After polishing Pivots

Discussion in 'Clock Repair' started by TEACLOCKS, Oct 1, 2018.

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  1. TEACLOCKS

    TEACLOCKS Registered User
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    After polishing the pivots I clean them with Lighter fluid.
    so I bought the one on the Left to save money, do you think they are both the same :???:?

    DSCF5040.JPG
     
  2. MARK A. BUTTERWORTH

    MARK A. BUTTERWORTH Registered User
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    The naphtha will be as good or better than lighter fluid. It is pretty close to being the same.
     
  3. kinsler33

    kinsler33 Registered User

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    I would think that if the pivots are brightly polished they wouldn't need to be cleaned with anything. Are you concerned that abrasive might somehow be trapped on the shiny surfaces?

    I always give a pivot a final cleaning with a 6/0 crocus buff (the 75-cent variety from Timesavers) which typically yields an overly-dramatic gleam.

    M Kinsler
     
  4. R&A

    R&A Registered User

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    Use pith wood
     
  5. shutterbug

    shutterbug Moderator
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    I think Coleman gas is Naptha, isn't it?
     
  6. Willie X

    Willie X Registered User

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    Yep, with about 1% machine oil to help prevent rust and corrosion on the pump parts. Willie X
     
  7. Bruce Alexander

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    I've just gotten in the habit of running two cleaning cycles. One right after disassembly, and one immediately before reassembly. If you are manually cleaning your movements, I can see where the use of some solvent could be helpful in assuring that the pivot surfaces are free of contamination. I suppose your cleaning agent should be chosen with whatever you're using to service your pivots in mind. For example, if you're polishing the steel with wax bound Rouge, you'll want to use something that can quickly dissolve wax.
     
  8. shimmystep

    shimmystep Registered User

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    Pure acetone on cotton bud sticks for me. I use this to clean off when polishing and burnishing, takes away all the crud and burnishing oil so you can see what you got.
     
  9. claussclocks

    claussclocks Registered User
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    VM&P Naptha, full name is varnish makers and painters naptha, and lighter fluid are both petroleum aliphatic solvents. VM&P will dry faster but both are functionally equal for what you are doing.
    I use acetone because it is an excellent cleaner and dries fast when I need to wipe down a metal part. Acetone will play havoc on varnishes and plastics but a short exposure of VM&P will usually not present a problem. On steel pivots and brass any one of these will work as a quick wipe down.
     
  10. Bruce Alexander

    Bruce Alexander Registered User
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    Just out of curiosity, what are you folks polishing your pivots with? Also, do you burnish them afterwards?
    I polish with Simichrome on a popsicle stick and burnish afterwards. I don't use anything particularly aggressive or volatile in process. A clean section of wood usually followed by just a little citrus based degreaser on a paper towel seems to get the job done well for me. A final clock cleaner ultrasonic bath as previously mentioned to get anything left behind.
     
  11. kinsler33

    kinsler33 Registered User

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    I've had good luck with Timesavers' "emery' buffs, of which all but 1/0, 1, 2, and 3 are fine crocus paper of one grade or another glued to a wood paddle. If I find a barrel-shaped or hourglass-shaped pivot I'll use a pivot file, but for most pivots I start with 1/0 emery and progress to 2/0, which turns the matte finish left by the 1/0 into a respectable polish, then 3/0, which followed by a stroke with 4/0 leaves a shiny finish. Finally a stroke or two with the 5/0 finishes the polish--except that a finishing touch with the 6/0 makes the pivots into jewelry. I've found that for pivots that can't be chucked into the half-inch Jacobs chuck I use in my bogus lathe I can do an adequate polishing job by holding the pivot between a pair of buffs and spinning it with my fingers.

    I've never had much luck with burnishing. For chrome-plated pivots I'll use a new 1/0 buff to strip off the chrome and then just continue as before.

    M Kinsler

    and when the buff wears out it gets added to the pile of clock tilting shims, though after several years I think I may plan a log cabin.
     
