Rapid bushing wear

Discussion in 'Clock Repair' started by hickorydickorydoc, Oct 4, 2019.

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  1. hickorydickorydoc

    hickorydickorydoc Registered User

    May 25, 2007
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    Hello,
    Eight months ago I overhauled a T&S movement from a Waterbury schoolhouse-style wall clock. It had a broken strike mainspring, which I measured at 3/4" x 0.0155" x 108".
    I replaced the mainsprings with new ones of 3/4 x 0.016 x 108". I replaced 9 bearings with Bergeon brass bushings, polished and burnished pivots, pallets, etc. and everything seemed fine for a test period.
    Well, here it is in the shop again - the 'new' front T2 bushing is shredded with big brass filings stuck in the blackened oil, and an egg-shaped hole. The other bushings appear OK, but the oil is generally darkened.

    Do you think this was a 'bad' or soft bushing? Or did I overpower the clock with the new springs?
    I am wondering whether to put in bronze bushings for the second wheel pivots, or to switch to 0.014" mainsprings. Or both...

    Thank you for any advice!
     
  2. Willie X

    Willie X Registered User

    Feb 9, 2008
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    That main-spring should be fine. It's not the problem. When this happens, the culprit is nearly always the pivot. Check it with a microscope. I think you will see an obvious problem. Another thing that can do this is abrasive particle/s somehow got into the pivot hole. Doesn't take much, just a tiny speck of anything harder than brass.

    Could you make an extreme closeup photo of the pivot in question?

    Willie X
     
  3. hickorydickorydoc

    hickorydickorydoc Registered User

    May 25, 2007
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    Thank you for the quick reply! After bushing, I always go through with a smooth broach, and then do a final wash in the ultrasonic, then rinse and dry, but it's so hard to rule out the possibility that some grit fell in there during assembly and manipulation. Just haven't had this type of quick deterioration before.

    Here is a photo, as close-up as my 'super macro' setting on the camera will go. I can't see any defects with my loupe, but I did check under a 30x microscope - there might be a hairline crack straight along the length of the pivot on one side, involving the middle 2/3 of the length. But I certainly couldn't feel any ridge or crack with a graver edge or an X-acto blade.
    Maybe worth re-pivoting??
    Thanks again!
    469205-ce04ca260ad9679ba3d4a854d071c539.jpg
     

    Attached Files:

  4. R. Croswell

    R. Croswell Registered User

    Apr 4, 2006
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    I believe the first stop is to confirm whether there is or is not a "hairline crack straight along the length of the pivot". If there is, then I would re-pivot. You said in post #1 that you "polished and burnished pivots", which? Either way the pivot should be mirror bright with a kind of black ice look. Did you use a tapered broach to enlarge the opening in your Bergeon bushing? Personally I would not use a tapered smoothing broach in a new bushing with a straight (non-tapered bore). I would use a tapered smoothing broach in a bushing that has been opened with a tapered cutting broach. Use oil of the type that will be used to oil the clock on the tapered smooth broach and peg the hole after broaching and ultrasonic cleaning. If possible select a bushing that does not need to be broached. This bushing is under heavy load and if the hole is tapered, even tapered from each end, the initial contact area between the pivot and bushing will be tiny. That could encourage erosion at that point and the resulting debris would erode the rest of the bushing at an exponential rate. Are you sure that you oiled that pivot? It's a large pivot, use as much oil as will disappear in the bushing.

    My recommendation (unless the pivot is actually cracked) based on the fact that you have never had this problem before or with the other pivots in this movement, is to repolish or reburnish the pivot and inspect under a microscope, replace the bushing, be sure to oil it well and see.... That movement didn't originally have bronze bushings and bronze should not be necessary but is an option if you like. I do not believe the Bergeon bushing was "soft" or defective, but something may have become embedded in it during the broaching process. I agree with Willie, your spring selection is not the problem.

    RC
     
  5. Willie X

    Willie X Registered User

    Feb 9, 2008
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    I think RC covered everything.

