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  1. TheNewOmegaMan Oct 15, 2020

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    Hello everyone! I hope all is well. I have recently been exploring watch tinkering and just purchased The Joseph Bulova School of Watchmaking Training Manual, which is on its way in the mail. I wanted to learn more about watch repair and how they function. I have a question about amplitude. I know amplitude is the measure of the amount of rotation in the swing of the balance wheel, in either direction, usually expressed in degrees. From reading various online papers, I found that one can tell the health of a watch movement depending on the amplitude number that you get. My question is, how do you know the amplitude range for a watch? Does it differ depending on the movement and age? Is it something you have to become familiar with the more you test the watch or are there "amplitude standards"? I have seen the numbers 250-300 for vintage watches and 275-315 for newer models. I also noticed people reporting lower numbers and stating that the movement was very healthy. I wanted to get some feedback on the subject.

    Thank you.
     
    Edited Oct 16, 2020
  2. Canuck Oct 16, 2020

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    I have the Joseph Bulova School of Watchmaking, 9th edition, from 1968. If the edition you are waiting for hasn’t changed from my 9th edition, you will find there is no index to assist you in researching the topic of amplitude. You’ll likely have to read the whole book to glean snippets of information that discuss amplitude. You will learn lots about the design and structure of watches from 50 years ago, and much before that, from the Bulova book. But after you peruse it, you‘ll likely find you have hardly scratched the surface of what comprises modern watches.

    When you plod through the a Bulova book and come up short on the topic of amplitude, I suspect you will find there is a lot more information in this MB archives regarding amplitude, than you’ll likely find almost anywhere else. Amplitude stats on the performance of a given watch are not the be all and end all pertaining to the condition of a given watch.
     
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  3. Marsimaxam Oct 16, 2020

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    Interesting and I wish you well in your pursuit of learning watchmaking skills, an admirable trade or hobby.

    But, I was told there would be no math.
     
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  4. TheNewOmegaMan Oct 16, 2020

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    Thank you Canuck. I have a lot more research to do my friend.
     
  5. Archer Omega Qualified Watchmaker Oct 16, 2020

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    Back in the times before there were timing machines that would actually tell you the amplitude, watchmakers would look at the balance and judge by eye if it had "good action" or not...and if it looked okay, they didn't worry about it too much. Some still don't consider it important.

    In modern watchmaking things are a bit different. Companies have standards for minimum, and often maximum, amplitude. It will vary by the movement, so there really is no "one size fits all" answer to what good amplitude is. Where specs from the maker aren't available, some judgement is involved. Also knowing how the amplitude numbers in each position relate to each other is important.

    Most companies do not have a minimum amplitude requirement at full wind. Instead they give you a minimum amplitude number at 24 hours after full wind. Even within one maker of movements, the standard for the movements will vary, so what might be good minimum amplitude for one movement won't be sufficient for another.

    What some companies will do is give you a maximum amplitude number at full wind, and this is to ensure that the amplitude doesn't get so high that you encounter rebanking. This is where the roller jewel travels far enough around to strike the outside of the pallet fork horn, and then it will bounce back quicker than the balance spring would normally return it. It will then bounce back off the other fork horn, and the cycle repeats - this leads to a very fast rate.

    There are some companies and movement that are known not to have high balance amplitude. Seikos for example (in particular the cheaper kind) will often not have balance amplitudes over 250 even when brand new at full wind. There are some Omega movements that also don't often have high balance amplitude. So there is some experience required to understand what the movement should have.

    There's no simple answer to this unfortunately, but the numbers you have given above in your post, those ranges are a good starting point. However for vintage watches there are many that will have the amplitudes you are saying for modern watches. One common issue I run into on Cal. 321's for example is amplitude that is too high, causing rebanking. These watches will begin to rebank around 305 to 310, so often after a full service the movement is rebanking on these.

    Hope this helps.

    Cheers, Al
     
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  6. TheNewOmegaMan Oct 16, 2020

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    Thank you so much Archer! I really appreciate you taking the time to chime in. It is definitely becoming a lot more clear to me now.