Pivot polisher

Discussion in 'Clock Repair' started by Charles E. Davis, Aug 13, 2005.

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  1. Charles E. Davis

    Charles E. Davis Registered User
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    #1 Charles E. Davis, Aug 13, 2005
    Last edited by a moderator: Sep 8, 2013


    A request from RJ asked about the pivot polisher I make from a hinge. The construction is self explanitory but I will post a latter message giving some sizes of the runners. The whole idea is based on the turns and expects one to have a combination pivot file and burnisher. Rather than using a bow I turn it with the equivalent of a small squeegee blade.

    LLight.jpg Squeegee.jpg
     
  2. Charles E. Davis

    Charles E. Davis Registered User
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    #2 Charles E. Davis, Aug 13, 2005
    Last edited by a moderator: Sep 8, 2013
    A request from RJ asked about the pivot polisher I make from a hinge. The construction is self explanitory but I will post a latter message giving some sizes of the runners. The whole idea is based on the turns and expects one to have a combination pivot file and burnisher. Rather than using a bow I turn it with the equivalent of a small squeegee blade.

    LLight.jpg Squeegee.jpg
     
  3. Charles E. Davis

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  4. Charles E. Davis

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  5. Steve Patton

    Steve Patton Registered User
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    Charlie,
    Simple, efficient, effective and a beauty!
    Oh, did I say inexpensive too.
    Thanks for sharing...Great picture details.

    Steve
     
  6. TomT

    TomT Registered User

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    Charles,

    I think your pivot polisher set up is terrific!!

    The left hand shaft (opposite the pivot support). How is the arbor held in it? Is is just a slip fit?

    http://members.cox.net/tnttemple2/Polisher.jpg

    Thanks
     
  7. eskmill

    eskmill Registered User
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    In Charlie's photo, the left end of the arbor isn't fastended to the left runner. It just seats in a bore in the runner which has been counter bored to receive the pivoted arbor.

    The traditional method involves the use of a small bow with the string wrapped around the arbor being worked. Charlie uses a short piece of rubber squeegee to turn the work to and fro. Downward pressure on the arbor keeps it seated between the runners.

    Not shown in the photos is the use of a pivot file or the burnisher used to "dress" the pivot saddled in the brass runner on the right. Some lubrication is wise and many use kerosene, the "mother's milk" of horology.

    Charlie always has an audience at meetings and Marts demonstrating his pivot polisher and his many other clever tools-of-the-trade that he's constructed.
     
  8. dutch

    dutch Registered User

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    #8 dutch, Aug 14, 2005
    Last edited by a moderator: Sep 8, 2013
    I really like the looks of your pivot polisher and am going to make one but I have never understood why chucking up the arbor in a collet on the left side and supporting the pivot on the right side as shown,but held in the tailstock of a lathe is not recommended.
    I have never been satisfied with my pivot polishing but have never seen anyone else do it and maybe I am expecting too much,and after reading about using a bow to turn the arbor I suspect I have been turning too fast.
    Dutch
     
  9. David Robertson

    David Robertson Registered User

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    Dutch,

    I think many people advocate doing just what you are doing.. It takes the right combination of file and burnisher work and speed variation to get it right, but using your lathe as you have described is a good way to go.
     
  10. Robert Gary

    Robert Gary Member, NAWCC Board of Directors
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    Charlie:

    Thank you for posting the photos. Great idea and design!

    RobertG
     
  11. bangster

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    I take it that the "bushings" in the two ends are pieces of the original hingepin, center-bored to receive the two runners, right?

    And the setscrews go THROUGH the bushings, and bear on the runners, right?

    And what about those dimensions?

    bangster
     
  12. Lloyd Lehn

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    Some folks asked about the dimensions. One of the Huckabee tapes available from AWCI has the details of how to make the pivot holder pieces or runners. Huck uses a lathe instead of a hinge. I made his pivot polishing tools and as recall he uses every number size from N to M in the number drills. I just don't recall what the N and M are but don't think that matters. Everyone will have to pick the sizes that he would most probably use. I used a brass rod and drilled the holes in the end to make a female end. Then I milled the side of the brass off until about 1/4 to a 1/3 of the rod was removed for about 1/4 inch or so. By selecting these home made runners that just fit the pivot size, one assures that you can polish the pivot but at the same time have some assurance that the pivot will not jump out of the hole since it is still somewhat held in.

