Can Mainsprings Be Rejuvenated?

Discussion in 'Clock Repair' started by darita, Jul 28, 2017.

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  1. darita

    darita Registered User

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    I'm having real trouble finding a mainspring for an alarm clock. If I can't find a replacement, can a MS be rejuvenated in any way? By the way, this is for my own collection and not for a customer, so it really doesn't have to be new.
     
  2. Willie X

    Willie X Registered User

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    I guess the short answer would be no. But, on the plus side, mainsprings are rarely the cause for a clock not running.
    Willie X
     
  3. RJSoftware

    RJSoftware Registered User

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    #3 RJSoftware, Jul 28, 2017
    Last edited: Jul 28, 2017
    It would be interesting to try. If you have the coil resting in a loose position, heat all of it up to red-hot (referred to as super-heat) then dunk the whole thing at once in oil, that might work good enough.

    In case you do not know, the mainspring is high carbon steel and in the process of making a spring the metal must reach super-heat(a dull red-hot) and then quenched right away. This causes the metal to become more crystalline/spring-like. If you use water it gets even more rigid, but I think too rigid. The oil is a slight compromise and a piece that has been crystalized will crack more often.

    So to add resilient character the piece that was water hardened, it is then shined up and re-heated till the piece turns blue. This re-heating is actually softening/annealing but adds strength or less apt to crack. I think that using oil is a shortcut else you may have to anneal/temper the whole piece.

    The act of shining up the metal by sanding/wire brushing is so that color change can be seen when annealing (the second heating). The desired color is blue for most strength. Some say you can skip the annealing by using oil on first dunk.

    RJ
     
  4. bangster

    bangster Moderator
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    #4 bangster, Jul 28, 2017
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    Nonono. Stretch the mainspring out full length 3 or 4 times and hold it stretched out for a few seconds each time. Sometimes this will remove enough "set" to make it work for a good long while. No guarantee, but I've seen it work.

    Or...hang it on a nail through the center coil, and attach a weight to the other end to keep it stretched for a while. While it's stretched, rub it down between thumb and forefinger. Same effect: eliminate "set".
     
  5. darita

    darita Registered User

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    Thanks RJ. Sounds like something you have to have experience with, to get it right. I only have one try. I was hoping I would be as simple as straightening out the MS, to regain some of it's potential.
     
  6. bangster

    bangster Moderator
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    What I said!

    Hardening and tempering a spring takes some experience and skill. I advise not trying it.
     
  7. roughbarked

    roughbarked Registered User

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    Seriously, I've rejuvenated many a spring by cutting a new hole for the barrel hook and this takes knowledge and skill of annealing and re-tempering. A whole mainspring would have to be done with equipment that no clock repairer has.
     
  8. darita

    darita Registered User

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    ...and how does this rejuvenate the mainspring?
     
  9. roughbarked

    roughbarked Registered User

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    It turns a useless mainspring into one that works again. An alarm clock with a set mainspring is something I've never seen but one with the ends broken is common enough.
     
  10. roughbarked

    roughbarked Registered User

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    No.
     
  11. darita

    darita Registered User

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    I'm sorry...I'm as dense as a post sometimes. I've got a used loop-end MS. What, exactly, would I have to do to this MS to rejuvenate it?
     
  12. Willie X

    Willie X Registered User

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    The "set" mainspring thing is pretty much a myth. Same as the "wound to tight" thing.
    I'm with Bangs, it would take at least an oven with a good thermocouple and a lot of experience with the same type spring to make any improvement. Just about all springs will spend at least 80% of there energy before the clock will stop.
    Experiment: Let your mainspring completely down and wind it back up, counting the turns. Run your clock until it stops and count the turns to wind it. If this last number isn't
    about 80% of the first number, you have a problem with your movement.
    Willie X
     
  13. Tinker Dwight

    Tinker Dwight Registered User

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    It would need to be tempered while stretched out. They usually do this
    with a continuous machine. It rolls along between rollers that separate the
    flames from the cooling and such.
    I've been told that one can completely unroll it and use a spring winder to wind
    it in the opposite side.
    Still for a properly tempered spring, if it has relaxed, it is because it has
    lots of little micro-fractures.
    It is not something you'd want to put in a barrel.
    Tinker Dwight
     
  14. Willie X

    Willie X Registered User

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    I have reversed several springs, as instructed by the great clock repair writer Huckabee. They all broke during the process or shortly after, so I wouldn't recommend this idea to anyone, especially if you have a spring that is not available.
    Willie X
     
  15. roughbarked

    roughbarked Registered User

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    Yes. The spring is run through heat and cooling not disimilar to pulling wire. It feasibly could be done but at great expense for one mainspring.
     
