COSC Question

[mretzloff]

I posted about my Sub running fast a few days ago. I'm a little confused on the COSC standards.

The -4/+6 thing...Does that mean a COSC watch can never be 6 seconds ahead? Or does that mean a COSC watch cannot gain more than 6 seconds a day (42 seconds a week)?

Thanks for any help.

[Art161]

It means not losing more than 4 seconds per day nor gaining more than 6 seconds per day.

[Goodwatch]

It means that to receive a COSC qualification, the movements (only the bare movements, even stripped from their date function are tested) must adhere to that standard. You must realise that these are laboratory conditions. As soon as the movements are put back into their case and shipped out, anything can happen. But don't worry about this, the way of the mechanical movement is the way of Zen. It is a sheer wonder that those little machines achieve this at all! If you want dead-on accuracy, buy a watch that is governed by one of those time signal transmitters. A soul-less wonder

[mike]

Frans is spot on. COSC is more a marketing thing than anything else. About any good movement can be adjusted to COSC specs. A better indication is how the watch preforms on your wrist. Should it need adjustment, it's a simple process for a skilled watchmaker.

[mretzloff]

Originally Posted by mike

Should it need adjustment, it's a simple process for a skilled watchmaker.

If I let my AD do it, should I make sure he's certified by Rolex?

[mretzloff]

Originally Posted by Art161

It means not losing more than 4 seconds per day nor gaining more than 6 seconds per day.

So 42 seconds a week is fine then? That seems a bit much.

[Art161]

Originally Posted by mretzloff

So 42 seconds a week is fine then? That seems a bit much.

I don't think it is fine, but it is within COSC specs. RSC should be able to adjust it to be much more accurate. Be sure to tell them how much time it gains when you wear it, and whether you wear it 24/7 or take it off at night. How it runs on your wrist is not necessarily how it runs on their timing machine.

[mretzloff]

Originally Posted by Art161

I don't think it is fine, but it is within COSC specs. RSC should be able to adjust it to be much more accurate. Be sure to tell them how much time it gains when you wear it, and whether you wear it 24/7 or take it off at night. How it runs on your wrist is not necessarily how it runs on their timing machine.

If my AD is certified by Rolex, should I let him do it?

Thanks for the help so far.

[Art161]

Originally Posted by mretzloff

If my AD is certified by Rolex, should I let him do it?

Thanks for the help so far.

I was trying to ignore your post about that. Some ADs have a competent watchmaker and some do not. Rolex certification would be nice, but I don't know that all Rolex certified watchmakers are necessarily competent. There is potential for problems any time your watch is opened. There are some disaster stories on TRF about RSC, particularly NY. I have written something in response to your question, but have probably not answered it definitively. The only people who service my Rolexes are SF RSC. That's easy for me, since they are only a short walk away.

[chevycorvette]

how long u been wearing ur watch?

i wear my explorer 2 daily. and it ran 30 seconds faster in 1 month. so it is around 1 second a day.

my gmt 2-c is sitting in my drawer and i just wore it a few time. so the accuracy of my gmt 2-c is terrible.

[mretzloff]

Originally Posted by Art161

I was trying to ignore your post about that. Some ADs have a competent watchmaker and some do not. Rolex certification would be nice, but I don't know that all Rolex certified watchmakers are necessarily competent. There is potential for problems any time your watch is opened. There are some disaster stories on TRF about RSC, particularly NY. I have written something in response to your question, but have probably not answered it definitively. The only people who service my Rolexes are SF RSC. That's easy for me, since they are only a short walk away.

Sorry to keeping going, but would you allow your AD to touch your watch (if RSC SF wasn't there)?

[scottschoe]

Originally Posted by mretzloff

Sorry to keeping going, but would you allow your AD to touch your watch (if RSC SF wasn't there)?

Just send it into RSC if your AD is worrying you.

[Z-Sub]

Originally Posted by Art161

It means not losing more than 4 seconds per day nor gaining more than 6 seconds per day.

rolex has more stringent standard and if it is more than 3 seconds deviation a day they will adjust it for free.