    It appears in the hinge pivot polisher that the left hand runner is simply a female runner with a place to put the left end of the arbor. If that is not right, please let us know.
     
  13. Charles E. Davis

    Charles E. Davis Registered User
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    Thank you for your good words.
    I first made these pivot polishers when I started a class at a creative workshop at our church during the month of July about 30 years ago. I had been polishing pivots using an old set of turns that I had found at a swap meet. If eight men and women who had bought old Japanese Schoolhouse clocks from me were going to get the movements overhauled in four evening sessions I was going to have to be able to take care of the tooling situation. I borrowed a large ultrasonic from the university I was teaching during the summer session and made up a bunch of these hinge polishers so everyone could do it at the same time.
    I had earlier made my own runners to fit the turns out of a length of brass tubing that was the exact size needed to fit the turns (the same OD as punches of my staking set.) The holes in the hinges needed a bushing so I could continue to use the runners that I had made and also the extra tubing that I had. Rather than use the lathe, and also to encourage the students to make their own, I found a rod that was slightly larger than the pin and used a drill of that OD to drill out the hinge. Then I drilled a hole in the bushing to match the OD or the runners. Yes the thumbscrew goes through the hinge and the bushing and holds the runners in the right position.
    The tubing had the advantage that I didn't have to drill a hole in a solid rod. Instead I reamed out the end with a No. III reamer and soft soldered in various sizes of bushing to support the pivot. If I remember rightly, I used a jeweler saw to form the lip for the pivot. Probably dressed it to size with a flat file. I have never located that tubing since so have been making them from solid brass rod.
    I have never felt comfortable having students use the power with a lathe to polish pivots and personally have found the turns to be more than adequate. Beginners are better off working without power tools. And besides how to you chuck the arbor in the photo to polish the end to the right. Even if you drive it with masking tape you are taking a great risk.
    Like I said, I use the pivot file and burnisher and avoid abrasives. It will be interesting to hear how others handle pivots.
     
  14. doug sinclair

    doug sinclair Registered User

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    Charles,

    How do you go about getting a good final polish on a pivot with the pivot turning in a runner? Considering the runner is likely charged with metal particles from the previous stages of the polishing procedure.
     
  15. Jerry Kieffer

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    Charlie
    This post is in response to your question on how others polish a pivot. it is not intended to conflict with your procedure but only to answer your question. (I think I have stirred the pot enough lately)
    Personally when I work on a pivot I am trying to accomplish three things. First I want a round pivot. Second I want it staight and square. Third I want the highest qaulity surface finish possible in a reasonable amount of time. For myself the most practical method of doing this is with a Lathe. On a worn pivot I will take a very light cut just enough to clean up the worn area. This creates a straight round pivot with out any taper. If the pivot can be held close to the lathe collet it is only supported by the collet. If not one end of the arbor is held in the collet and the other end is held with a steady rest for cutting and polishing. I have not burnished pivots for some 20 years. It has been my experience that a superior surface finish has greater impact on pivot/bushing life that surface hardness providing the pivot is harder than the plate. My polishing metods are also different than traditional methods. I polish starting with 600 grit silicon carbide paper then move to 2000 grit and then to 4000 grit. They are applied to pivot double thickness under a pillar file with light pressure. Since I use 1/4" brazed carbide tools the shank of the tool is shifted out one side of the tool post. The tool post is then turned so the exposed tool shank is parrellel to the pivot. This allows the pillar file to lay on the exposed tool holding it square to the pivot preventing taper in the pivot. This proceedure will produce a mirror finish on a pivot that is straight square and round in a very short time. Many people have told me that I can not use abrasive paper because the grit will embed itself in the pivot. I have never been able to find any evidence of this under an inspection microscope even as high as 100 power. No one claiming this has ever been able to show me an example. Everything is possible and I am sure it has happened but I have never seen it. On the other hand I have seen chips from a burnisher imbeded in a pivot a couple of times over the years under a microscope. I use this method personally because I have never had to resevice any repair where the pivot/bushing were installed Square , round and straight with a supierior finish in the past 20 years. That has not been the case where I have used traditional methods with the skills I had at the time. We each have our own methods and I am a firm believer that the end result is far more importent than how we get there.