  12. John P

    John P Registered User
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    I polish with buff sticks first, then use a burnishing tool with a couple of drops of automatic transmission oil applied.
    Then after all bushing work is done the wheels go back into the ultrasonic cleaner for the second time.
    The plates get washed in the sink and dried with the wheels, then assembly.

    johnp
     
  13. R. Croswell

    R. Croswell Registered User

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    Unless the movement is so filthy as to require pre-cleaning, I usually do the pivot work and polish with 2500 wet or dry followed by Semichrome on wood stick. I wipe the finished pivot with acetone on a paper towel or Kleenex, When I'm satisfied with the pivot and bushing work I wash each part with "Super Clean" (the purple degreaser from Wal-Mart) using a tooth brush, rinse with water and into the US with Deox-007 or Historic Timekeepers for final cleaning.

    RC
     
  14. shimmystep

    shimmystep Registered User

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    First I dye the pivot with a blue sharpie. Then file any wear until no blue is evident with a fine pivot file, this means it is flat with no ruts. I then use 1000/1500 grit to put a better surface on the pivots. Buff sticks turn out to be not economical, I use a stiff feeler gauge blade with the slightly round edge ground perfectly flat. Now you can hold any grit on the blade and apply to the pivot, right up to the edge of the shoulder. The blade will also give you a flatter backing to the paper and a better finish.
    I then burnish from a finish from the 1000-1500grit paper. This gives, in my experience, material to burnish properly to get a 'black' finish. Where it is shiny, that is telling you that you are getting light reflected from tiny imperfections in the surface, shiny is not so good as 'black'.
     
  15. R. Croswell

    R. Croswell Registered User

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    I agree completely! I was answering the original question "After Polishing.....". I like the idea of blue dying the pivot before using a file - I'll try that. Sometimes I just take a light cut with the lathe but a pivot file works well if the pivot is still round and centered. Not so good if there are flat spots. After filing/turning I begin with 1000 grit then finish with 2500 grit backed as you do, or just pinched between the fingers if it only needs a light "touchup" to get that "black ice" look.

    RC
     
  16. shimmystep

    shimmystep Registered User

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    Dying the pivot was a bit of an epiphany for me! Blue sharpies are perfect for it. I work on pivots under a stereo microscope, so you can really see any blue in the imperfections.
    SM.jpg
    You'll struggle to get a black finish from any paper RC, you'll always have fine lines around the circumference with paper, whatever the grit, and you won't get the hardened burnished finish.
     
  17. bangster

    bangster Moderator
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    A while back, Doc Fields posted his recipe for make-your-own buff sticks cheap. Get a bundle of craft sticks (popsicle sticks) from the craft store.Take a sheet of crocus paper (or whatever); spray the back of it with spray-on adhesives. Lay popsicle sticks in rows on it. When the glue is dry, cut them apart. :coolsign:
     
  18. shimmystep

    shimmystep Registered User

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    it is a great tip bang, I did this myself for a while and made them in large batches. I experimented with the glues, and found that wood glue was the best for that. It could be laid thin, and when the paper was applied could be rolled very flat, it also dries real hard. Since though, I've found using a feeler gauge blade with a small slip of wet and dry held against as good, if not better, without all the prep.
     
  19. R. Croswell

    R. Croswell Registered User

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    Done that and it works ok but....... most of the craft/popsicle sticks I fine around here usually do not have square edges and may not apply pressure all the way to the root of the pivot.

    RC
     
  20. R. Croswell

    R. Croswell Registered User

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    I find it helps to keep the paper moving and follow with using the back side of the paper, followed with abrasive polishing compound. I would not rely on paper along.

    RC
     
  21. shimmystep

    shimmystep Registered User

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    Do you burnish RC? I'm interested to know, I do burnish all pivots, but have found that different burnishers give different results on different clocks, so have a variation of them. Some I've made, others bought. I think it's about the the relative hardness of the burnisher steel and the pivot,for example the burnishers I use on French pivots I made, because purchased ones didn't do the best job. The burnishers I made are very well hardened by quenching, though only a little tempered so are actually quite brittle. I'd be interested to know your thoughts.

    Has anyone used a sapphire burnisher? They are very expensive, was always curious about their effectiveness?
     
