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Accuracy over different timeframes


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I had assumed this would be a common topic of conversation but my searches have not come up with any topics on the subject.

I have had a grand total of 2 mechanical watches. The first (20 ish years ago) was a heuer cerera re issue that I could not really afford but it was beautiful, I did not  know a mechanical could be 20 seconds a day out and it really got on my nerves, luckily the shop agreed to take it back.

in the meantime I bought some military issue seiko's but still lusted after a mechanical watch.

I decided to buy a cheap and cheerful Seiko 5 to see how I felt about having a watch that varied each day before splurging on something more expensive.  I’ve been wearing it for a couple of months and initial timings suggested it was 8-10 seconds a day out. I was enjoying wearing it and decided to test it over a week and it seemed to be about 2 seconds a day out over that time. I did another test yesterday which showed it was out by 0.1 seconds a day which i feel is astonishingly good.

so now I’m in the situation where I find I like using a mechanical watch to tell the time but my head is telling me that accuracy like this is incredibly rare and when I buy a different watch I’ll have something that is nowhere near as good but costing at least ten times more.

so what I want to know is how accurate are mechanical watches over time, eg a week, a month?  Would a COSC certified watch be more likely to do the same thing every day? Eg run 3ish seconds fast a day so over a week be 21 seconds out.  Or would a COSC watch be more likely to be a couple of seconds slow one day, a couple fast the next day so it evens out over a week?

Im more likely to buy something like a Sinn 556 (I love tool type watches) and from what I have heard they are fairly accurate but they are in spec if they are within plus or minus 20 seconds a day so I guess that means they could be out by over 2 minutes in a week.

so basically what is reasonable time keeping of a mechanical watch over a week or month?

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On more budget oriented mechanicals manufacturers tend to have stated tolerances somewhere in the 20-30 sec per day range but actually you'd usually be pretty unlucky to get a watch that's more than about 10 sec out. COSC takes it to 5 secs a day, and yes on that sort of movement you'll tend to find it's more consistent too, so it's predictably out by the same amount. So really you are looking somewhere round 2-5 minutes a month depending on luck and/or spend.

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My most accurate mechanical is a non COSC Tudor Black Bay 36, I very rarely have to touch it other than when the clocks change. I've had two COSC watches that I sent back to get regulated, because they were well out of spec, out of the box new, maybe I was unlucky. I have never bought a Seiko, regardless of price that has been anything less than +15 seconds/24 hours, but because I wear something different most days I don't let it bother me. If accurate daily time keeping is something that bothers you (and it sounds like it does) I'd be looking at a Grand Seiko quartz. Some watches timekeeping will vary on and off the wrist. My Black Bay will lose 1-2seconds/12 hours on my wrist, but gain it back overnight with the watch sitting "crown up". All part of the pleasure of owning mechanical watches. :laughing2dw: 

Lastly. Frowned  upon by some for being homage watches, but any Steinhart I've had has been as near bang on as possible.

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Reasonable? Subjective. 20 seconds per day is very reasonable for mechanical watches that aren't COSC certified. Not reasonable if they are supposed to be. Not reasonable if it's your only watch, not as far as I'm concerned, but for most of us, with dozens of watches, we don't care that much. Since it sounds like you aren't a watch collector like us and likely only wear one watch, I honestly don't recommend a mechanical watch.  I suggest you get a nice quartz piece and be happy with it. Accuracy pretty much guaranteed!

However, if you're willing to spend about $2000 and up, then you can get yourself into something COSC certified that will keep you within a 5 seconds per day range. That said, a good watchmaker can regulate almost any movement to be within at least 10 seconds per day, but why spend that money on something that won't be worth it later? I say take your time, get something COSC certified from an AD, so if issues arise later you've got someone to go back to for warranty repair and servicing.

But again, I still recommend going quartz. Or you can really shell it out for a hybrid quartz mechanical with Seiko and their Spring Drive movement, which is guaranteed to be within something like 1 second per month! But yeah, there you're looking at $5000 and up.

I would have a look at some reasonably priced brands like Christopher Ward. They do COSC stuff at a decent price. Most my watches run within 10 seconds per day, even though I don't care because I don't wear them frequently enough for that to matter. Farer is another great brand to consider. I don't think they produce anything technically COSC, but they do regulate they're movements and tend to use the upper grades of them for guaranteed higher accuracy from the factory.