    Jerry Kieffer
     
  16. Robert Gary

    Robert Gary Member, NAWCC Board of Directors
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    #16 Robert Gary, Aug 15, 2005
    Last edited by a moderator: Sep 6, 2013

    Jerry:

    Could you please post a photo of this part of the procedure? I am having difficulty visualizing it.

    Thank you.

    RobertG
     
  17. Steve Patton

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    Hey guys,
    Keep on stirrin the pot. This is great stuff! This is what
    we are about. Right? The end result....
    Don't think about being shy. Jump on in and lets sort
    this out. I've only polished a couple of clocks worth and
    definitely crave input. I think I have been overly cautious
    fearing damage. Maybe too light a touch? They looked
    pretty clean under 10x mag. Perhaps I need closer examination?

    Steve
     
  18. Robert Gary

    Robert Gary Member, NAWCC Board of Directors
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    Good point, Steve!

    I can't yet afford a microscope for clock work. Jerry, (and others), what minimum magnification would you recommend for evaluating one's pivot work?

    RobertG
     
  19. Charles E. Davis

    Charles E. Davis Registered User
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    I'm thrilled with the responses. And I am especially pleased that Jerry has entered the conversation. His work and methods have really impressed me as he works to a very high quality.
    As I see his procedure the tool is used much like a filing guide to maintain the parallel pivot.
    Great idea. Maybe I need to add it to the hinge?
     
  20. Jerry Kieffer

    Jerry Kieffer Registered User
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    Robert
    I don`t have a Digital camera like I should have. The standard tool post on my Sherline Lathe (A well as Taig,Unimat and others) holds the lathe tool Horizontal to the cross slide table. Therefor anything sticking out the side of the tool post that is parellel to the work piece will allow you to lay the file on it. This will hold the surface of of the file parallel to pivot that was just cut straight square and round to prevent taper.

    Robert and Steve
    I see no need for a Microscope in clock work unless it is used on equipment for a vision problem. I only mentioned this to show how I was able to verify the results of my procedures.
    I see no reason for more than a 3x and 5x Qaulity (At least Glass) loupe for normal clock work inspection. I just completed an article entitled " Optics for Micro Machining" that will be appearing in a upcoming issue of the "Home shop Machinist" . Not sure when but it is sold in the larger chain book stores. It covers all aspects of Optics through the use of stereo Microscopes on machine tools. The only reason I mention this it took six pages of text and twenty photo`s to answer a simple question. Far more than wish to type out here but a way for someone to get the info if they wish. It is of course based on my opinion and no better than whatI can personally demonstrate.

    Jerry Kieffer
     
  21. Robert Gary

    Robert Gary Member, NAWCC Board of Directors
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    Jerry:

    Thank you. I need to up-grade my optics, so this will help immensely.

    RobertG
     
  22. Jerry Kieffer

    Jerry Kieffer Registered User
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    Charlie
    Thank you for the kind words, However I have feeling that your personality and methods has attracted more people to this hobby than I have. I would like to make a suggestion if I could. If you were to machine your runners from drill rod and harden them the front lip could be elevated slightly and act as a guide.
    I think this may address some of Dougs concern since they would not load up as easily.

    Just a Thought

    Jerry Kieffer
     
  23. TomT

    TomT Registered User

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    As a note, there is an excellent little hand held microscope available from (oddly enough) Radio Shack. It is focusable and is lighted.

    MicroScope

    It does a very nice job of showing what's going on up close. The PN is 63-113 and it's only $10.

