Jewel Position, Pivot Length and Cap Jewel

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  • #49104
    david pierce
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    Most repair books and videos stress measuring the position of the balance jewel with the micrometer adjustment on the Seitz Press. This is to put the replacement jewel back into the proper position. Unfortunately when this is done the watch may still not work. There have been a few posts on this and other forums about watches not running when put in the face up or face down position. From what I can tell in almost every case, the slowing down or stoppage of the balance wheel was due to the balance staff cone comming into contact with the jewel. The common wisdom when repairing a watch is to identify the broken component, find the exact part number and purchase the exact replacement part from a supply house. As most of you know this is usually difficult to do and sometimes impossible. The older watches are no longer made and the companies that made them are not in business anymore.
    This does not mean that the watch cannot be put back into working order but, in order to do this, there must be an understanding of the relation and functions of the staff, pivot, pivot jewel and cap jewel. The good news is watches are not super ultra precision items and some working tolerance is provided. Like most things watches are the result of comprimises. A larger pivot is stronger and less likely to bend or break but it also introduces more friction and therefore requires more power from the train. When replacing a broken staff with another staff this should be considered. A larger pivot and accompaning jewel may work but it may also put a power drain on the system due to increased friction. This could slow the watch down but it may be possible to adjust around this.
    The overall length of the staff is important as the pivots on each end must be slightly shorter than the distance between the cap jewels. This clearance is called end shake.
    The pivot length is important because the end of the pivot must come in contact with the cap jewel and prevent the cone of the balance staff from contacting the balance jewel. If the pivot is too short it will not make contact with the cap jewel. The reason olive jewels are used in this application is to allow clearance for the cone of the staff.
    This brings us to the position of the balance jewel. This must be set between the balance staff cone and the cap jewel in such a way that it will not come in contact with the cone. The measurement of the previous jewel position may not be the correct measurement. The correct working measurement can be found through trial and error by adjusting the Seitz micrometer and repressing the jewel until the correct distance is found.
    david

    #58283
    tmac1956
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    david:

    That is a very relevant and helpful post. I probably should print it out and post it somewhere nearby. I see this problem a lot.

    Later,
    Tom

    #58284
    bernie weishapl
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    Thanks David. That is some info going into my library.

    #58285
    bobpat
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    David, Great bit of info, Exactly the process I am at with my watch

    #58286
    michael weaver
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    I love coming back here after my long time away to read your posts. Just sent you an email too. I might give you a shout tomorrow.

    #58287
    david pierce
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    • Topics Started: 90
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    Mike,
    It is always good to hear from you. I hope you are still working on watches and learning about them. At this point I don’t think anyone can know everything there is to know about how these suckers work no matter how much time and training they have had. I like this forum because different ideas can be presented withrout a barage of nasty comments comming back. Even a wrong suggestion can invoke a thought process that we can all learn from if we want to. Sit back and enjoy the learning experience.
    david

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david pierceJewel Position, Pivot Length and Cap Jewel