I've found that it does make a difference on other escapements as I said earlier, and being a thixotropic grease it tends not to migrate where it isn't wanted.

    ...Or was the watch really out of beat all along, but it was harder to detect (using my method) when the amplitude was low?...
    With a low amplitude it certainly is harder to detect when it's out of beat. A small percentage of a small value will be an even smaller value! Even if you only oil one stone, the lubricant ends up on the other one as well as it's carried round on all the escape teeth.

    Regards,

    Graham

    "Ut tensio, sic vis" - Robert Hooke

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