    Regards
     
  24. Steve Patton

    Steve Patton Registered User
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    Tom,
    Thanks for the Radio Shack solution!
    On my good days I'm just half blind.
    This will be a multi-purpose tool.

    Steve
     
  25. RJSoftware

    RJSoftware Registered User

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    Hey Charlie;

    Wasnt me who asked about the pivot polisher. Another guy stepped in the conversation.

    Now I can ask.

    Why bother polishing the pivots? Or maybe a better question is- What movements are so sensitive that they would require that much attention to detail?

    RJ
     
  26. eskmill

    eskmill Registered User
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    Dear RJ. Clock and watch arbor pivots are polished not just for appearance, but instead to "work harden" the surface of the metal. Some repairers insist on grinding the pivot to a mirror finish with abrasives but traditionally, the burnisher is used to provide a smooth and hardened surface to the pivot.

    It's the same for any bearing journal whether it's for the balance staff on a fine watch or the journals on your car's crankshaft engine.

    Except in very rare situations, the pivots must be cylindrical, smooth and harder than the hole they turn in no matter whether it's for a covered wagon wheel or a watch.

    Finally, the answer to your question: all of them. It's the simplest thing you can do for a clock to give it a new life.
     
  27. Steve Patton

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    RJ,
    The other guy has a name (RobertG), and he didn't step in the conversation!
    He joined a discussion. Just as you joined this one. Hope you can understand the difference.
    There are no exclusions here. This is an open forum. Everyone is welcomed and encouraged
    to participate. One discussion can lead to multiple others. This is the nature of the board.
    No glory in who asked the question, but that the question was asked.

    Thanks to all participants in this thread. I once more come away with added insight
    and knowledge. A never ending quest, I might add.

    Steve
     
  28. RJSoftware

    RJSoftware Registered User

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    I did not say he stomped or bothered my conversation. I say he "stepped in".

    I guess things like my intention and meaning can be mis-interpreted. In general "stepped on" the conversation means to interrupt. "stepped in" means joined.

    But I understand what you mean. Kinda like a guy who starts criticizing a newbie for when he is persistant in getting the right answer.

    Sure takes patients right? ;)

    Just like you say it's just conversation.

    It's not like it's some kinda teeny bopper chat room where miss popularity decides who's cool and who is not.

    You know how control freaks are...

    What I say is this. Don't worry. Be happy!

    Me, I am never overly serious about anything.

    Btw, I hear/tell the guy who wrote that song comitted suicide.

    Odd hey...
    RJ
     
  29. Robert Gary

    Robert Gary Member, NAWCC Board of Directors
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    I wasn't offended. I stepped into the conversation the way one steps into a conversation around a mart table at the local chapter meeting; everyone welcome, no one excluded.

    I think "RG" has been mistaken for "RJ" on a couple of other posts as well. (RJ: Do we look alike or something?). LOL

    RJ, when you have torn down a few dozen clocks, you will see that a lot of them, if not most, have pivots that are badly scored. Dressing them up, polishing, and hardening them is essential to eliminate power loss throughout the train.

    RobertG
     
  30. Charles E. Davis

    Charles E. Davis Registered User
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    Again I want to thank all of you who have contributed to this discussion about ways to use the tool I pictured.
    I started using it based on what was described in the books and magazines that I had read at that time. It seemed to work so I have stuck with it. And it did seem so much better than using a pin vise and a notch in a piece of hardwood to dress and burnish the pivot.
    Until Jerry mentioned the use of ultra fine silicon carbide (4000) cloth in double thickness backed by a burnisher, I had always thought in terms of red stuff and diamantine on a bell metal or ivory lap. Loose abrasives may have been what I was worrying about and abrasive cloth would eliminate much of that fear.
    I remember reading somewhere that burnishing does change the metal structure in a way that reduces the effects of corrosion (?) that might come from contaminates working on the metal. I suppose that would be unlikely in a clock movement that is lubricated and kept in a closed environment.
    Silicon carbide became available long after the classic clock repair writers were through. If Jerry gets the opportunity to cover use of abrasives in clock repair in the Home Shop Machinist I will renew my lapsed subscription. Jerry, be sure to let us know when the issue on optics reaches the newsstand.
    My skill in metal work is barely able to make the runners in brass, let along make a hardened one with a raised edge in drill rod. I do think Jerry’s idea of a filing guide could be made as part of the hinge and should eliminate the tapered pivots that beginners are apt to come up with.
    A few more nights and I’m sure my mind will come up with some idea.
    Again, there are many ways, some good and some bad. There is such a wide variety in the quality of the clocks we work on that one size fits all won’t work. We need to examine them all so we can know and be able to use the appropriate method when the time comes. This message board is a great means to test old ideas and learn new ones. Thank you all for participating.
     
