Restoring a Mainspring Using Heat?

Discussion in 'Clock Repair' started by Richard Barkey, Feb 15, 2010.

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  1. Richard Barkey

    Richard Barkey Registered User
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    While at an NAWCC chapter meeting yesterday I overheard something I wanted a second opinion on.

    One member told another that he takes old mainsprings that are weak, (sprung), and stretches them out by putting one end in a vice and pulls on the other. He then puts the spring in a 400 degree oven for several hours. The spring is then cooled to air temperature slowly without water or oil. This procedure is supposed to restore the strength of the spring and avoid the cost of replacing it.

    Is this a recommended procedure for restoring an old spring… or would the proper procedure be to replace it with new?

    I would appreciate your comments / suggestions.

    Richard.
     
  2. Kevin W.

    Kevin W. Registered User
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    Never heard of this method before.If the spring needed replacing i would just replace it.
     
  3. harold bain

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    I don't think I've ever heard this method before, Richard. I know I replace a lot fewer springs than most repairmen. It sounds like it may be worth some experimenting next time someone is thinking of replacing a "set" spring. I can't think of a good reason why it wouldn't help.
     
  4. Scottie-TX

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    I can't imagine a temp as low as 400 having any effect on steel.
     
  5. bangster

    bangster Moderator
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    I suspect the theory is that, after the spring is stretched, to approximate its original shape, the heat will allow the molecules to relax into that shape.

    Whether the theory is correct, I have no idea. :confused:

    bangster
     
  6. leeinv66

    leeinv66 Moderator
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    I had several (four) mainsprings shatter on me within a month a while ago and the only reason I could come up with for this happening was I had started using and old toaster oven to dry parts at that time. Needless to say, I stopped drying the springs in the oven and have not had another spring shatter. Coincidence? May be, but I wouldn’t recommend putting springs in an oven.
     
  7. shutterbug

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    I agree that 400 degrees is way too cold to restore temper to a spring. In principle, I think the idea is sound. However, I'm pretty sure the spring would have to be coiled tightly, then heated to at least double what the repairman recommended. Cooling slowly works for me. Often it's the rapid cooling, like an alcohol bath, that causes mainsprings to break under pressure.
     
  8. Mike Phelan

    Mike Phelan Registered User

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    You cannot temper steel without hardening it first, and that requires heating to a bright red for several seconds then cooling in liquid immediately.

    Then you temper by heating to the correct point by watching the colour, and that is quite critical.

    Worth trying the above, but I'm sceptical, and I would not bother trying it with a mainspring.
     
  9. Lynne Gillette

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    My thoughts are on the same wavelength as Mike's. One problem that quickly comes to mind is the molecular corrosion that occurs in the steel. That would not be corrected by applying low heat.
    I did have some small success with reworking brass mainsprings used in early American clocks by running through a rolling mill, but not enough to make it worth the effort.
    Lynne
     
  10. bangster

    bangster Moderator
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    We know that stretching a set mainspring will temporarily restore some of its power. The question is whether baking at 400° (F) would enhance that.

    I'm dubious, but an empirical test wouldn't hurt. Nature can hold some surprises.

    bangster
     
  11. Dave B

    Dave B Banned

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    I don'T know that 400 degrees (I assume Farenheit) is hot enough to affect a spring one way or the other. I DO know, though, that in the past they have had problems on drilling rigs in the Alaskan North Slopes, where temperatures are known to drop well below Zero Farenheit and springs shattered without warning. I also tend to follow the theory that the steel has to be at a temperature that affects the molecules to change the way it reacts at room temperature. Just what that temperature is, exactly, I am not sure. We all know that red heat will, for lack of a better description, "free" the molecules to the extent that they change the compositional structure. Perhaps it is possible to excite the outer rings of electrons at a lower temperature, provided the temperature is maintained long enough. Perhaps there is a moleculer physcist on here who can shed some light on this discussion.
     
  12. Thyme

    Thyme Banned

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    I see that some find the theoretical aspects of this as an entertaining, hypothetical discussion. That's fine, but my comments will address the practicality of the suggestion instead.