    You do have fine score marks across the whole surface of the pivot. This is left from your fileing and/or burnishing operation but should have come out with your polishing operation? A fine buff stick will usually remove those. Use 800 to 1000 wet and dry 3M auto paper. Then polish on a muslin wheel with Tripoli or a hard leather buff charged with tripoli.

    Normally, the pivot you show would wear in and be fine. So, I would lean toward the no oil, cracked pivot, or a hard pivot that was not polished well enough. It started to wear out before it wore in.

    "Wear begets wear". This applies to all machinery and I heard the saying long ago from one of my famous uncles.

    Willie X
     
  6. Bruce Alexander

    Bruce Alexander Registered User
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    Feb 22, 2010
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    First, let me stress that I agree with everything that has been said. Something is different about this bearing. You don't stipulate where the other eight bushings you placed are located. You also note that the oil is noticeably darkened. What oil are you using and what do you attribute the darkening to? Is it just age/oxidation or is something suspended in it? Was there any trace of oil in the worn bearing or was it dry?

    As long as you have the movement apart I would carefully double-check all of the pivots.

    I hope folks don't mind if I chime in here regarding the mainsprings. New Steel can be expected to generate more torque than an original "antique" steel spring of the exact same dimensions. Also, old springs tended to have rounded edges whereas new spring steel has squared edges and is shaped in rectangular fashion. This can add 5=10% more torque alone*. In going from 0.0155" to 0.016" you potentially increased the torque out of your mainsprings anywhere from 10-20% and that's before any considerations on the differences between old and new steel. Also keep in mind that American Clocks such as these were overpowered to begin with, especially if they were fitted with Recoil Escapements. All this to say that you should be very careful when considering an increase in spring strength. Generally speaking, it's not a good idea.

    Please keep us advised of your progress.

    Good luck,

    Bruce

    *As per Tom Wining page 74 "Clockmakers Newsletter Workshop Series Book 1 Repairs" by Steven G. Conover.
     
  7. R. Croswell

    R. Croswell Registered User

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    Hickory, American clocks similar to your Waterbury schoolhouse clock often used main springs as thick as 0.018" with this type of bearing with no problem. Going from 0.0155" to 0.016" thick springs will not be an issue. The original springs in your Waterbury were likely "modern" spring steel. The so called wrought iron or antique springs I believe were mostly out of production by the time this clock was made. There will initially be a little more torque with a brand new spring before it takes an initial "set" but the effect seems to be relatively short lived, and, unless the original spring was busted, it may have taken a small amount of set over the years and produce slightly less power but hardly ever enough loss to cause a problem. Your problem with this clock is related to the pivot, the bushing, or the oil or lack of same.

    RC
     
  8. Willie X

    Willie X Registered User

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    Another big factor, American clocks just don't wear very much at this point. I rarely replace a bushing on an American second wheel pivot. So, for this pivot to suddenly decide to eat up its bearing surface here would indicate something big is wrong. Might not be easy to see but it's big. Say "big" like Barney Fife says it. Ha

    WIllie X
     
  9. tom427cid

    tom427cid Registered User
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    A few years ago there was quite a discussion on another MB-mostly professionals- regarding Bergeron brand bushes. The concensus was that apparently they (Bergeron) was making bushes that were "soft". I do not want to start a war-us vs. them. But I prefer to use KWM because they are smaller and the finished product looks neater. And it was recommended to me when I started, to use the hard brass bushes. All I can say is "so far so good".
    Anyway just my .02
    tom
     
  10. Bruce Alexander

    Bruce Alexander Registered User
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    Feb 22, 2010
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    I don't think the author I quoted was talking about wrought iron springs RC. As I read it, he specifically stated "Steel".
    "Springs we buy today are, for the most part, the finest springs ever made. The content of the steel is carefully controlled. The hardening and tempering are done at the rolling mills..."
    He goes on to compare steel spring manufacture in the "past" (no date given),
    "before spring steel could be hardened and tempered at the rolling mills. the springs were formed, hardened, and tempered in spring boxes. A strip of unhardened spring steel was put in a bronze box, which had a spiral groove in it. The lid was put on and the box was heated to the hardening temperature. Box and all were then quenched. Then the box was placed in oil and brought to the tempering temperature. Box and all were quenched again. In this old method of making springs, the edges of the spring tended to be harder than the middle...The temperature drop was much slower toward the center of the box, allowing the steel to partly reform as pearlite instead of martensite" *

    Again, I repeat for the record....