  31. Charles E. Davis

    Charles E. Davis Registered User
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    Bg send me an e-mail and made a suggestion about a runner that would avoid contamination of the pivot by any abrasives in the depression.
    I made a slight adaptation and roughed out a prototype this morning. I used a slitting saw to clear out the rod beneath the pivot but left the bottom of the pocket hole that the arbor fits into. The bottom will provide a stop for end shake while burnishing. Still in brass but this might be easier to make in steel than the original
    It would give more support to the end of the arbor if I would cut the slot with a miniature end mill rather than slitting the outer hub.
    60.jpg
     
  32. Robert M.

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    Jerry,like you I'm not a big fan of burnishing either.Its always been my opinion that the brass or bronze bushing will always be the sacrificial element because of the hardness of the steel pivot as compared to the soft bushing material.I just don't understand how work hardening a cylindrical steel surface is going to benefit the pivot if it is going to be inserted in a soft non ferrous bushing.My own opinion.I follow basically the same procedure you follow with one exception,I finish off with 1000 grit rather than 2000 grit.Just a matter of choice I guess,although I do believe stepping up the grits certainly will make for even a better finish.I've never had a problem with a finished pivot.I check them all with a loupe and I'm more than pleased with the end product.I use my tee rest to support my board and it also gives me a little bit of leverage.I don't have a cross slide for my lathe,thus no tool post.
    I will say this has lead into a great topic whether you burnish or polish your pivots and it also gave us all an opportunity to see a pretty creative gentlemans' handiwork.Me personally,I thought the hinge idea was really slick.Thank you for sharing your idea with all of us.
    Respectfully,Bob Fullerton
     
  33. David Robertson

    David Robertson Registered User

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    I think we may need to clarify what is really happening when we "burnish" a pivot. There seems to be a perception that when we burnish that we are hardening. I don't think this is necessarily so. I think it would take much more force than we could apply with a hand held burnisher to work harden a steel pivot. Work hardening would require plastic deformation of the steel.. I doubt we are doing any plastic deformation when we "burnish" a pivot.

    What a burnisher really does is act like a very fine file.. That is why a burnisher should be prepared for use (or "made") by stroking it cross ways on very fine emory paper. It gives the burnisher some slight roughness.

    I envision an unburnished pivot under high magnification as having peaks and valleys. The burnisher both knocks down the peaks and also bends/smashes them.. thus creating a less variable (and thus smoother/shinier) finish.

    The definition of burnish is to polish or make shiny... not to harden..

    The reason burnishing, when properly done, will produce some black discoloration of the lubricant is that some metal is being removed by the burnisher and contaminating the lubricant.

    For those that use progressively finer emory paper, the proces is similar except the surface of the emory is softer then the steel and probably not much smashing of the peaks is being done.. only removing through abraision.

    If you can be satisfied that no abrasives are being left behind to cause wear in the pivot hole, then I doubt there is much difference in what is accomplished by the two methods.

    Key point... both are CUTTING processes and the work needs to be cleaned well after doing either or debris will be left to contaminate the pivot.
     