    I can't fathom why you wouldn't just simply replace the spring. Let's hope that it's your own clock and you won't invite the wrath of a paying customer with this oddball experimentation. Even so, by the time you remove the movement from the case, tie down the spring, open the movement, remove the spring, uncoil it, tinker with this kooky oven baking process, and reverse all the steps to reassemble everything, you will have spent at least several hours on the project.

    What is a new mainspring worth? About $10 on average? What is your time worth? Skilled labor is worth more than $10 per hour, isn't it? Isn't this false economy? :?|

    Even if you have nothing else to do but tinker all day, at best you will end up with keeping an old (less than potent?) spring in use. Even if this dubious suggestion is workable, the questionable old spring will probably fail sooner than a new spring would. And if it doesn't hold up, you're going to have to do the job all over again properly - with a new spring.
     
  13. bangster

    bangster Moderator
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    Not everyone has access to a convenient source of new replacement springs.
     
  14. Thyme

    Thyme Banned

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    We all know who the mail order suppliers are by now. Anyone who doesn't is probably not frequenting clock meets (which is how this thread began). In effect, we all have the same access to the same suppliers.
     
  15. bangster

    bangster Moderator
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    Not all of us live in the North America or the UK.
     
  16. leeinv66

    leeinv66 Moderator
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    Yes Bangster, when you have to add 50 bucks postage to your online orders or pay double the price to local suppliers, things are not so cheap for some of us!
     
  17. Thyme

    Thyme Banned

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    Well, you do. You claim to be in Utah.

    The original post began:
    This is predominantly a North American list, and the proposal was made by someone who obviously was from America. As I said, is isn't as if a clock repairer in the US can't find new springs available. The topic of the thread is not about whether mainsprings are difficult to obtain in other countries.
     
  18. leeinv66

    leeinv66 Moderator
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    And the award for promoting the Global discussion of Horology goes to…….:eek:
     
  19. Mike Phelan

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  20. bangster

    bangster Moderator
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    The topic isn't even about replacing mainsprings. It's whether a certain technique is effective.
     
  21. Thyme

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    It's also about whether it is worth doing it, because the whole intent of the proposition is that of being an alternative to replacing the spring. Other than as a theoretical, experimental exercise, the reason for suggesting it is to enable the repairer to make do with the old spring. Thus the idea may be inherently attractive to someone who is too cheap to buy a new spring.
     
  22. RJSoftware

    RJSoftware Registered User

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    It's always good to know what works.
    RJ
     
  23. leeinv66

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    This reads as presumptuous and self-serving logic to me Thyme. Obviously the reason for suggesting this method is to enable the repairer to make do with the old spring. However, while I would not use this method, I am sure there are reasons other than cheapness why it may be desirable in some circumstances. At the very least it is worth consider the possibility.

    Using this same line of logic, one could easily come up with alternative offensive theories on why using this method would be inherently unattractive. For example, the reason this method is inherently unattractive to some repairers is that they do not have the skill to do anything more than replace parts. Or, the reason this method is inherently unattractive to some repairers is that they miss out on the mark-up they normally put on replacement parts.

    Remember, I have put these forward as examples only, as I would not desire to further my line of argument in any thread by disparaging or belittling the point of view put forward by others.
     
  24. bangster

    bangster Moderator
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    If a spring could be made perfectly good using the procedure, why replace it with a new one?
     
  25. Thyme

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    So, from what you say, my pointing that out makes it "presumptuous and self-serving'. To you, of course, that seems to be the case, for you have already been allowed to try to steer this discussion into the realm of global relations rather than focusing on a comment that was made in America to American practitioners of repair. My subsequent comments addressed that aspect from that singular perspective - not whether springs were readily available elsewhere, globally. You took offense where none was intended and are still extending an irrelevant point.

    I agree. I never said my comment was the sole reason why someone would try this, did I? I could name a valid reason, but I will not make your case for you.

    Instead of being contentious, why don't you tell us why you "would not use this method"? Perhaps we could find some common ground of agreement, but I have reasonable doubt that you would be willing.

    So why would you want to introduce "offensive" theories other than to be contentious? A conscientious repairer would err on the side of caution with renewal of a defective spring. It is easy to err in actuality by disregarding caution in retaining a defective spring, especially if it is being done to save a few dollars, rationalized by an unfounded theory.