  22. R. Croswell

    R. Croswell Registered User

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    I've never been able to get the result I expected with burnishing but have only tried commercial steel burnisher. Most of the clocks I see have soft steel pivots which I suspect were never burnished. I've always been skeptical tI what degree burnishing may harden such material, and to what depth. No question that burnishing can produce a smooth surface in the right hands.

    RC
     
  23. shutterbug

    shutterbug Moderator
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    I believe burnishing is less about hardening the surface than it is about flattening out the high and/or rough spots.
     
  24. shimmystep

    shimmystep Registered User

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    It is probably less about about hardening than flattening; the process does compress stress the steel and leave it harder though, and improve the wearing capability of the pivot.
     
  25. R. Croswell

    R. Croswell Registered User

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    It has been demonstrate through the use of electron microscope images (which have been posted here previously) that burnishing and abrasive polishing can both produce essentially the same surface finish. Of course when poorly executed either method will produce unacceptable results. Unfortunately surface hardening cannot be "seen" and is impractical to verify in the clock shop. So how does one know if burnishing really does harden clock pivots? There are usually two answers; the first being some variation of its true because that's what I have always heard, or some "expert" says its so, or that's what I've been taught, or that's what it says is this or that clock repair book by someone who seems to speak as an authority. The second explanation will usually reference known metallurgical and machine shop principals relating to heat and pressure and molecular rearrangement and the like and the assumption that such principals, and the conditions necessary for them to occur, can actually be created when burnishing a pivot.

    This question has come up several times in the past and one of our regular posters (just now I don't recall who it was) questioned whether one burnishing a mild steel pivot could actually create sufficient pressure and heat for any significant hardening to take place without bending or breaking the pivot. I don't know the answer to that and I don't know how prove it but that concern seems valid to me. It would seem to follow that burnishing with insufficient pressure would only smooth the surface and leave one with the false sense that the pivot had been hardened and smoothed.

    So the real question isn't so much whether burnishing can theoretically result in surface hardening, but how can one know whether that objective has actually been accomplished after one's attempt to burnish a pivot?

    RC
     
  26. bangster

    bangster Moderator
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    Bite it and see whether it feels hardened.:rolleyes:
     
  27. R. Croswell

    R. Croswell Registered User

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    Yeah, it was hard before and after but didn't taste very good.

    RC
     
  28. shimmystep

    shimmystep Registered User

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    It is indeed sometimes hard to tell the difference visually, though burnishing does produce a finish that meets better the performance requirements of a steel clock pivot.

    There's no question that burnishing does harden the surface, it's not a theory. And its not about heat, this is cold working. You talk about sound metallurgic theory as if it is witchcraft! Plastic deformation is a thing :)
    The steel will only begin to burnish when the pressure that you apply goes past the point of the steels yield strength, if you have applied enough pressure to change the surface permanently and you have compressed the peaks into the troughs, and visually improved the surface area, you will already have made some difference to the surface hardness.

    How do you know if you have accomplished surface hardening? By burnishing.

    Here's a helpful article for anyone that hasn't burnished but would like to try.

    http://www.nawcc-index.net/Articles/LaBounty-Burnishing.pdf
     
  29. kinsler33

    kinsler33 Registered User

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    Industrial literature doesn't seem to discuss burnishing as a means of hardening metal, but maybe it does. Here's some of what we do know about work-hardening:
    Work hardening - Wikipedia

    It might be worth looking at superfinishing: Superfinishing - Wikipedia

    Note that superfinishing does not leave a mirror finish. But it certainly works well on steel.

    So, go figure.

    M Kinsler
     
  30. TEACLOCKS

    TEACLOCKS Registered User
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    I burnish only after I have had to do any filing.
    Then Clean with Lighter fluid.
     
  31. rgmt79

    rgmt79 Registered User
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    I know that this has been said before on here (Jerry Kieffer I think) but if we are talking about brass movements and steel pivots, then making the pivot harder by burnishing does not improve the wear life of the pivot because the brass will always be softer. In practical terms it may be that a burnished pivot is more resistant to any debris that may find it's way into the pivot hole, but in my opinion it's more important to burnish the brass pivot hole. Of course the pivot should be smooth and polished, but there are other ways of achieving that other than burnishing.

    This also begs the question as to why some clock makers, typically French I think, harden their pivots? and why supply houses try to sell you blue pivot wire for re-pivoting?