  34. Bob W

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    I guess I just as well add some more comments regarding burnishing. I was hoping to have some interesting test data to present but I just haven't had time. I had planned on taking burnished and un-burnished pivots and measuring the surface hardness and get some pictures of the surface textures but seems I just never get around to it. When you are polishing a pivot with an abrasive the surface may appear shiny but will have microscopic peaks and valleys that vary in size by the grade of abrasive used as others have mentioned. Filing will have a different surface texture but will usually still need a polish afterwards. Using something like emory paper will leave peaks and valleys on the pivot that are very sharp, remember that is now we were making our burnish file in the first place. It is the peaks that you get rid of by burnishing as David and others also mentioned. The valleys at the microscopic level will still exist but with a different shape due to the peaks being deformed into them. Moving the peaks is by definition a plastic deformation of the steel; any time you move material and it dosen't return, it has been subjected to a plastic deformation. I doubt that the benefits you get by burnishing is from work hardening but from eliminating the peaks of the surface texture. The smoothing of the peaks will result in an increase in surface area as some others have also mentioned.

    Steel being harder than brass does not mean that it will not wear. In fact when laps are made to size a cylinder bore or create a smooth finish on a hard object, the lap material is typically aluminum or brass. The laping compound (or in our case debris, oxides, etc in the pivot hole) will embed themselves in the brass and then start to wear the pivot as it rotates as some of these are harder than the pivot. Of course there are advantages to soft bores as some of these particles do embed and then don't wear the pivot. A lot of plain bearings were used successfully in nasty environments that would destroy ball bearings.

    Bob W
     
  35. RVC

    RVC Guest

    As an absolute newbie I'm collecting parts and materials and getting ready to start work on my first movement (Hermle 241-840). I appreciate the ingenuity and simple functionality of this device and mean no disrespect to its inventor by wondering about an alternative mentioned in David Goodman's This Old Clock. He suggests a 3/8" variable speed reversible drill mounted horizontally. Seems like it would work and I happen to have one of those drills. Has anyone used this method, or would anyone care to comment on it?

    Thanks.

    Rick Van Clief
     
  36. Robert Gary

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    RVC:

    In the discussion "Pivot Replacement" else where on this board (this link will take you directly to it: old ref::http://nawcc-mb.infopop.cc/eve/forums/a/tpc/f/5746044581/m/4241090751 ), David LaBounty talks about how he used the drill method when he was starting out. Read the entire discussion at this link. I think you will find it very interesting and that you will learn a lot.

    Wecome to the board, and ask questions. That is what it is all about.

    RobertG
     
  37. RVC

    RVC Guest

    Thanks, Robert. I had read through a large part of that link but not enough to notice Mr. LaBounty's comments. You're right - a lot to learn there.

    Rick Van Clief
     
  38. Robert M.

    Robert M. Registered User

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    Not to get off on a tangent but it always impresses me that no matter how much we agree to disagree i.e. burnishing versus polishing,oil sink or no oil sink,or Shellac versus Lacquer we always seem to treat the other persons opposing viewpoint with some level of respect and as a consequence these differences of opinions don't deteriorate into a name calling or cyber screaming match.I haven't changed my opinion about burnishing but the opposing viewpoints certainly have a great deal of merit.Its always an education on this site and I'm glad to be a real small part of of it.The quality of the people who post on this site just can't be beat,even Scotties sorry a** :)
    Respectfully,Bob Fullerton
     
  39. Charles E. Davis

    Charles E. Davis Registered User
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    Here is my latest runner. Rather than cutting the bottom out of the bed there is just a larger hole drilled for the pivot. The arbor is held in the drilled pocket so there is no support under the pivot. You might consider it a tail stock supported steady rest.
    I haven't taken a look to see how many runners will be needed for the various sized arbors in a typical clock.
    This should solve any problem of abrasive contamination or metal particles.

    61.jpg
     
  40. RJSoftware

    RJSoftware Registered User

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    Charlie;

    Keeping in mind that I am a newbie at this.

    Just beginning to understand the need to polish/burnish the pivots.

    (still dont understand diff between polish and burnish)

    but I understand both are necessary methods to smooth out pivots to avoid power loss.