  16. TEACLOCKS

    TEACLOCKS Registered User
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    I knew a guy that re-ark leaf springs. (They would go flat)
    He said they don't lose there spring they lose there ark.
    So if you straighten the spring, when you rewind it you will put the ark back in it.
    What do you think:???::???:??
     
  17. kologha

    kologha Registered User

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    I have rejuvenated a number of springs from plus minus 100 year old clocks and can personally recommend the technique which I first saw in "The Clock Repairer's Handbook" by Laurie Penman 1985 page 143:


    "Incidentally a tired spring that has clearly been in place a long time can very often be given a new lease of life by straightening it out with the fingers. Obviously if the spring is new and become tired, there is a problem with it's strength (more properly it's 'temper') in which case there is no point in straining it again in this fashion. However, all springs lose a little of their facility to recover from the strain of being wound up, at each winding, and if the observed tiredness is a result of this, the spring may very well be preserved to give many more years of additional service."
     
  18. darita

    darita Registered User

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    Ah! That's where I remember seeing this! Thank you for pointing this out. I always wondered if this was truly the case, as it was stated by those with the most experience with these clocks and mainsprings.
     
  19. R. Croswell

    R. Croswell Registered User

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    I agree with Willie, "I guess the short answer would be no. But, on the plus side, mainsprings are rarely the cause for a clock not running". When a spring is stretched out straight (for whatever reason) it will likely end up with a larger relaxed diameter. Back in the clock it will initially provide a bit more power but I find the improvement is usually short lived. The greater concern is that the metal is being stressed beyond the yielding point (read that bent if you like) and we all know what happens when we bend a piece of metal back and forth beyond the point where it returns to its original shape. That's right, sooner or later its gonna bust!

    RC
     
  20. Willie X

    Willie X Registered User

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    Dari,
    I think we could be more helpful if the efforts were shifted toward finding you a new spring or troubleshooting your movement for a defect.
    Do you have the measurements for your spring? And, did you do the 'turns of power' thing I mentioned earlier?
    Willie X
     
  21. RJSoftware

    RJSoftware Registered User

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    The way I was looking at it is that it's only an alarm clock spring. So it's a small spring, might even be small enough to heat all at once with a propane torch. My thinking was at least it is worth a try. I've done the straightening trick and in general the results are very temporary. But I admit I have not bothered with the tighter inner coils, so it was not 100% straightened. Still I think the results are temporary.

    For an alarm clock mainspring you can often find at Goodwill or Salvation army the cheap Chinese plastic WIND UP alarm clocks. They make excellent donar clocks for parts.

    RJ
     
  22. Tinker Dwight

    Tinker Dwight Registered User

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    This won't work. You'll just be resetting the temper with
    the spring wound. You'd need to unwind it to temper it.
    I'm not sure how you'd do that without a long flame source
    and a long quenching tray to put it in.
    Tinker Dwight
     
  23. RJSoftware

    RJSoftware Registered User

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    Well, the terminology gets a bit mixed up when you say resetting the temper then that would be no.

    What I am saying is I would take it to super-heat and then quench in oil. Tempering is the second heating (as to my understanding) where the metal is first crystalized (super-heat and then water quenched) and then annealed to temper the metal in order to regain strength through the reduction of brittleness and resistance to breakage.

    My understanding is dunking from super-heat in oil instead of water skips the second step annealing process. The term Temper is I think reference to the result of annealing after a metal has been crystalized.

    I know that I can heat the whole coil with a propane torch to red hot. An alarm clock spring is relatively small.

     
  24. roughbarked

    roughbarked Registered User

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    Was his name Noah?

    - - - Updated - - -

    Which is why it is recommended to remove the mainspring from the barrel whilst cleaning it.
     
  25. roughbarked

    roughbarked Registered User

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    By doing this you will only wreck the spring. You will end up with a brittle spring that has no spring.
     
  26. RJSoftware

    RJSoftware Registered User

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    You tried it?

     
  27. roughbarked

    roughbarked Registered User

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    No. I have no need to. However, I can get an old mainspring and give it a go if you like. Think I will be wasting useable spring steel though.
     