    If we return to the words of the original post we find this: "One member told another that he takes old mainsprings that are weak, (sprung), and stretches them out by putting one end in a vice and pulls on the other..." (etc.)

    What do the words "weak" and "sprung" mean? Can we agree that this spring as described IS by definition DEFECTIVE? Can we agree that replacing it is warranted (not merely on a whim), and is not being done for reasons of incompetence (although, to the contrary, replacement would be both prudent and competent) nor merely an attempt at bill padding (as your cynical suggestions imply)?

    I said what I did and I stand by it: those repairers who would desire to save a few dollars by trying to salvage a defective spring will find this proposed, theoritical "fix" of interest to them. That comment, in itself, does not disparage or belittle "the point of view put forward by others" - unless perhaps they are of that ilk, and that is their motive.

    I suggest you not propound lines of argument if you have no genuine belief in them other than the ostensible purpose being contentious with me.
    -> posts merged by system <-
    When it is proven to be "perfectly good" beyond reasonable doubt, it will deserve endorsement. Until then...
     
  26. harold bain

    harold bain Registered User
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    Lets try to focus on the question presented by Richard. A properly done rebuild of the movement will likely give the old spring a new lease on life, as much less power should be required to run the clock, than what was needed shortly before it quit. Baking the spring may not have accomplished anything. Sort of like backwoods herbal medicines, many don't do much good, but like placibos, help give the patient a good feeling.
     
  27. leeinv66

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    Instead of being contentious, why don't you tell us why you "would not use this method"? Perhaps we could find some common ground of agreement, but I have reasonable doubt that you would be willing.

    I'm not sure why this would be Thyme:confused: I am all ways willing to share what I think. And I believe I did list my reason in an earlier post to this thread. But to repeat myself, I believe this process makes the springs brittle and this can lead to them shattering. Another reason I doubt this method comes from my own experience with re-set coil and leaf springs in cars. While freshly re-set springs exhibit improved performance, this improvement is short lived and the springs soon return to their previous condition. I may be wrong in my assumptions, but this is how it seems to me.
     
  28. bangster

    bangster Moderator
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    What would be the best way to actually test the procedure?
     
  29. leeinv66

    leeinv66 Moderator
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    Perhaps a fishing scale suspended over a spring winder? With the winder fixed to a bench you could hook the spring to the scale and wind the winder a few turns. I would think you would get a different reading for the same amount of turns if there had been a change in the strength of the spring. But, I’m only guessing.:)
     
  30. Lynne Gillette

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    I never bothered trying this heat method when I was experimenting with mainspring restoration because I knew enough about steel. Some things I did look into were some of the common wive's tales and found most provided a temporary fix at best.
    These were things like fully extending a set mainspring and expecting it to be returned to full power, reverse winding a set spring,etc. The majority of the time they were really short term effects. Occasionally, just by the luck of the draw and the proper alignment of the planets you encounter one that works! This usually happens when a novice is tinkering around and then the wive's tale regains it's 15 seconds of fame!
    If you were a museum conservator or a purist you could be satisfied with the temporary results achieved IF you were saving an original mainspring. You would have to be satisfied with a clock that needed more frequent winding or having an original clock.
    If you are in the world of clock repair it is a different story. Most customers expect an eight day clock to run a full week. These old wive's approaches will seldom produce the desired result.
    Every craft has them. Problem with your car? Maybe the engine is lugging? Take it out on the expressway and open her up! Blast that problem out the exhaust pipe! Think you have a problem with the starter? Bang it with a hammer! Sometimes they work, most of the time you are calling AAA's!
    I'm not an old stick in the mud! I am from the school of "while everyone is telling me it can't be done, I am completing the job"!
    "Insanity is doing the same thing over and over again and expecting different results"!A.E.
     