    I'm not arguing that Hickory's chosen springs were too strong. For one thing, we don't know what model clock/movement he's working with and even if we did, I don't see original spring specs listed in my references (Tran) for Waterbury movements. As pointed out, the original springs may have already been replaced. We don't know. All I'm stating is something that shouldn't be controversial, namely, be very careful if you're considering a mainspring replacement which is stronger than the one you find in the movement. I think wear patterns will be a big indicator of whether or not the movement is overpowered. This would be evident throughout the gear trains probably starting with the Main Wheel.

    Something else is going on here. The OP needs to identify it and address it or risk having the problem reoccur. Going down to a weaker mainspring, in this case, will probably have no effect and could possibly under-power the movement IF the original mainsprings were indeed the common 0.018" variety.

    I prefer KWM bushings too Tom. I've also read that they may offer an advantage when one needs to bush Steel Plates. The smaller KWM's may fit well inside of the brass plugs forming the original pivot holes. I haven't done this yet myself as I've not seen a steel plate on my bench yet, but it makes sense. Plus, they're just more conservative and "neat". In my opinion. Often fitting inside the original oil sink.

    Regards,

    Bruce.

    *page 73 of previously referenced Conover Text.
     
  11. R. Croswell

    R. Croswell Registered User

    Apr 4, 2006
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    Bruce, the spring chart I have lists 3/4" x .017" x 120" as the time spring for a number of Waterbury models (none over 0.017") models, but we do not know the OP's model. I've found a number of Waterbury kitchen clocks, including 2 of my own that had thinner main springs than many other brands. I used 3/4" x 0.016" x 108" in mine and it is fine. I tried 0.014" thick and it ran but was under powered. I would expect a Waterbury schoolhouse clock to use a similar movement.

    I've used Bergeon bushings for many years with no problem. There are obvious pros and cons between brands and styles. I believe that one of the reasons that 2nd arbor bushings may fail is that many American clocks do not have thin plates and do not have an oil sink at that location. Bergeon bushings have a relatively deep oil sink so if a bushing is selected that has a height equal to the thickness of the plate the actual area of the bushing in contact with the pivot is much less than that of the original plate pivot hole. I always select a bushing taller than the plate thickness for this application and use the Bergeon "pivot cutter" to trim the bushing flush removing the oil sink and restoring the original contact area. In my opinion any advantage of an oil sink is more than offset by the extra bushing area in contact with the pivot. Perhaps this was a factor in the OP's bushing failure as well?

    RC
     
  12. R. Croswell

    R. Croswell Registered User

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    Correction, ..........is that many American clocks have thin plates and do not have an oil sink at that location.......

    Sorry, I can't type
     
  13. hickorydickorydoc

    hickorydickorydoc Registered User

    May 25, 2007
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    I do appreciate all the input here, everyone - thank you! I can try to fill in some gaps or questions that came up in the responses.
    This clock is Waterbury's drop octagon "Yeddo" model with 8" dial. The movement front plate is stamped with a "K" top left, and has 7 1/2 " stamped lower right. It had a broken strike mainspring, and I replaced both springs.
    I clean my new mainsprings before installation, and use Keystone lube. I'm not a fan of stretching mainsprings out straight, BTW.

    The opinions on bushings are interesting! I've been using the Bergeon system for a long time and have not noticed any quality problems. Sometimes the smaller diameter KWM bushings would be nice to use near plate edges and in close quarters. Maybe I should get the KWM reamer set for my Bergeon bushing machine, but the KWM numbering system seems hard to get used to. I like the direct measurements of the Bergeon.
    On this clock I put bushings in the front of T2 and S2, rear of T4, and both ends of T3, S3, and escape wheel.
    If I'm lucky to have a stock bushing about 0.03 or 0.04 mm bigger than the pivot, I don't broach it. But usually I have to open up a stock bushing to the pivot size, using a cutting broach from both sides a little at a time. When it's almost big enough, I switch to a smoothing broach for final fit, but I didn't know these could/should be oiled?