  28. RJSoftware

    RJSoftware Registered User

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    #28 RJSoftware, Jul 29, 2017
    Last edited: Jul 29, 2017
    Not a like or dislike thing, just an experiment. See what is what, proofs in the pudding, "where's the beef" (Old Wendy's commercial slogan) you know.

    Ok, so I guess I gotta do it too...!

    Me, I got a whole file cabinet drawer full of springs from clocks. I keep them just in case. Also they make good clock hands.

    I guess to test the results might be an issue. I assume that by your response that the spring steel will just end up worse more brittle or weaker -which ever.

    But, does that mean I have to start with a weak/set one in the first place. To compare for improvement? I think not, the ideal being to test if treating is compromising/destroying. So it shouldn't matter what condition the spring is in, in the first place. Just to test if the process makes things worse.

    So, if the test is just to see if the metal becomes weaker, then that is easy test and I can use a small segment and weight test it before and after. Just has to be consistent between the two.

    Then there is the issue of how many times the spring will maintain springy-ness. So how many times will it repeatedly bend before it starts to give out (set) or snap/break.

    Keep in mind that after I get the piece rigid, I can anneal as much as I want to. And if oil doesn't do the job then maybe water crystalize and then annealing.

    I know that 500 degrees is the temperature of blue. So I don't even need to shine nothing up. I don't want to bother with scrubbing both sides of mainspring hey. :)

    I suppose I could bend two pieces same length, one treated and one not to test which gives out quickest (or actually to see if the treatment causes spring to fail(set) faster.

    If you attempt anything let me know.

    RJ
     
  29. bangster

    bangster Moderator
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    I find this a remarkable claim. I think it's been empirically proven that a spring held compressed over a long period will have a diminished ability to expand. I could be wrong --can't cite any studies-- but the experiences of both clocksmiths and spring phonograph repairmen confirm it.

    This is a different issue from whether stretching can extend springiness. My experience is that it can, for a limited period. But aside from that issue, I think it's unquestioned that a spring, held compressed over a long period, will have metallurgical effects resulting in diminished ability to expand.
     
  30. RJSoftware

    RJSoftware Registered User

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    #30 RJSoftware, Jul 30, 2017
    Last edited: Jul 30, 2017
    I think what Willie X is saying is that the "set mainspring" is about the last resort. Because if you think about it you can wind up a clock with weak/set mainspring fully wound and it should surely have as much or more power than a new mainspring has with some wind on it...

    I sort of look at it that way, but I am still curious about doing the rejuvenating test. Just for curiosity sake.

    But in general there is usually something wrong with the train. The only time I ever buy new mainsprings is when the old one keeps cracking over and over again.

    When it comes down to a movement that I end up fiddling with over and over because I'm getting no good results I will go the mainspring route. I'll even move bushing holes to correct depth or replace questionable pinions/trundles before I start on the mainspring.

    Like it was said here, a clock has to get down to 20% of power before it's expected to stop. Hard to imagine any kind of set mainspring really won't push at least 50% of the full winded power no matter how old/set the spring.

    Some cheat (I have) and go extra strength to overpower the movement into submission. I did it on a snoopy alarm clock. thing was a pain. It was probably wrong thing to do but it was nice seeing that sucker take off robust instead of just eeking along. The new (old) spring was heavier gauge.

    RJ

     
  31. bangster

    bangster Moderator
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    So far as I know, the only thing a set mainspring will affect, by itself, is the length of the run. But combined with power-robbing issues that it can't overcome, it can contribute to other problems. We don't exactly know what the OP's clock is doing or not doing that might trace to the mainspring.
     
  32. Bruce Alexander

    Bruce Alexander Registered User
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    Also, I think that a set mainspring's torque curve is not nearly as flat as one which is not set. That may be what you're stating bangster. I've measured the bph on a ST 113 with set and new mainsprings. It's easier to make an "all else being equal" comparison since the front plate is split and the springs can be changed without affecting the rest of the movement. I found that there was a quicker drop off of torque as measured by bph before the readings leveled off, and the set springs entered the drop off towards the end of the wind cycle earlier as well. This torque-curve effect can be minimized to an "insignificant" level with more frequent winding or the owner may just view as insignificant the fact that the clock loses a few more minutes by the end of the wind cycle. A clock may run okay with a set mainspring, but all else being equal it probably just won't run as well. Most mechanical clocks I've run across don't have a split plate and changing out mainsprings means complete disassembly.
     