    Richard
     
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  32. shimmystep

    shimmystep Registered User

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    Burnishing/hardening the pivot will improve the wear life of the pivot, over one that is not burnished. As you say in your post, it makes it more resistant to wear to any debris that may find it's way into the pivot hole.

    That french pivots rarely need re-pivoting probably answers your question as to why they make them so hard. I see a lot of french movements and the re-pivoting work I do on French movements is mainly from calls I get from someone who has broken one off when working on it.

    Blue pivot wire is very good material for re-pivoting, though other materials including piano also do a good job, also old drill bits etc etc...as long a they are hardened.
     
  33. gmorse

    gmorse Registered User
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    Hi Richard,

    Two questions, so two answers:

    Hardened steel will take a much better polish than when unhardened. Also, it's frequently seen that a steel pivot running in a brass plate has worn far more than the brass; it's counter-intuitive but probably due to the dust and debris of the environment becoming embedded in the brass and taking its toll on the pivot. French movements seem to be extremely resilient and capable of enduring for long periods without adequate lubrication.

    Blue pivot wire is better suited to turning than annealed steel, especially for fine pivots. It's stiffer and tougher and less likely to distort under the cutting pressures. If you're turning a balance staff, starting with blue steel rather than annealed will result in an easier task and a better finish. However, this does pre-suppose that the said pivot steel is decent quality, which isn't necessarily the case these days!

    Regards,

    Graham
     
  34. kinsler33

    kinsler33 Registered User

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    So unless I'm missing something, the clock-pivot problem comes down to this: given what engineers would call an un-sealed, non-precision, steel-on-brass, plain bearing running at room temperature at extremely low speed with light loading, we wish to simultaneously minimize friction and wear over a 100-year lifetime. The variables are: selection of the surface finish, selection of lubricant, determination of the initial fit in terms of both side play and end play, and selection of materials (e.g., brass vs bronze bushings and blue steel pivot wire vs. whatever else there is.)

    One major obstacle is the 100-year lifespan, which is kind of arbitrary on my part given that there's a 200-year-old long-case movement ticking away next to me with its original pivots and holes. If a bearing is expected to have a longer lifetime than we are, then records must be kept of its performance, and they never are, for ordinary, non-industrial/non-astronomical clocks didn't come with a maintenance log. Aside from the materials, we cannot know what the other parameters were when the clock was built except that even new clock bearings always rattled a lot. Even the very concept of 'lifetime' isn't defined with any accuracy: is a hole worn out when the gear teeth can no longer transmit power, or when the side-play equals 1/3 of the pivot diameter, or when the oil sloshes around, or when it just looks suspicious?

    We actually do know a good deal, mostly through the observation of failed movements. Steel pivots running in steel holes tend to be a disaster, for example. Oils fail because they turn to gum over time. Steel pinions and brass wheels seem to last forever if there's no oil present.

    The remainder of our lore seems to have been borrowed from other technologies which may or may not be relevant. For example, automobile engines use plain bearings, but these run at high speeds and high intermittent loads and are pressure-lubricated with filtered oil. Electric meters run with light loads over long periods, but these are sealed and are either jeweled or use magnetic suspension.

    It doesn't help, either, that clock repair doesn't typically include measurements of friction loss, bearing clearances, and the like.

    But still, we're usually able to get our clocks working again even if we leave future generations to guess precisely what we did.

    M Kinsler

    I wonder if any Victorian repair people ever tried to leave instructions or messages in Latin or something.
     
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  35. R. Croswell

    R. Croswell Registered User

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    I believe there is one other important factor and that is the "power" or loading of the pivot. Many spring powered American clocks seem to be grossly over powered and have relatively thin brass plates. It is rather common to find badly worn great wheels in American spring powered (over powered) clocks. There actually seems to be some loss of metal but also some displacement of metal, the end result being a pretty used up wheel. The lesser loaded wheels seldom show significant wear so this is probably more a case of the great wheels being "under engineered" for the loads encountered than the selection of material.

