All you wanted to know about COSC Certification

[RolexDivers]

A great article --

http://people.timezone.com/library/w...33384647656250

[NYC6]

Im surprised by two things right off the bat
1- Very small % of mechanicals fail
2-Quartz has a higher failure rate(% wise) than mechanicals

[wantonebad]

Really? He spilled his guts after some Merlot and Pinot Noir? Shinnanigans!

[yakmeister]

very interesting read.

[withthesword]

it's actually not so suprising that more quartz fails than mechanical, since the tolerances for quartz are much much tighter in terms of accuracy. they don't just want 99.996% accurate, they want like 99.9999999 etc. not too far fetched considering how accurate regular quartz movements are already.

[NYC6]

Are the COSC accuracy tolerances tighter for quartz than mechanicals or do they use the same parameters?

Just read it, quartz are expected to stay within 7/100ths of a sec/day. You're right.

[padi56]

Today the Swiss COSC is little more than pure marketing as with very careful regulation most mechanical movements made today all brands could pass this test.And with movement parts mostly machine and highly robotised made today by the high volume manufactures.So in theory when assembled they should all be the same so to pass the COSC test with very little fail fate, a Swiss chronometer today is not the holy grail of watchmaking.And as for the quartz well the Japanese chronometer standard plus for mechanical is too a higher standard than the Swiss standard chronometer.

[Kinnakeet]

I actually have this article stored in my documents- its highly entertaining and informative!

[NYC6]

Originally Posted by padi56

Today the Swiss COSC is little more than pure marketing as with very careful regulation most mechanical movements made today all brands could pass this test.And with movement parts mostly machine and highly robotised made today by the high volume manufactures.So in theory when assembled they should all be the same so to pass the COSC test with very little fail fate, a Swiss chronometer today is not the holy grail of watchmaking.And as for the quartz well the Japanese chronometer standard plus for mechanical is too a higher standard than the Swiss standard chronometer.

Not that Im doubting you but it seems to me there are more machanical watches on 'the streets' today that dont meet COSC standards and more Rolexes that do, over time anyway. Do you think so?

[SLRdude]

It's a very good read, although it is 11 years old.

Some things have changed since and now Quartz rules are so tight that Breitling is about the only one that bothers with it.

[padi56]

Originally Posted by NYC6

Not that Im doubting you but it seems to me there are more machanical watches on 'the streets' today that dont meet COSC standards and more Rolexes that do, over time anyway. Do you think so?

Quite true but first lets not forget why the COSC was first formed and Rolex is the largest brand to have watches tested there, so large Rolex have there own special machine there the bare movements are loaded in to magazines many at a time and wound by the machine.The COSC test is now quite antiquated as only bare uncased movement is tested. Now take the European Din standard and the Japanese equivalent for mechanical movements is to a higher standard than the Swiss COSC and both institutions test all the movements in the case thats going to be with the watch for the rest of its life.

And before the Swiss COSC was formed as we all know it today, there were then the Observatory testing competitions to a much higher standard than todays watered down COSC test Now during the entire 23 years of testing, 5093 wristwatches were submitted for this certification, and only 3253 were passed, about 64%.Today the first time pass rate at the COSC is around 90-94% and most movements today are mass produced so in theory they should be all the same so quite easy to pass todays test and many many millions have been tested there by Rolex plus the many others.Now in those early days of Observatory testing just a few manufacturers participated, and only Omega and Patek did so every year. The others were: Rolex, Zenith, Longines, Movado, Vacheron & Constantin, Ulysse Nardin, Cyma and Favre-Leuba, along with numerous independent professional watchmakers.Now that was until the brand Seiko come on the scene and started to wipe the floor with the Swiss mechanical watch industry.Only 2 brand in the + 23 years of the competitions submitted movements of serial production for retail sale(Seiko and GP).All other brands were specially made movements just for the competition,and it was ended by the Swiss in the early 1970s after two straight wins by the Japanese straight off the production line Seiko Grand,shortly after 1973 the Swiss COSC was formed..

It is most important to remember that a "COSC certified chronometer" is not the Holy Grail of watchmaking. With the high quality of modern day robotised manufacturing, this test is not that important in reality. As today most decent modern watches from all countries even some from China like the Seagull movements, when adequately adjusted, should be able to match the performance specified by the Swiss COSC.

And chronometer certificate is not a guarantee of future accuracy only a certification of the bare uncased movement tested at the COSC at the time of testing. Rolex will try with re-regulation to keep movement to spec and regulate at normal 5-7 year service.But many watch movements that have been certified can get out of adjustment and perform quite poorly that's a simple fact of being mechanical. Movements that were not certified could still exceed the COSC standards with just simple regulation.Many of the manufacturers today may have simply chosen to bypass the expense of the certification process its quite expensive to test every single movement. And with all movements today accuracy is only as good as what the movement has been regulated too.

The term "Superlative Chronometer" is a now trademark of Rolex, the addition of the word "Superlative" in front of the official designation of Chronometer is merely a Rolex marketing angle to give a more distinguished sound to the chronometer status of their products . As all watches that have earned the privilege of bearing the official Swiss designation of "Chronometer" have to meet the exact same C.O.S.C. standards for any movement of Rolex size. Any words added before or after the official designation of "Chronometer" are merely marketing.

When thinking of accuracy its very important to remember that even when a mechanical watch is allowed to vary by COSC standards a AVERAGE +6/-4 seconds per day, that does not mean it will consistently vary by that high or low amount each day. Mechanical movements that self regulate say by resting in different positions over night its quite rare for this to happen.All Mechanical watches are noticably affected by the gravitational pull of the Earth, it only takes a performance distortion of 1/1000th of a percent for a mechanical watch movement to be one second less accurate in a day. So to get any mechanical watch to self regulate with zero tolerence is IMHO something thats very rare maybe one it quite a few thousand.

How they regulate on a machine watchmaker and will make fine adjustments to the beat rate timing rate amplitude and try and get as close to ideal as possible. Now this is achieved by turning the Microstella adjustment screws and nuts on the balance wheel.The two smaller Microstella screws make adjustments of one second for each turn, and the larger Microstella screws nuts two seconds for one turn.


On the COSC test the movement could vary by as much as 10 seconds in any 24 hour period in the first 10 days of testing and still pass the test.

[NYC6]

informative post

[kleno]

Interesting, must say...