  33. bangster

    bangster Moderator
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    That too. What they call "increased isochronal error".
     
  34. Bruce Alexander

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    Here were the results I observed
    312125.jpg
     

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  35. Willie X

    Willie X Registered User

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    Dari,
    I hope you can jump back in with those measurements and 'turns of power' observations. Otherwise, this thread is in th dumper. ☺
    Willie X
     
  36. Bruce Alexander

    Bruce Alexander Registered User
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    It also occurred to me that my tests were conducted on a movement with a dead-beat escapement. I suspect that a movement with a recoil escapement would show a more pronounced effect on its rate.
     
  37. R. Croswell

    R. Croswell Registered User

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    Interesting experiment and observations. We frequently hear the term "set" and in your chart you referred to "old springs". I'm wondering just how old and "set" the old springs were.
     
  38. Willie X

    Willie X Registered User

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    RC,
    Me too. And, I'm wondering if the old spring was well serviced. Actually it's a surprising linearity for 7 days between day 4 and 11. You might get more variation than that from two new springs, especially if they were from different manufacturers. I would guess it was a recoil escapement, as they vary more with small changes in power.
    TAT,
    Thanks for taking the time to make such a chart, a very interesting study.
    Willie X
     
  39. shutterbug

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    Also notable is that the percentage of time deviation is pretty small.
     
  40. Bruce Alexander

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    #40 Bruce Alexander, Jul 31, 2017
    Last edited by a moderator: Dec 15, 2017
    I took photos, but I didn't take notes.
    This comparison was done about 3 1/2 years ago so to the best of my recollection these were the circumstances:
    We should also keep in mind that these are barreled springs.

    I was preparing the Seth Thomas Chime No. 70 for sale and wanted to restore it to factory performance to the best of my ability.
    I did complete the overhaul reinstalling the cleaned, inspected and lubricated "old" mainsprings. I don't fully stretch out mainsprings when I service them. I typically stretch and work on about one coil at a time by allowing the mainspring to coil "behind" me. The end result is that the spring steel pretty much remains in an as-found state. The inner few coils typically are somewhat expanded by the process but the spring is not "rejuvenated".

    I ran the movement on a test stand for about a week recording the BPH about the same time each day give or take a couple of hours. I thought the drop off was significant and although the isochronal error was relatively small when viewed as a percentage of the total, a variance of 1 beat per hour resulted in an error of 9 seconds per day (as per Jeff Hamilton's Beat Book Chart).

    The target rate for a Seth Thomas No. 113 is 9894.86 BPH. The movement was regulated very close to that rate, but by days five and six it was off by 8 BPH which meant it was losing about 72 (8x9) seconds per day. By days seven and eight it off by 17 BPH and thus was losing 153 seconds per day. Totaling those error rates up, by the end of the winding cycle it had lost an estimated six minutes. This was all calculated and not observed on the clock's dial because the movement was still on the stand. If I had planned to keep the clock in my collection, I may have been happy with that, choosing to either make the correction at the end of the week or wind it twice weekly.

    Since I was going to sell the clock I decided to order new mainsprings and continued taking daily readings while I waited for them. When the springs arrived, I cleaned, inspected, lubricated (using Keystone Lube) and installed them normally. I did regulate the movement to target rate and repeated the measurements for side by side comparison. I was surprised to find that both springs resulted in a slight increase in rate during the first day or two, but as I suspected, the new springs had a much flatter torque curve as measured by BPH. By day eight the new spring was still at the target rate and only started to vary significantly after day ten.

    Here's a photo of two of the old springs still in the barrels with the new springs as received for comparison. Note the number of coils between the center coils and the outer most constrained coil. As I recall, by some definitions, a barreled spring is set if it takes more than a couple of spirals to span that distance. Another definition that I've come across states that a mainspring is set if it only expands to twice or less the diameter of the barrel.

    312149.jpg

    Here's a photo of the new and old springs fully relaxed with the barrel next to them
    266654.jpg

    Here's a photo of one of the old mainsprings still in the barrel with a new mainspring installed in a barrel as well. These comparisons are between the time and strike barrels which use identical springs.
    312152.jpg

    Here's a photo of the fully assembled Chime No. 70

    266655.jpg

    Willie, you're very welcome. I'm glad that you found the info interesting. Thank you! 312149.jpg 312152.jpg
     

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  41. bruce linde

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    my clock mentor just did this with the mainspring in a small turret clock, with a horizontal movement and platform mechanism.

    he reports noticeably more power even though he wasn't able to completely stretch out the mainspring because he simply didn't have a big enough quenching tray.

    and, to corroborate comments by rc and willie, the mainspring turned out to NOT be the problem... but he did get more power.
     