    About your device. How do you (or do you?) hold a pivot file against the pivot and use squeegee to turn the gear?

    What assures squareness of the file against the pivot? If you use the edges of your device, how do you know they are cut square?

    Then do you polish with emory cloth?

    RJ
     
  41. Charles E. Davis

    Charles E. Davis Registered User
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    #41 Charles E. Davis, Sep 5, 2005
    Last edited by a moderator: Sep 8, 2013
    RJ
    I am answering your questions one at a time.

    Polishing uses abrasives to give a flat, finely finished surface to the pivot.
    Burnishing uses a very fine file (pivot file) to “remove” metal, if necessary to make it smooth, and then a burnisher to “move” metal to squash down any high places into lower ones. It also compacts and smoothes the finish of the pivot.

    As a general practice a person does one or the other. Small hard steel pivots, like French clocks, do not respond to filing and burnishing so your only option is polishing (grinding) the surfaces to give the desired finish. American style clock pivots are made with soft pivots and they respond better to filing and burnishing. The usage of abrasives on soft steel is questionable.


    The file or burnisher is placed against the pivot and then moved back and forth, pressing down against the pivot that is held by the runner. With the file the hands move in opposite directions and the filing stroke is very deliberate so it is only in contact while the file is moving away from you. In the burnishing stage the see-saw motion assures that the burnisher is always moving against the turning direction of the burnisher.


    With the burnisher you are not removing metal so the tool will maintain the parallel sides of the pivot. One has to use care when using the file to maintain that configuration.


    Any sheet material will be glued to a strip of wood and used like a file. One can also get hard stones in the same shape and dress pivots with them. When “loose” abrasives are used they are generally mixed with oil and applied to either wood or bell metal flat rods that are very much like a burnisher.

    As I mentioned earlier, the two methods are used independently based on the hardness of the pivots. Each has their place and in that circumstance is “the best.” In this case, “one fits all” doesn’t work!
     
  42. RJSoftware

    RJSoftware Registered User

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    Charlie;

    Thanks for the detailed answers, much apreciated.

    A couple more questions, if you don't mind :)

    I checked on ebay for burnishing and pivot files.

    I see a left and right pivot file and a combo pivot file and burnisher.

    Could you explain these? (Why left & right etc)
    Which do you recommend?

    They are expensive!

    Is there a cheaper acceptable way? (Like the stone sounds promissing).

    About the burnisher. So it actually moves the metal...and polishes it?

    What in the world is it made out of? How does it move the metal, via heat from friction?

    Thanks again.
    RJ
     
  43. Bob W

    Bob W Registered User

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    I have been working a little at a time to gather some very interesting pictures (no hints on the type yet!!) of polished and burnished pivots. The pictures are complete and I think you guys (and gals) will find them very interesting but I need to put them together into a PDF document that will have text description of the information presented. I am getting to the point that I need a good way to post this or make it available. I am not sure of the size yet, but the pictures and text individually are around 750K at this point. Do you have any suggestions on how this could be posted?? I really hope this will be interesting to the group, and I did have some fun doing it.

    Now to RJ's question. I made my burnishing file from an old needle file that had top and bottom safe sides and cutting edges. Ground the edges smooth with a bench grinder, pulled it across some 320-400 (forget which) silicon carbide paper to create the surface required and was done. Almost no cost involved except fot the dollar or so I had in the file. I also have some carbide lathe tool bits that I played around with that work OK too, although more expensive.

    When I get the pictures posted you will see that surfaces that may look smooth and polished are not. They are composed of ridges and valleys created by the machining processes. Abrasives such as stones and emory cloth actually leave microscopic grooves that become the bearing (although somewhat poor) surfaces of the pivot. Burnishing can 'wipe' the peaks leaving a much better bearing surface with the peaks removed. It is a combination of plastic deformation (moving the metal) and removing material (notice the black residue?).

