Son of a preacher - man!

Discussion in 'Clock Repair' started by peanuts, Oct 7, 2019.

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  1. peanuts

    peanuts Registered User

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    #1 peanuts, Oct 7, 2019
    Last edited: Oct 7, 2019
    I recently made a mess of opening up a hole for a bushing (don't ask; I'm new to this...and dumb!), so knew I had lost centre (USA: center). Time for a preacher...

    I looked at the designs I could see on the message board, and decided to make an adjustable one, rather than a fixed one. I copied - as best I could - the design in the one pictured here: Best measuring instrument

    When I tried to use it i realized that after I transferred the preacher from the 'good' plate to the 'bad' plate, it was canted over at an angle because the pin that was over the problem hole was now in contact with the plug I had made, so much higher. I tapped the pin anyway and drilled a hole at the spot. Suffice it to say, it was not centred.

    I also realized that the two 'good' reference pivot holes were different diameters, creating another problem if the two relevant pins were the same depth.

    So I spend a happy few hours making preacher that would overcome these problems; i.e.:

    a) the pin for the 'bad' hole needed to be capable of being raised and lowered without affecting the triangulation of the other two pins.
    b) those other two pins needed to be height-adjustable, prior to setting up the triangulation.

    This is what I came up with:

    2019-10-07 13.20.39.jpg 2019-10-07 13.20.53.jpg
    In the first picture (all the pins are vertical; camera distortion makes them appear otherwise...):

    (a) The pin on the left is a close fit and relatively free to float up and down, and that is the pin for the 'bad' hole, and the one I will tap to mark the plug.
    (b) The brass cylinders above and below that pin ensure minimal deviation of the pin from vertical
    (c) The lower brass cylinder rests against the plate.
    (d) the two brass cylinders on the right are threaded and allow finger-tip tightening when setting the triangulation.

    In the second picture, you can see how I made the self-locking nuts captive, so that the pins would not change height when setting the triangulation.

    I'm wondering now whether I overthought this, and made work for myself.

    I only just finished making this, and have yet to use it to see if it is accurate. So my question is: before I do, can anyone foresee any problems with its accuracy?

    Simon
     
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  2. David S

    David S Registered User
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    Looks good. To check it out, find a location with three pivot holes that aren't worn and set the preacher to the holes in the bottom plate then see how the preacher lines up with the corresponding holes on the top plate.

    David
     
  3. shutterbug

    shutterbug Moderator
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    Remember that you'll be on the outside of one plate and the inside of the other to get proper alignment.
     
  4. Jerry Kieffer

    Jerry Kieffer Registered User
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    Simon
    Based on your comments, my understanding is that you have a hole, but have lost the original position of the pivot hole.

    At this point, the only proper effective way to find proper positioning of the Arbor pivot in relation to the next arbor is by the depthing process. The "preacher" offers no such option.
    Assuming that you do not have a depthing tool or are using a Mill to bush, there is a simple hand method of depthing in place.
    The following is a posted response to another person who had a similar issue with both bushing and depthing. Depthing is covered in the second half of the response and can be applied to your situation.

    Jerry Kieffer

    _____________________________________________________________________________________________________________________________________________



    When you look at a elongated pivot hole you of course have a problem.

    You will certainly court trouble if you create more issues.


    (1) If you file another cavity on the opposite side you now create an even larger issue fugitively speaking.


    (2) With this larger now really odd shaped hole, attempting to locate a center you have permanently removed can be a challenge. Especially with a tapered broach that will take the path of least resistance.


    (3) assuming you get lucky and the broach centers on the original location, you now have a tapered hole for a non taperedbushing.

    Certainly not an ideal mechanical solution.



    For the beginner who is bushing for the very first time, challenges such as these are best avoided where possible and certainly avoidable in this case.


    A logical set goal would be to predetermine where a bushing should be located and provide a method that would assure that location when drilling or using a bushing reamer for proper fit of the bushing.


    If cost is a concern on the initial attempts, I would suggest the following method.


    (1) locate a flat piece of steel about 8" long and drill a bushingsize hole in the middle of it.


    (2) position the hole centered on the original pivot hole (Whats left of it) to be re bushed under magnification and clamp on both sides. (Per attached Photo)


    (3) This will provide a guide when drilling or reaming assuring the predetermined location of the bushing hole removing all of the "Luck" and drama. It also provides non tapered bushing holes for proper mechanically fit bushings.


    This method can also be used to correct poorly positioned bushing jobs.


    (1) remove the existing bushing and reassemble the movement with poorly bushed arbor and next arbor.


    (2) Install a bushing in the hole in the flat piece of steel and place the bushing/steel over the pivot with the poorly placedbushing.