    ".....if there's no oil present" is an interesting thought. For every assumed rule there always seem to be some cases that defy the rules. Some of the nastiest movements that I've seen, dripping with oil and evidence of prolonged over oiling have had some of the least amount of wear to lantern pinions. I believe its the absence or presence of dirt that makes the difference. Oil doesn't cause the problem but we assume, and I believe rightly so, that oil can attract dust and dirt. So how does one explain that so grossly over-oiled movements show minimal wear? Perhaps the excess oil helps prevent abrasive particles from embedding in the metal, or perhaps all that oil all over everything simply attracts a lot of the dust to places other than wear points- places where it may look nasty but do no harm?

    Another related topic that hasn't been mentioned is when we encounter a badly worn pivot or pivot hole, when did the majority of that wear actually occur? I would speculate that it is not a linear process but likely accelerates exponentially when one or the other or both surface finishes become compromised. Then the resulting wear causes misalignment that causes more friction and wear, all of which cascades to the end result of a bearing failure and stopped clock. The takeaway I believe is that the repair needs to be a perfect as possible - as close to original fit and finish as possible (or perhaps better in some cases) or the movement will be returned to service already on its way to a premature failure of the repair.

    RC
     
  36. bangster

    bangster Moderator
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    RC has referenced THIS ARTICLE which is linked in Items of Ongoing Interest, top of the forum.
     
  37. kinsler33

    kinsler33 Registered User

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    It would be nice to know what the original fit and finish was on these mass-produced clocks, but we don't. Some manufacturers left a nice threaded pattern on the pivots and some did not. It's never been clear how the holes were made or finished, and the factory side-play specifications, if any, are likely variable and probably lost anyway.

    Yes, the great wheels tend to look pretty horrible, but in the rest of most clocks the bearing and tooth loads are relatively small. The smallest loads are in the upper train, but that's where the speeds are greatest.

    It's also worth noting that badly worn holes often have smooth pivots riding in them.

    I think my point here is that there are far too many variables involved in clock restoration to apply any sort of industry standards to the work. Brass and steel alloys vary wildly, atmospheric pollutants probably had a major effect (most everyone had a coal stove and gas lighting,) and the formulas used in clock oil were all secret.

    Ergo, it's probably best to be humble and respectful of the work standards of others, for there's no way to tell what our own repairs are going to look like in 98 years.
    (I personally wonder about our push-in bushings.)

    Mark Kinsler

    they'll all be rolling around in the bottom of the case
     
  38. Bruce Alexander

    Bruce Alexander Registered User
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    I like to augment retention with LocTite 680 but that's not typical. I find that press fits can vary in tightness, but even if I didn't use LocTite I kind of doubt that these types of bushings will be rolling around in the bottom of the case 100 years from now. Before bushings were pre-manufactured, they were custom turned. I think the practice has probably been around for a very long time.
     
  39. kinsler33

    kinsler33 Registered User

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    But the old bushings were riveted in place, a practice that I still use on occasion, and that everyone used prior to the introduction of the press-fit kind. I think KWM had the first, and they were generally reviled in the shop I worked in. Later on, when I wasn't fixing clocks, they must have gotten the bushing tolerances right--though often enough they're still questionable--and they came into general use, along with their buddies Bergeon.

    Mark Kinsler
     
  40. shimmystep

    shimmystep Registered User

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    Thanks for finding that Bang, I was looking for it.

    They are great pics, and show the positive outcomes that burnishing can bring in terms of bearing surface quality.
     
  41. Bruce Alexander

    Bruce Alexander Registered User
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    What do you mean "riveted in place"? Are you saying that no one installed press fit bushings prior to the KWM system?
     
  42. bangster

    bangster Moderator
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    I think he means they weren't JUST pressed in; they were given the ball-bearing treatment to lock them in place. Right?
     
  43. MARK A. BUTTERWORTH

    MARK A. BUTTERWORTH Registered User
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    Right. My personal belief is that the invention of the pressfit bushing system is one of the great inventions in terms of efficiency for clock repair.
     
  44. Bruce Alexander

    Bruce Alexander Registered User
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    #44 Bruce Alexander, Oct 6, 2018
    Last edited: Oct 6, 2018
    Well, that can still be done with press fittings. Personally, when I custom turn a bushing, it's a pretty tight fit or I don't use it. Perhaps that's just the way I was taught since there have always been pre-fabricated press fit bushings for the short time I've been working with clocks.