  42. Bruce Alexander

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    Hope that I've addressed your curiosity RC. I suppose it would be good to know how to "rejuvenate" a rare mainspring which is not easily replaced. I suspect that any improvement will be relatively short-lived but if the clock is not part of your collection, there is really no way to know how long, and how well the torque curve will hold over the course of the movement's winding cycle. I also suspect that consistency of rejuvenation results will be hard to achieve for many of us (it certainly would be for me), particularly if it is only done as a last resort.
     
  43. TEACLOCKS

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  44. kologha

    kologha Registered User

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    Regarding the longevity of straightening an old mainspring, I have done it on two of my clocks which are both over 100 years old. Before I carried out the operation both clocks tended to keep time for a day or so and would then begin to gain as the week wore on. Both clocks have the original springs and after straightening the springs which I did over two years ago, both clocks now keep time to within one minute a week. I firmly believe that straightening an old spring does give it a new lease of life. I have done it to a few other clocks which I have serviced as well and received favourable reports from their owners.
     
  45. Bruce Alexander

    Bruce Alexander Registered User
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    Two plus years sounds like a good start. Still, straightening out 100 year old springs to re-use (or even just to service) them can reportedly be very dangerous and is not something that I would choose to do routinely.
     
  46. kologha

    kologha Registered User

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    I have faith in old German technology (except for Hermle) as most of the clocks I work on fall into that genre. I am aware of reports of broken springs and even springs that break while removing them, but havent personally come across one. However I am very careful when removing and opening a spring just in case it is one of those!
     
  47. Tinker Dwight

    Tinker Dwight Registered User

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    I think many of the cases of broken spring while taking them out
    is that the spring layers are glues together with age.
    When they suddenly let loose, the shock breaks the spring.
    Tinker Dwight
     
  48. Willie X

    Willie X Registered User

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    TAT,
    I've been pulling springs out flat to clean and service them for about 30 years. This procedure has worked very well for me and I have recommended it highly to others. I always thought that the "rejuvenation" was due to the clean smooth and well lubed surfaces. Yes the spring does open up a bit but that is temporary.
    The big spiral of a new spring is also temporary.
    Willie X
     
  49. Bruce Alexander

    Bruce Alexander Registered User
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    Hey Willie,

    Here is an interesting mb thread on the subject of restoring set mainsprings with heat. It includes a post by J.C. Losch:

    I agree that the expansion of a cleaned (as well as a new) spring seems to be temporary. I've noticed that the minor expansion of inner coils due to my sectional/coil servicing technique readily disappear after the spring has been installed and cycled a few times. I also fully agree with your point concerning the proper and thorough servicing of a spring to be of primary importance.

    I know that a newly manufactured mainspring can break when you're installing it for the first time. I try not to be dogmatic in my approach so I'll consider opening a spring up and perhaps hanging a weight on it as described by bangster in the future if the spring seems "set" and if I can not find a suitable replacement. Of course there are instances where an original mainspring itself holds unique value and thus should be preserved if at all possible.

    So with those exceptions, I still think that replacement is the surest way to restore an adequate power/torque curve to a movement. The cost is usually not that significant (but in a declining market it's ain't nothing either). In the short time I've been working with clocks I've seen a few of Seth Thomas 113 movements which have suffered damage to the Chime Train due to a mainspring failure. Perhaps that has colored my judgement and of course I definitely don't want to have to split the plates twice due to isochronal error during a test period if I can avoid it. For these reasons my first impulse is to replace a questionable mainspring with a newly manufactured one of first quality.
     
  50. Willie X

    Willie X Registered User

    Feb 9, 2008
    12,469
    856
    113
    WOW,
    Your conventional wisdom made a lot of sence when mainsprings were nearly always good, inexpensive, and readily availabe in all sizes. Things are a lot different now and many more repairers are keeping the old spring for the obvious reasions
    AFAIK, I am holding the record for run time on an American
    8-Day clock. I have a photo of the spring somewhere if anyone wants to see it.
    Willie X
     

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