    (3) This will now allow you to depth the two arbors in place by moving the bushing/steel until ideal depth is achieved. Then clamp in place.


    (4) disassemble the movement, push the bushing out of the steel piece from the back side and redrill/ream the proper depthed location assured by the steel guide.


    While these methods are not fast enough or efficient enough for everyday general repair, they offer the beginner an option for quality work with out experience and minimal cost.


    Jerry Kieffer

    Attached Thumbnails

    DSCN5565.JPG
     
  5. RJSoftware

    RJSoftware Registered User

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    #5 RJSoftware, Oct 7, 2019
    Last edited: Oct 7, 2019
    A compass works too. Scribe faint lines from neighboring holes. X marks the spot.

    Your design is pretty good. The compass sort of suffers the same pin problem but since only one rest in hole and other scratches surface there is no need to worry about all pins in at different conditions. The only issue is not losing the distance measured.

    Rj
     
  6. gleber

    gleber Registered User

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    Hi Jerry,

    How does this work if the arbor is only long enough so the pivot does not extend past the outside edge of the plate? Most arbors don't, so I don't see how you would place the "bushing/steel over the pivot" and "capture" the pivot if the it doesn't protrude out of the plate?

    Tom
     
  7. Jerry Kieffer

    Jerry Kieffer Registered User
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    #7 Jerry Kieffer, Oct 8, 2019
    Last edited: Oct 8, 2019
    Tom

    I will explain, but provide a sketch if required.

    There will always be exceptions to any procedure, but in this case easily over come if required.

    First, in most common US 8 day movements, the pivot will extend above the plate if the lower pivot is pushed flush with the bottom plate and supported.

    If not, substitute a length of bushing wire for the bushing with the end sharpened like a pencil. It should be sharpened just enough to capture the pivot inside the enlarged bushing or potential enlarged bushing hole as in this case.

    Jerry Kieffer
     
  8. peanuts

    peanuts Registered User

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    Although I had realized that, what hadn't occurred to me was that the pins would seat deeper in the front holes (i.e. those with an oil sink) than holes in the back. I'm re-thinking my design...

    Forgive my ignorance Jerry, but if I manage to re-establish centre, won't the depthing be the same as before? I must be missing something because I know you know what you're talking about!

    I thought about doing that, because I have a pair of dividers (sharp points on both arms, in case the terminology is different in American English) but I was worried about scoring the good holes.

    Simon
     
  9. Jerry Kieffer

    Jerry Kieffer Registered User
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    Simon
    Depthing, is the most accurate way to test and assure that you actually have the position of least resistance. In most cases that will hopefully be the original pivot location. However there are rare exceptions and that is in part why some movements run better than others. Again however, the procedure is one method of assuring proper pivot location and then assuring that the bushing will be centered to the depthed location. It was offered as an option for those who prefer methods that test and assure an accurate outcome.


    Jerry Kieffer
     
  10. gleber

    gleber Registered User

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    Thanks Jerry,

    I guess I need a sketch of this method. I can't picture it.

    Thanks again,
    Tom
     
  11. Jerry Kieffer

    Jerry Kieffer Registered User
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    Tom

    The first attached photo shows a typical pivot extended about .015" above the plate surface. While more than enough for a bushing to catch for depthing, it is not noticeable unless you are specifically looking for it.

    The quicky second photo/sketch shows the bushing wire explanation to catch a pivot flush or just below the plate surface.

    The third photo shows the setup utilized for depthing with a milling machine when this tool is also used for bushing. In this case, a stake from a watchmakers staking set can be used to engage the pivot for depthing by moving the slides. One feature of this setup, is that you are able to depth a arbor with additional arbors before and after the arbor being depthed unlike commercial depthing tools. This would be done when occasionally three wheels and pinions are close to being in line on the same side of the movement, allowing three arbors to be depthed at the same time.

    Jerry Kieffer

    fullsizeoutput_435.jpeg fullsizeoutput_436.jpeg DSC00048.jpg
     
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  12. peanuts

    peanuts Registered User

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    Thanks for the clarification, Jerry. I can see the benefit, and I think that's a genius way of achieving it. I do have a mill, so I'll try that out on a scrap movement first.

    Simon
     
  13. RJSoftware

    RJSoftware Registered User

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    the most common depthing tool found are watch sized. You can build your own for clock size using punches from an old staking set.
     
  14. Uhralt

    Uhralt Registered User
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    In most American clocks the pivots do extend over the plates. Otherwise the infamous Rathbun bushings, that are screwed on top of the plate, couldn't work.

    Uhralt
     

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