  31. hoo-boy

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    Shying away from THE discussions:eek:! BUT I truly believe that to revamp a spring you would have to duplicate the origanal methods. Start by annealing, than hardening and then by tempering! Only justified IF not able to obtain a new spring whatever the reason! ...hoo-boy (trying to play NICE!:D)
     
  32. cazboy

    cazboy Registered User

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    Two points:
    1. Once you stretch a spring to its full 96" with one end in a vice, how does one fit it into an oven without allowing it to recoil?
    2. I recently read a post by John C. Losch (maybe it was here on this board), whose opinions I would treat as gospel, that he treats a weak mainspring by work-hardening it along its entire length (except for the innermost coils) by the unbelievably tedious process of striking it with a cylindrical hammer on an anvil, bit-by-bit, until the length has been hammered. I don't think he described the hammer's shape explicitly, but I got the impression it was like the side of a hardened cylinder so the whole width of the spring received a hammering stroke at a time. But since the spring is long, it must be hammered many, many times! And to top it off, he mentioned that if you hold the hammer at an angle, you'd put dents into the spring at that point so it must be held perfectly even the whole process.
     
  33. bangster

    bangster Moderator
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    Would have to be repeated over an (unknown) period of time. As Lynn points out, stretching a mainspring will temporarily restore some power to it. The heating is supposed to make the restoration permanent. At least, I think that's what it's supposed to do. At what point in the series of tests could we say, "OK, it's permanent" rather than "More tests are needed"?

    bangster
     
  34. Thyme

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    Do you mean to test to see whether the procedure is effective? As with most things, "the proof of the pudding is in the eating." The empirical test is to reinstall it in the clock and see whether there is any improvement, or whether it behaves any differently (reverts to its previous state or worsens) over time.
     
  35. bangster

    bangster Moderator
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    Over how much time?
     
  36. Kevin W.

    Kevin W. Registered User
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    Maybe just see if it would run a week or not, say a 8 day American clock for example.
     
  37. RJSoftware

    RJSoftware Registered User

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    Instead of an 8 day, why not a 30 hour. A spring is a spring, metal is metal.

    If the daily duration (say 24 hour insted of 30) proved successful, it would still have to prove longevity in repeated use.

    So for a 30 hour clock maybe a couple of weeks use would suffice. That would be sufficient I think to show that the fix was better than temporary.

    Comparably testing an 8 day

    8(7) days X 14 =98 days. So that is more testing time than I care to bother with.

    A 30 hour spring is smaller and easier to deal with. I'm sure one of us would have an alarm clock with sprung spring to test this out.

    Thing that is interesting about this to me, is that the low 400 degrees might be enough to cause the desired molecular movement.

    Is there any mention of the length of time(duration) that the spring is kept in the oven?

    At the lower temperature there might be a slow process like osmosis or the fact that glass is actually liquid (if you get my drift).

    It's not soo much about the process either. Sometimes it just what works.

    RJ

    RJ
     
  38. lofty

    lofty Registered User

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    One of the major motor vehicle suspension repairers near me uses a "cold set" method for resetting leaf springs. They do not use any heat at all. I think the springs may be run through a roller system. Perhaps a clock mainspring could be reset by running it through two rollers and therefore have the same effect as hitting it with a hammer along its entire length.

    Lofty
     
  39. shutterbug

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    I don't know. One spring might "recover" better than another. In general, I'll use the old spring if it's not set. Otherwise, I get a new one.
     
  40. hoo-boy

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    That sounds reasonable to me! (another cottage industry potential)
    hoo-boy
     
  41. Richard Barkey

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    This is an interesting thread. Given that I am newer to clock repair I’m not sure I have an opinion but I do have a question or maybe a request for clarification.

    A number of people discussed a spring being “set”. How do you tell if the spring is set and it needs to be replaced or if it is okay to be reused? Is there some guideline to determine this?

    Richard
     
  42. shutterbug

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    It needs to expand to at least 3 times it's coiled size when relaxed.
     
  43. bangster

    bangster Moderator
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    Here's what the original post said:

    bangster
     
  44. Jeremy Woodoff

    Jeremy Woodoff Registered User
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    Here's a variation on this question. I have an Ansonia jumper with a permanently stretched-out coiled spring. I believe these are known as "extension springs": they are normally at rest with their coils together, and resist being pulled apart. Because these are much more compact and made of fine wire, as opposed to the thick metal of a mainspring, it would be relatively easy to heat, cool, and temper the spring. If the spring were tightly coiled and held with clamps, would heating to red heat and quenching in oil restore the spring to its original form, with the coils together when at rest? If so, how would it be determined to what color to temper it?
     
