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  1. #1
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    Default Using glass for bushings

    Hello!

    I'm slowly working my way towards constructing a clock from an existing motion work. I went over my plans with a watchmaker friend of mine and he pointed out that my plan of straight motion works might not be such a good idea. Apparently a student at the school where he teaches made such a clock that developed meshing errors. Wether it was from construction error or wear wasn't clear but it didn't work, is the bottom line.

    Construction errors will have to be dealt with by careful construction but the wear supposedly stems from all the wheels having the same load direction and so the error from wear accumulates at the escape wheel. So I thought I might use jewels to reduce the effects of wear!

    Jewels in these sizes seem to be close to impossible to find and those close are expensive. I thought I might try to grind glass bushings to suit my needs, from plate glass. Does anyone here have any suggestions or deterring advice on using glass for bushings? It seems to suit my needs, it's hard easily obtainable and present in sections more easily worked than lapidary blanks.

    All help appreciated!
    Karl

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    Default Re: Using glass for bushings (By: karlmansson)

    Jewels are used to reduce friction not to reduce load wear.
    Tinker Dwight

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    Default Re: Using glass for bushings (By: Tinker Dwight)

    Well, yes...? And friction causes wear. Worn jewels are much less common than worn brass bushings in my experience. I also see that LeCoultres table clocks with straight motion works have jeweled bushings. If I can reduce friction, and thereby wear, wouldn't it extend the service interval and function of the clock?

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    Default Re: Using glass for bushings (By: karlmansson)

    What's the significance of "straight motion works"

    Phil

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    Default Re: Using glass for bushings (By: Phil Burman)

    Hi Phil!

    I should have elaborated on that... In line motion works, in that all wheels will have their bushings in a straight line between barrel arbor and pallet arbor.

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    Default Re: Using glass for bushings (By: karlmansson)

    Quote Originally Posted by karlmansson View Post
    Well, yes...? And friction causes wear. Worn jewels are much less common than worn brass bushings in my experience. I also see that LeCoultres table clocks with straight motion works have jeweled bushings. If I can reduce friction, and thereby wear, wouldn't it extend the service interval and function of the clock?
    You can use less drive force with jewels and have less wear.
    It is not friction that is causing wear. It is the dirt that gets
    in the oil plus the force between the surfaces.
    Don't equate friction with wear.
    Tinker Dwight

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    Default Re: Using glass for bushings (By: karlmansson)

    Personally I don't think glass is hard enough, you can get sapphire watch crystals in various thicknesses, cut your "jewels" from that, what about just using micro ball bearings.

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    Default Re: Using glass for bushings (By: dAz57)

    I had also considered using glass as a 'jewel'. My idea was to use Pyrex capilliary tube & simply cut short pieces off. I found suitable tube available for a 1 second pendulum clock train. I did not proceed with the idea.
    For small ball bearings Google Boca Bearings in California. Excellent data on all their bearings - sizes, load ratings etc. For clocks best are all ceramic but they are expensive - especially when shaft is <3mm. I use hybrid bearings - stainless steel races with ceramic balls. Wash all the grease out - soak them in engine cleaner and spin them in running water.

    For commercially available jewels there is Swiss Jewl in USA http://www.swissjewel.com/2/ring_jewels Trouble is they only list imperial sizes.

    Another US source http://birdprecision.com/bearings2/Ring_jewel.pdf

    There is a very informative Wiki post (sourced from Bird I suspect). https://en.wikipedia.org/wiki/Jewel_bearing

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    Default Re: Using glass for bushings (By: tok-tokkie)

    In all fairness, the grit that enters the oil also adds to the friction, causing wear. Of course, at Clock with dried up, Clean oils can fail to run where the same Clock with fresh oil, contaminated with abrasives, will run but wear itself down. I Think there is a difference in those cases though as the first instance is adhesion and the second friction.

    Yes, ball bearings are probably the way to go! But why wash the grease out?

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    Default Re: Using glass for bushings (By: karlmansson)

    I keep reading about butter bearings when searching for ball bearings for this application. Are they a good and price efficient alternative in your expereince?

  11. #11
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    Default Re: Using glass for bushings (By: karlmansson)

    The grease is washed out for two reasons. Firstly for endurance. The grease will harden as the solvents evaporate over the years. Secodly to reduce the torque. Without grease the bearings spin much more freely.
    Here is a link to a good paper about them. http://www.dg-chrono.de/fotohome/ima...e045a520e5.pdf

    Butter Bearings are conventional carbon alloy steel minature ball bearings. They get their name from Mark Butterworth who supplies them. He is active on this site. http://muscatinejournal.com/news/loc...9bb2963f4.html

  12. #12

    Default Re: Using glass for bushings (By: tok-tokkie)

    I'm in the process right now of making jewel bearings for a regulator I'm almost done with.

    Cutting the raw ruby boule, and then roughing it round Click image for larger version. 

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    Grinding round Click image for larger version. 

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    Drilling and cupping Click image for larger version. 

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    Grinding the face, and the apparatus Click image for larger version. 

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    The process, while somewhat lengthy, isn't impossible, even with old, fat, beat-up fingers. I've made quite a bit of the tooling myself over the years. The next stage is polishing the outside edge, front face, and oil cup with finer and finer diamond paste. After that, while the jewel is still concentric on the brass tube, I'll size and polish the inside bearing surface with a small needle shaped polisher I built. Finally, I'll reverse the jewel on the tube, and grind and polish the other face. I'll post pictures as I complete this process, if there is interest.

    I guess the point is to encourage the OP to take a swing at what you want to do, even if you use glass as the material. The raw ruby isn't that expensive, though, and makes a really attractive classic bearing.

  13. #13

    Default Re: Using glass for bushings (By: karlmansson)

    John,

    I'm very interested in the process you have been using to make your own jeweled bushings. While I have contacted the suppliers listed previously, they did not really have the sizes I wanted and didn't really want to work with a hobbyist.

    If you have time, please provide more details along with suppliers for the raw material and type/grade if that's the correct terminology.

    Best Regards.

    Carl

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    Default Re: Using glass for bushings (By: karlmansson)

    Quote Originally Posted by karlmansson View Post
    I keep reading about butter bearings when searching for ball bearings for this application. Are they a good and price efficient alternative in your expereince?

    Yes.

    Glen

  15. #15

    Default Re: Using glass for bushings (By: cmnewcomer)

    Quote Originally Posted by cmnewcomer View Post
    John,

    If you have time, please provide more details along with suppliers for the raw material and type/grade if that's the correct terminology.

    Best Regards.

    Carl
    Carl -- the boules can be bought at gemcutter.com - a quick google search brings up lots of others. Diamond drills can be bought at Rio Grande Albuquerque, Lasco Diamond, and MSC. The diamond paste I also get from Rio Grande Albuquerque riogrande.com -- I use 325 grit for rough grinding, 1200 grit for smoothing, and 14000 grit for final polishing.

    There is a good write-up on the process in George Daniels "Watchmaking"

    Best of luck,
    Johnny

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