Oris is another reasonably affordable brand that you can bet will have great out of the box accuracy.

Edited by JayDeep
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Not really as I don’t have any need for a dress watch but it’s a great looking watch and not having to change batteries really appeals. It would be nice to have an excuse to buy a dress watch, I love the implementation of the Cartier solar tank.  

as I said my mechanical watch is ten seconds a day out but it evens out over a week, I don’t mind about daily fluctuations but would love more information about how common this is.  
 

In an ideal world I would love a spring drive but I can’t see them making a tool watch version.

Ops, was trying to quote the citizen response.

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2 minutes ago, No time to tell said:

In an ideal world I would love a spring drive but I can’t see them making a tool watch version.

They already do in a divers watch.

Most of  my autos are far more accurate than the +/- 20 seconds.  With the exception of my Seiko 5,  one of the new models,  which thinking about it, I might see if it can be improved. I have 6 COSC's and they are all staggeringly accurate once up and running. 

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2 hours ago, Perlative Cernometer said:

Although bizarrely microbrand watches with Seiko movements often seem to do better.

Better regulated I would guess, the Seiko's I own have been regulated by yours truly and run between + 1 and the worst one + 10 seconds a day, I really should do that one again.

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24 minutes ago, JayDeep said:

Reasonable? Subjective. 20 seconds per day is very reasonable for mechanical watches that aren't COSC certified. Not reasonable if they are supposed to be. Not reasonable if it's your only watch, not as far as I'm concerned, but for most of us, with dozens of watches, we don't care that much. Since it sounds like you aren't a watch collector like us and likely only wear one watch, I honestly don't recommend a mechanical watch.  I suggest you get a nice quartz piece and be happy with it. Accuracy pretty much guaranteed!

However, if you're willing to spend about $2000 and up, then you can get yourself into something COSC certified that will keep you within a 5 seconds per day range. That said, a good watchmaker can regulate almost any movement to be within at least 10 seconds per day, but why spend that money on something that won't be worth it later? I say take your time, get something COSC certified from an AD, so if issues arise later you've got someone to go back to for warranty repair and servicing.

But again, I still recommend going quartz. Or you can really shell it out for a hybrid quartz mechanical with Seiko and their Spring Drive movement, which is guaranteed to be within something like 1 second per month! But yeah, there you're looking at $5000 and up.

I would have a look at some reasonably priced brands like Christopher Ward. They do COSC stuff at a decent price. Most my watches run within 10 seconds per day, even though I don't care because I don't wear them frequently enough for that to matter. Farer is another great brand to consider. I don't think they produce anything technically COSC, but they do regulate they're movements and tend to use the upper grades of them for guaranteed higher accuracy from the factory.

Oris is another reasonably affordable brand that you can bet will have great out of the box accuracy.

Certina and Mido good cheaper budget offerings with COSC ratings.

https://www.thewatchhut.co.uk/certina/certina-ds8-cosc-watch-c0334511603100-c0334511603100.html?

https://www.midowatches.com/en/multifort-chronometer-1-m0384311106100.html

https://www.midowatches.com/en/baroncelli-chronometer-silicon-gent-m0274081603100.html

https://www.cwsellors.co.uk/products/certina-ds-1-powermatic-80-cosc-c0294081608100-watch-crt-386

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21 minutes ago, No time to tell said:

It would be nice to have an excuse to buy a dress watch, I love the implementation of the Cartier solar tank.

You don't need an excuse. I have a Cartier Tank Solo (auto, not solar) and it wears just as well with t-shirt and jeans as with a suit. Oh, and it averages under +2 s/d and has done for 5 years.

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2 hours ago, Perlative Cernometer said:

Although bizarrely microbrand watches with Seiko movements often seem to do better.

My Steeldive was bang on after a week when I last checked it, for £100 that’s not too shabby.

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For mechanical watch accuracy to a couple of seconds a day, I would either buy COSC certified or a watch cheap enough for you to be happy regulating it to run well on your wrist.

Middle price watches generally aren't super accurate out of the box and I would be scared to remove the back in case I ruined the movement.

 

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