  45. Dave B

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    #45 Dave B, Feb 25, 2010
    Last edited: Feb 25, 2010
    I have occasionally made small compression springs (for shotgun firing pins) by heating to dull red heat, and quenching in boiled linseed oil. The spring is then heated with the oil on it to the point where it self ignites (the flashpoint), and immediatly quenched it again in the same oil. Doing this two or three times usually suffices to give the spring the proper temper. I suppose you could use the same method for a tension or a torsion spring, provided you could get it to heat evenly.

    Here is what Clyde Baker says, in Modern Gunsmithing (Small Arms Technical Publishing Co, Marshalltown, DE., 1928; p. 314):
    "Coil Springs Heat to dull red and dip in linseed oil; flash off oil one, two or three times according to size of spring. Lay aside to cool."

    On page 312 (op.cit.) he says, "A simple and very reliable method of tempering both flat and coil springs has been evolved from the oil tempering process. It is known as "flashing" and consists of first hardening the spring in oil (usually sperm oil), then wiping off the surplus oil and heating the spring again until the small amount of oil remaining flashes and burns off."

    The color for tempering springs should be from deep purple to dark blue (550-601 degrees Farenheit).

    Alternatively, you can harden steel parts in a bath of molten metal. 19 parts lead and 4 parts tin will result in a purple temperature; 50 parts lead and 2 parts tin will result in a deep blue. Lead melts at from 608 to 618, and tin from 442 to 451. All temperatures are Farenheit. By mixing different proportions of the metals, and melting them you can obtain a controlled temperature in which to immerse your workpiece. Proportions are by volume, not weight.
     
  46. hoo-boy

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    Dave, thats close to the method I was tought just a wee tad different
    1- heat to dull red and quench
    2- using a small metal dish(container, jar lid will suffice) cover with regular motor oil(30wt.) with torch set ablaze and let burn off.
    3- Polish and test Always test, test, and test all made springs untill you are sure they will not break! hoo-boy
     
  47. Dave B

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    "Always test, test, and test all made springs untill you are sure they will not break"

    I do that with purchased ones, too. In the case of clock mainsprings, either new ones, or old ones I have cleaned and intend to re-use, I wind them fully and unwind them fully about ten times, before putting them in the clock.

    If the durned thing is gonna break, I want it to do that where it can't wipe out any wheels, arbors, or pinons.
     
  48. bangster

    bangster Moderator
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    Y'know, I find that advice really problematic. If it doesn't break on the first test, then test it again? Right. If it DOES break on the first test, what? Can't test that one again. I can't see any way to "test, test, test" until you're sure it won't break, except by testing it until it breaks, or testing it forever.

    Am I missing something here?

    Someone once asked Don Reno, "How tight should I tighten my banjo head?" Reno is reported to have said, "Tighten it down until it breaks, then back off a little bit."

    bangster
     
  49. Thyme

    Thyme Banned

    Sep 18, 2006
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    Yep. It's called a trial period : testing over a reasonable amount of time. Let it run for about a month or so. Tain't "forever" but it isn't 'send it out the door after the first trial run and hope for the best', either - is it?

    I dunno whether you like my answer. Maybe, maybe not. Maybe it might help you. Maybe not.

    You decide.:)
     
  50. bangster

    bangster Moderator
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    #50 bangster, Feb 26, 2010
    Last edited: Feb 26, 2010
    Sure, I understand. Except I don't think of a trial period as a test. Testing is what you do before you start the trial period.

    What's problematic here is the nature of what we're testing: a hardening & tempering procedure with a given spring (Jeremy's jumper spring).

    Heat it, quench it, temper it with the flame-off. Test it, and it breaks. What then? Can't test that one no mo'. And you've lost the purpose of the exercise, which was to restore that spring.

    The recommendation to "test and test and test" presupposed that you've got a bunch of springs, which you'll process one-by-one until you get one that doesn't break right off. If you're lucky, that will be the first one. And after you've got one that doesn't break right off, you keep testing it until either it breaks too, or you're satisfied it's not going to. But you're not testing the same spring over and over until it (finally) fails to break; you're potentially testing a succession of springs looking for one that doesn't break...right off.

    Maybe that makes my point a little clearer? :confused:

    bangster
     

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