    Bob Whiteman
     
  44. Tom Chaudoir

    Tom Chaudoir Guest

    Hi Bob,

    Thanks for being willing to share. PDF may not be the way to go. It doesn't do well with image intensive presentations.

    The easiest way would be to make a Flickr album. It's dead simple to use, and you can put text with each image.

    I use Blogger for this sort of thing, because I like the flexibility. Here's an example. A fellow tried to repair the governer on his cuckoo clock's music movement, and broke a pivot. He bought a replacement and it didn't fit. (They almost never do.) I told him that if he sent it to me, I'd fit the governer, and show him what I did.

    Try either one. If you get stuck, drop me an email and I'll help you through it.

    Regards,
     
  45. RJSoftware

    RJSoftware Registered User

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    Hey David;

    A few questions if you dont mind.

    The refference I see to pivot files being left or right. What is this something lathe specific?

    Me, I plan to simply use drill and put other arbor in chuck. Place pivot to be worked on in slot carved in wood and press file against it.

    After I grind down a touch (dont know how much) to make cylindrical. Wondering if I should use oil while filing?

    Clean off area and pivot.

    Use same arrangement to burnish. Some strong square flat piece of steel that is shinny smooth. Then hold against wood block and spin with drill. Maybe use oil.

    Dont really see need to score surface of burnishing tool...

    Any opinions apreciated.
    RJ
     
  46. eskmill

    eskmill Registered User
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    Pivot files and burnishers have a trapzoidal shape. The flattest part of the file or burnisher surfaces the pivot and the edge surfaces the arbor shoulder.

    It makes a difference if the tool is held beneath or above the pivot being resurfaced and/or the direction of spindle rotation.

    You may use oil while burnishing but kerosene, the "mother's milk of horology" is prefered.

    The burnisher will be most effective if it is not mirror finished. It should be grained cross-wise by thrusting the burnisher sideways across some sharp 320-400 grit carbide abrasive paper stretched tightly across a very flat surface. One good firm stroke is plenty; more strokes spoils the effect.

    Don't run your drill-motor lathe at full speed. Use a variac or variable light dimmer control to limit the speed.
     
  47. Tom Chaudoir

    Tom Chaudoir Guest

    A pivot file is generally used to reshape a badly worn pivot. After that comes burninshing.

    There's another element at work here, and a good reason for having a solid support under the pivot. You want to really bear down while burnishing. It very slightly deforms the surface, like a tire going down the road. The surface becomes work hardened for better wear. If you simply hardened the pivot by heat treating, it would be too brittle. Think of the hard coating on an M&M.

    Regards,
     
  48. RJSoftware

    RJSoftware Registered User

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    Thanks all for keeping up with this thread.

    Ok, I take it that the right/left really has to do with using a lathe (from top or bottom).

    What is this, is this just a lathe use technique choice? To use top or bottom...

    I'm trying to understand this before I purchase this tool. It is expensive.

    I'm thinking that maybe there is issue over right left because of the direction the pivot file's teeth are angled. I know some files have teeth that groove in angular direction while others straight across.

    Is this what the issue is? Are they supose to push the filings outward maybe? Keeping the filings from rolling arround and pitting pivot surface...?

    So, they are trapezoidal. Why did they bother making them trapezoidal shaped? Why not just rectangular, since the "quote" flattest side(my thinking widest) part goes against pivot.

    Then they could have made right and left one on each side... true?

    I apreciate your patients and your comments.
    Thanks
    RJ
     
  49. David Robertson

    David Robertson Registered User

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    RJ,

    The acute angle allows you to get in the corner between the pivot and the shoulder and keep that as square (i.e. no radius) as possible... a square corner on the file will not be perfectly square for long, so the acute angle compensates for this. A radius in the pivot/shopulder intersection is not desireable... it can "jam" in the pivot hole.

    I have used pivot foles and burnishers with rectangular cross sections and as long as they are still reletively square, they do ok...


    David
     
  50. RJSoftware

    RJSoftware Registered User

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    David;

    Thanks for quick reply.

    Do you do up or down, use left or right and tell me is there any particular reason?

    RJ
     

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