    Can o' worms #1 = oil. For quite a while I have been using Etsynthia 859 for most clocks, and the same company's Silber B for pocket watches, platforms, and small pin pallet balance wheel clocks. I'm careful not to over-oil, and have been told once that I don't use enough! I know I didn't skip this pivot in question, because the brass filings and chips adhered and collected in the oil sink. Many of my own clocks do seem to have darkening of the oil within a year or so, and I have no idea if it's due to something about that particular oil, or something I'm doing wrong...

    Can o' worms #2 = pivot polishing +/or burnishing. Here goes my current procedure: where I start in this sequence depends on how bad the pivot is to begin with... Assuming a badly scored pivot that is salvageable, I'd start with a pivot file, then progress through 400, 800, and 1200 wet/dry paper (wet) glued to flat stock. Then I switch to buff sticks, 2-0 if needed, usually 4-0 and then a long time on 6-0, and finally a leather or chamois buff (but not charged with anything). My understanding is that any polishing effort is removing at least some material, and that burnishing does not remove material, it just smooths over any micro-bumps on the surface. So my last step on pivots is oil on a smooth steel burnisher at high speed, wiped down between pivots. Then back through the ultrasonic.

    So - on RC's suggestions, since the plates are thin and the bushing oil sinks are deep, I used a thicker bushing when I re-did this bad one. That spot gets the direct force of the mainspring and first wheel. Also, I will pay attention to clean handling of the movement until it's back in the case. I'm pretty sure there must have been some contamination or grit that created a grinding paste in the hole.
    Thanks again for all the advice!
     
  14. Willie X

    Willie X Registered User

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    #14 Willie X, Oct 6, 2019
    Last edited: Oct 6, 2019
    Those score marks probably came from your burnisher. I'm pretty sure you're upsetting metal there and leaving a 'shaggy' (file like) surface. 400 paper alone should leave a surface similar in appearance but less abrasive (file like). I would put that burnisher away and go to polishing. You can get good results going from 400, to 800, to tripoli on a muslin wheel, or hard leather buff. The metal removed is negligible and it shouldn't take more than about 10 to 20 seconds per step.
    Willie X
     
  15. kinsler33

    kinsler33 Registered User

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    I vote for a longitudinal crack in the pivot. When the clock is fully wound the second time wheel is under a good deal of stress and any crack in the pivot could open up and form an efficient scraper. I did not believe that a pivot could suffer such a crack until I found one, and even then I didn't quite believe it. Something in the rolling or drawing process with which the original steel rod/wire was formed must be at fault.

    About the only thing you can do would be to re-pivot T2 and then install a new bushing. The pivot work you did originally sounds perfectly adequate, and I cannot imagine that the most un-polished pivot running devoid of oil could produce the degree of damage you've found. Nor can I think of anything you could have done to prevent that damage, for the crack was and presumably still is invisible except when the shaft is under load..

    You'll have to remove the questionable pivot prior to re-pivoting, so it might be worthwhile to carefully cut it off, say with a jeweler's saw, so you can inspect it closely. Depending on the extent of the crack, if any, the pivot might come off in two halves.

    M Kinsler
     
  16. Uhralt

    Uhralt Registered User
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    Before I'd go through the effort of re-pivoting I would take a good look at the pivot under a stereo microscope. It is remarkable what you can see at 20 to 40 times magnification.

    Uhralt
     
  17. Willie X

    Willie X Registered User

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    I'm with Uhralt. This problem, whatever it is, won't be invisable. Willie X
     
  18. shutterbug

    shutterbug Moderator
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    I would lean toward user error. I know I've overlooked a pivot or two when oiling over the years, and that may be what happened here. As Forrest Gump would say "It happens!" :D
     

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