[Art161]

Originally Posted by mretzloff

Sorry to keeping going, but would you allow your AD to touch your watch (if RSC SF wasn't there)?

I don't know. I have enough reality to think about, and try not to deal with hypothetical questions.

[mretzloff]

Originally Posted by Z-Sub

rolex has more stringent standard and if it is more than 3 seconds deviation a day they will adjust it for free.

Out of curiosity, how much would it cost if it was less than 3 seconds? Would the warranty cover that?

[Nitibus]

Originally Posted by Goodwatch

It means that to receive a COSC qualification, the movements (only the bare movements, even stripped from their date function are tested) must adhere to that standard. You must realise that these are laboratory conditions. As soon as the movements are put back into their case and shipped out, anything can happen. But don't worry about this, the way of the mechanical movement is the way of Zen. It is a sheer wonder that those little machines achieve this at all! If you want dead-on accuracy, buy a watch that is governed by one of those time signal transmitters. A soul-less wonder

I test all my watches by my atomic watch ( AKA soul-less wonder ) My new sub is less then 3 seconds off per day. The closest watch I had before that was off 11 seconds a day. I'm still amazed.

[Trurolexer]

Originally Posted by mike

Frans is spot on. COSC is more a marketing thing than anything else. About any good movement can be adjusted to COSC specs. A better indication is how the watch preforms on your wrist. Should it need adjustment, it's a simple process for a skilled watchmaker.

X2!!!

[mike]

Originally Posted by mretzloff

If I let my AD do it, should I make sure he's certified by Rolex?

Rolex no longer "certifies" watchmakers. There was a time when that was so, but now it's Rolex trained. If you trust your AD and he/she has a trained watch repairman on site (or available) AND has the proper pressure equiment to check the watch afterwards --sure. Regulating one isn't difficult if the watch repairman has the proper equiment and takes into account your wearing habits.

[acce1999]

It's more complicated than that. The -4 to +6 is a combined interval based on the COSC test. It is about a mean daily rate (variation) over a series of tests (positions and temperatures). Check out http://www.cosc.ch for more info.

In real life this means that a COSC watch, that is tested over 16 days, is allowed to deviate as much as -4 * 16 seconds to +6 * 16 seconds over the period. Daily variation can therefore be much more. A COSC can deviate even 12 seconds during one day, as long as it is within the average - 4 to + 6 second per day over the period.

So, a Rolex CAN loose more than 4 seconds per day, or gain more than 6 seconds per day, and still be within COSC limits, since the test is measured over 16 days.

What's more important is how much difference there is between the days, if it is always going +10 seconds, or if it goes +10 s one day, and then -4 the next (the latter being much more worse).

I hope this info adds something to the discussion.

Best,

A

[padi56]

Now Frans and Mike are 100% correct no mechanical watch is going to be 100% spot on, close yes, but spot on no.The most important thing with any mechanical watch is consistency,if a watch was say a minute fast every day then that watch is still very accurate and all thats needed is regulation to bring it back to COSC spec.Fact Most mechanical movements made today with careful regulation could meet the COSC standards.But it takes time to regulate a movement and in todays market time costs money.Now Rolex movements are all built to be chronometers others have to be adjusted to meet the standards and might need adjusting a few time a year.
Take a 60$ Alpha chrono I have after careful adjusting by my watchmaker friend has been running now for several years well within the COSC standard but has been re-adjusted several times.But have a few Rolex from the 60s and 70s still running to COSC spec for many many years without any regulation.

But with any mechanical watch if it runs perfect on your wrist don't necessarily mean it will run the same on someone else's wrist.Remember its mechanical and like cars there will slight differences in the same models.Now in 24 hours, the escapement of a mechanical watch pushes the gears 432,000 times. Since a day has 86,400 seconds, even a watch that runs five minutes fast or slow each day has an accuracy of over 99.6 percent! A finer mechanical watch that gains or loses about nine seconds a day or about a minute a week has a breathtaking precision of over 99.99 per cent. This is very high precision, given the fact that the movement is constantly affected by the earth's gravity, metal expansion and contraction, temperature variations, subtle changes in lubrication and friction, shocks, and so on.The fact is that no mechanical watch made will keep perfect time, very close yes but perfect no.If you want spot on perfect then its one of the radio controlled or quartz hybrids watches.


