Mechanical accuracy
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  1. #1

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    Mechanical accuracy

    Hi guys,

    Im kinda confused about the accuracy of mechanicals, I keep getting varying answers.

    How many secs does the avg mechanical (not COSC) lose or gain a day?
    Is +/- 10s normal? Ive been told by my jeweler that +/- 2 or 3 secs a day can be expected.

    Also, what is the range for a COSC certified watch?

    And after wearing the watch for a while and getting it regulated how much more accurate does it become?

    Sorry for all the questions but I would be grateful for some solid ans.

    Thanks

  2. #2

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    Re: Mechanical accuracy

    It's rare to find a mechanical watch accurate to less than 10 seconds a day. Someone correct me if I'm wrong, but ten seconds might even be considered very good on the accuracy range for mechanicals.

    But even if was very accurate, it could easily lose its accuracy with a minor shock such as bumping into a wall, which would knock everything out of whack.

  3. #3
    Member Docrwm's Avatar
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    Re: Mechanical accuracy

    The accuracy of mechanicals varies widely from crazy erratic for cheap watches that have not been regulated and have poor tolerances to precision chronometers. If you want the highest precision then by a $5 quartz watch (the folks that talk about $K quartz watches are talking about such small increments of improvement its amazing).

    The Eta 2824 is the workhorse auto movement among the Swiss movements today and considered a pretty good movement. The standards for its various grades (yes all 2824s are not created equal) vary according to the components in the movement.

    This is taken from a review I wrote on the Affordables forum at
    https://forums.watchuseek.com/showthread.php?t=46610

    "The performance differences are the big differences between the various grades: ("The limit values are subject to interpretation: 95% of the pieces delivered in a lot must be within the specified limits.")

    Standard:
    2 positions (CH, 6H)
    daily rate: +/-12 sec/day
    Maximum positional variation: 30 sec
    Isochronism (between 0 and 24 hours): +/- 20 sec

    Elabore:
    3 positions (CH, 6H, 9H)
    daily rate: +/-7 sec/day
    Maximum positional variation: 20 sec
    Isochronism (between 0 and 24 hours): +/- 15 sec

    Top:
    5 positions (CH, FH, 6H, 9H, 3H)
    daily rate: +/-4 sec/day
    Maximum positional variation: 15 sec
    Isochronism (between 0 and 24 hours): +/- 10 sec

    Chronometre:
    As per COSC specifications, which as far as most owners will notice, isn't much different from Top grade."
    -Robert
    Buy what you like, keep what you love, don't spend too much.
    As long as you follow those simple rules - you shouldn't listen to anyone about your watches.


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  5. #4

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    Re: Mechanical accuracy

    Thanks a lot for the information much appreciated.

    I wasnt planning on buying a bad mechanical so that reference is irrelevant.

    I was looking at the Hamilton jazzmaster or the mont blanc timewalker auto.

    The mont blanc styling really appeals to me but I wasnt sure what accuracy I should expect in the first few mnths before regulation and then after having it regulated. I have always relied on my trusty tissot so I was just wondering.

    BTW a watch is considered COSC if it can do +-4 secs a day?? Am I right?

  6. #5
    Member Zennmaster's Avatar
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    Re: Mechanical accuracy

    Quote Originally Posted by faraday View Post
    BTW a watch is considered COSC if it can do +-4 secs a day?? Am I right?
    Yes and no. A COSC watch will be expected to be within +6-4 sec/day, but to be considered a COSC movement, the movement has to pass COSC testing in the COSC labs.

    And as to your earlier question, the wildest of my mechanicals runs within about 6 sec/day. Most of them are within about 2 sec/day.

    Enjoy!
    Michael Zenner
    Portland, OR USA (GMT -7, sometimes -8)

    Time, Time Time, See what's become of me! -P. Simon

  7. #6
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    Re: Mechanical accuracy

    There is a survey in the Seiko forum of the accuracy of a cheap Seiko movement called the 7s26 or something like that.

    Basically accuracy seems to depend on price (surprise surprise). Cheap watches can vary by 15" or more per day, but often can be regulated to a few seconds. More expensive watches with a decent ETA movement often seem to achieve a few seconds per day. Accuracy will depend on the quality of the components and the amount of effort put into regulating the watch. There seems to be a lot of discussion in the affordables forum of DIY regulation.

  8. #7
    Member lysanderxiii's Avatar
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    Re: Mechanical accuracy

    The 7S26 and 7S36 are the Seiko workhorse autos and are comparable to ETA 2824s, although, I don't think Seiko bothers to fancy them up beyond what ETA would consider standard grade. It's performance is typical of that grade movement which also includes the FHF 96 serie handwinds, and the Miyota 8215 automatics.

    The gain/loss on the wrist depends greatly your habits, and a watch regulated to +2 seconds on one person might lose 10 seconds on someone else's wrist.

  9. #8
    Member Phrooq's Avatar
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    Re: Mechanical accuracy

    I've had a Tag and Rolex in the past, both of which have been COSC certified Chronometers. Accuracy has always been no worse than +2-3 seconds per day, as would be expected when spending that amount of money. I have also purchased a couple of Seikos with the 7S26 movement, and sure enough the accuracy is debatable. I get variations ranging from +5 to +25 seconds per day. This is no good in my opinion, although I have heard some other forum members claiming much higher accuracy from the same movements. (there's a separate thread on this in the Seiko forum). i managed to pick up a vintage hand-winding Omega Seamaster recently and it has an accuracy of +5 seconds per day. Not bad for a 50 year old watch.

    On the other hand, I also have a few Quartz watches, and these are always consistently accurate. My personal recommendation would be to go for a higher end mechanical if you are interested in accuracy, and if you aren't then a Seiko mechanical is great value for money.

  10. #9
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    Re: Mechanical accuracy

    I'd say that accuracy in a mechanical/automatic watch can sometimes depend on luck. My Sinn 657 (with Eta 2824 I believe) was always very accurate for me. Average was +1/+2 seconds per day when worn and +4/+5 seconds on a winder.

    Earlier this month I dropped the watch on my bathroom floor (tile) and in addition to a small ding on the case back I noticed a very interesting thing - the watch now loses about 1.5-2 seconds per day when worn and gains 1.5-2 seconds during the night (dial down) giving me perfect time on average. Gains about 0.25 seconds per day when on a winder.

    Needless to say, I'm pleased with the "upgrade"

  11. #10

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    Re: Mechanical accuracy

    That's a good point. A shock to the watch could also improve the accuracy. You never know.

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