    Okay bangster and Mark. Thanks. I still think that the principle is still the same whether the new brass is deformed into a friction fit after or during placement.
     
  45. shimmystep

    shimmystep Registered User

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    Poor tolerances of bushings have been mentioned above, though it is the user that creates the tolerances. You don't have to use the whole of the reamer to make the hole in the plate for the bushing, KWM, Bergeon or hand held reamers. If when fitting the bushing it feels as though it has gone in too easily, it needs to be re-done.
    We've all done it though, cut that little bit too much out of the new hole for the bushing. If you don't want to make a bigger hole for the next size up, place the bushing centrically between the jaws of a vice and give it a little squeeze, doesn't need much. It'll then give you a much better fit. You will need to re-cut the pivot hole once fitted.

    A well fitted press fit bushing is not going to be found rolling around the clock case floor in a hundred years.
     
  46. Bruce Alexander

    Bruce Alexander Registered User
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    You're supposed to just "break through" to the parallel sides in the KWM System.

    I think that depends on your definition of "too easily". If the bushing just falls through, you've probably used the wrong size reamer, kick yourself before you do anything else just to make sure you're now paying attention. If the bushing stays but you're uneasy about how well it will stay, you can tighten it by staking (or riveting) it to the plate followed by broaching to the necessary I.D.

    I usually finish seating my bushings this way but with a craft or popsicle stick on the exterior surface. I find that it quickly gives a very nice, flush fit on the inside surface of the plate which can be critical for end-shake. Sometimes riveted lever posts or other plate components can be difficult to work around but there's usually a clear path for the jaws of the vise assuming that you're not trying to use a monster.

    I think that you're right here. If you're bushing great wheels, however, you want to make sure that the bushings can't be pushed out by the weight of, or lateral forces generated by the spring. That can lead to a catastrophic failure. A very tight fit is indicated here. In my opinion, you should need a vise to seat these types of bushings. If in doubt, a little touch of solder or LocTite can be a good insurance measure. You just don't want to let a wound-up mainspring go buzz-sawing around inside of your movement. Don't ask how I know. :eek:
    You've been warned. :emoji_skull:
     
  47. shimmystep

    shimmystep Registered User

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    I regularly re-bush main wheel bearings, including English longcase clocks which may have 12lb weights, well aware of the possible consequences! These not only require tight fitting with a vice, but require peening into a chamfer, as below.

    These bushing I made tapered, from brass rod that a friend and I foundried and made from scrap English longcase movement plates. This means that the bushings meet the colour of the brass of the time.

    Completed bushings made.jpg
    Peened bushes.jpg
    Bushed main wheel pivots front.jpg
     
  48. Bruce Alexander

    Bruce Alexander Registered User
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    I wouldn't say that I bush great wheels regularly, but I do not hesitate to bush them if I think it's necessary.
    What tool do you use to peen? Do you peen into a chamfer?

    Please tell us more about the Foundry. Is it a back yard type, or do you and your friend regularly work with molten metal? I understand that not burning off the zinc while melting brass can be a little tricky. As always, it's "more than a notion" as dear old relative used to say.
     
  49. shimmystep

    shimmystep Registered User

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    yep, peened into a chamfer, which you can just see around the edge of the hole.
    Inserted bush.jpg


    The foundry is essentially an old barrel, that has a bottom and sides built up with perlite/furnace cement mix, with a propane burner and blower, It's home made, the second one we've made. The first one failed due to developing large cracks in the cement. Our fault, we didn't do a very good job at conditioning the furness to get up to temp, plus the ratio was probably a little too much perlite bias. We use moulding sand for rods that are 12cm long, and two different diameters. One for back plate main wheel bushings and larger for front plate bushings. They need machining from the rough to useful rods with a finish, which we do in a lathe between centres and a dog carrier. It is very satisfying.
     
  50. Bruce Alexander

    Bruce Alexander Registered User
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    I can imagine. I've done a little reading on the subject. Don't know if I'll ever get around to it without burning the garage down. Very nice job Shimmy, as usual. :thumb:
     

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