And regarding IMHO today the COSC test is just a pure marketing ploy this is a direct quote from Watchbore estimates that at least 15,000 Rolex movements failed in 2001-2. According to Rolex, the rejects are re-regulated or fixed, and sent back to COSC until they pass.Rolex Quote. "We don’t use COSC to tell us how good our movements are," said a source deep inside the Wilsdorf Rolex foundation. "We test them ourselves. All we want is the chronometer certification, it’s only for marketing."... I rest my case the COSC test now just a pure marketing ploy. .

The Rolex ladies Datejust with cal 2235 is the most consistently precise and accurate movement tested by COSC.But don't forget that Rolex is the largest movement supplier for the COSC test.With the ETA 2892 Rolex Cal 3035 and the Valjoux 7750 given excellent results.The most precise machine tools are only viable in high-volume production watches.While its possible to get chronometer standards to hand crafted watches ,its very time consuming and needs a lot of adjustment and failures are quite high making more expense.But your massed produced machine made movements are far more consistent in getting though the COSC test simply because they should be all the same.

But looking at the other sign of the coin today any modern day wristwatch chronometers are, by the almost 300 year old 18Th century navigational standards imposed on John Harrison H4 watch,quite laughably inaccurate even by todays standards.How about just 5 seconds slow after 63 days at sea,not bad for a almost 300 year old watch.When you think he had very primitive tools by todays standards all hand made no computer aided help now thats a real watchmaker.

Originally Posted by mretzloff

Sorry to keeping going, but would you allow your AD to touch your watch (if RSC SF wasn't there)?

Fact any competent watchmaker could regulate or service
a Rolex watch.Its not rocket science,the problem lies in getting parts Rolex USA has such a strangle hold of its parts supply thats the problem.There are many independents that are just as good as the RSC in some cases better and more helpful to the customer needs.

[BigHat]

Originally Posted by padi56

And regarding IMHO today the COSC test is just a pure marketing ploy this is a direct quote from Watchbore estimates that at least 15,000 Rolex movements failed in 2001-2. According to Rolex, the rejects are re-regulated or fixed, and sent back to COSC until they pass.Rolex Quote. "We don’t use COSC to tell us how good our movements are," said a source deep inside the Wilsdorf Rolex foundation. "We test them ourselves. All we want is the chronometer certification, it’s only for marketing."... I rest my case the COSC test now just a pure marketing ploy. .

The Rolex ladies Datejust with cal 2235 is the most consistently precise and accurate movement tested by COSC.But don't forget that Rolex is the largest movement supplier for the COSC test.With the ETA 2892 Rolex Cal 3035 and the Valjoux 7750 given excellent results.The most precise machine tools are only viable in high-volume production watches.While its possible to get chronometer standards to hand crafted watches ,its very time consuming and needs a lot of adjustment and failures are quite high making more expense.But your massed produced machine made movements are far more consistent in getting though the COSC test simply because they should be all the same.

But looking at the other sign of the coin today any modern day wristwatch chronometers are, by the almost 300 year old 18Th century navigational standards imposed on John Harrison H4 watch,quite laughably inaccurate even by todays standards.How about just 5 seconds slow after 63 days at sea,not bad for a almost 300 year old watch.When you think he had very primitive tools by todays standards all hand made no computer aided help now thats a real watchmaker.

I agree completely with this post. Yes, in Rolex's own words the 2235 watches watch movement is a standout. I posted this six months ago and it seemed to rub many of the members here the wrong way.

[Tools]

Originally Posted by mretzloff

Sorry to keeping going, but would you allow your AD to touch your watch (if RSC SF wasn't there)?

To answer this question....Yes.

I know that my AD has a Rolex trained watchmaker on staff. I have no issues with leaving any watch I own with him for regulation.

[CH & USA]

I'm going to test my brand new DJ... I "guesstimated" that it was consistently gaining ~10sec/day.