Center Wheel Stripped Off Pinion

Discussion in 'Watch Repair' started by 12V6GT, Jan 1, 2019.

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  1. 12V6GT

    12V6GT Registered User
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    Jul 10, 2011
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    Well, it was going well until...

    I've had this old Swiss 12s / 18 Lignes movement running at my desk for some two years. Then the mainspring gave way. I ordered a replacement New York Standard 16s spring for a replacement. It came. Today I put it in and wound the movement... only to have the center wheel pinion spin loose of it's press fit on the center wheel gear. So now the repair is beyond me. Oh well, too bad as it had a good balance staff. This movement I assume has been worked on a lot since it looks like somebody put jewels in the top plate while the bottom plate has no jewels.

    Sorry, I don't have a picture of the center wheel and the problem. The center wheel had a large whole in the center so that the center wheel was pressed right over the pinion gear. I first thought it had been repaired but the next wheel down was made the same way. The pinion gear leaves look like they dug into the brass wheel pretty good. This Waltham center wheel looks similar except my center wheel pinion is all one gear. No step for the center wheel to press on to.

    Anyway, I guess the only hope is to find a center wheel now. Probably isn't going to happen, especially for an old keywind Swiss movement.

    189855-IMG_0361.jpg 189855-IMG_0362.jpg Screenshot_20190101_170638.png
     
  2. Skutt50

    Skutt50 Registered User

    Mar 14, 2008
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    Nor always, but even cheap swiss movements often have jewels for the balance. I have seen some movements with only one jewel and guess where it was located? Where it would be visable i.e. an end stone in the balance cock.

    From the looks of the movement design, the balance should be mounted in the top plate.......You may find the bottom jewels "inside" the movement and not in the main plate.

    A loose center wheel is of course a problem. (I assume it is not a safety pinion.) This may have happened when the mainspring broke. I have had some success by closing the hole by moving material towards the center in a staking tool. The hard thing is to re fit the wheel and getting it in the center. Again I use the staking tool to press/punch the wheel back on the arbor.....
     
  3. 12V6GT

    12V6GT Registered User
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    Jul 10, 2011
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    I had the movement completely apart and had just put it all back together for storage when I wrote this. There are no jewels on the bottom plate except for the balance which is actually on the top plate. But yes, point taken. It for sure could have been manufactured that way.

    You are correct, no safety pinion. When I replaced the main spring I had just about completed winding it when the center wheel gave way. The New York Standard replacement spring probably was a little to strong for it. The spring that was in it was .19 and the NYS was .22 so that may have caused the problem. Not sure how much that would impact it. Apparently a lot. :) I thought about staking it again but felt there was too much pressure there for it to hold with what little material is left.

    Thanks for you comments Skutt50. Appreciate.
     
  4. DeweyC

    DeweyC Registered User
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    Feb 5, 2007
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    You have a couple choices with the existing center wheel. But they require lathe skills.

    If room permits, lower the seat on the pinion. First bore the wheel true.Then turn the seat to take a driving fit and then swage. When working on a pinion, fill the leaves with shellace to avoid tearing. Very sharp graver and light touch. Minimum overhang of pinion, only as a much as the seat to be turned.

    Else, over bore the center wheel and fit a plug you can rivet from both sides. Bore this to a driving fit on the existing pinion seat. Then driving fit and swage.

    Before something like this, I measure the pinion in case something goes south. Leaf count and OD (drill guage) is all you need to order a cutter from Thornton or to pick a pinion from a selection (should you be so lucky).
     
  5. Skutt50

    Skutt50 Registered User

    Mar 14, 2008
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    I think the change from .19 to .22 is a bit too much. If the new spring is the white type, and the old was blue steel, this will also add to the strength. There is a good possiblility you will get some knocking since the amplitude is likely to increase quite a bit.

    Before you installing the repaired center wheel I would locate a weaker mainspring.......
     
  6. gmorse

    gmorse Registered User
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    Jan 7, 2011
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    Hi 12V6GT,

    The strength of a mainspring is proportional to its width, the cube of its thickness and the inverse of its length, so the seemingly small difference in the thickness of your replacement spring is quite significant, (cubes are 0.006859 against 0.010648). I don't agree that the alloy springs are necessarily stronger than the old blue steel ones for the same dimensions however. See David Boettcher's website on mainsprings, which is useful and informative.

    Regards,

    Graham
     
  7. 12V6GT

    12V6GT Registered User
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    Thank you Graham, Dewey, and Skutt50 for your comments and suggestions. I too agree I screwed up with the main spring decision. The one time I went with a smaller strength the watch didn't have as good of an amplitude (it was also a little shorter) so decided I should go up in strength. What I didn't realize is it could tear up the center wheel. :) I could have dealt with the knocking. :) But your points are well taken. There's just no substitute for the right mainspring. This one was a white alloy one as well and it was substantially stiffer. :( My bad. I guess the rule should be to go thinner if one can't find the right spring.

    Dewey, thanks a million for your suggestions on how to fix the center wheel. Those are good suggestions. They are currently beyond my abilities but I may eventually revisit this movement when I want to frustrate myself again. :)

    Thanks again everybody.
     

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