what is the meaning of C.O.S.C. specified a daily rate of -4/+6 sec per day?

[ROLEX]

Hi everyone, I'm new here. Can any watch expert enlighten me what is the meaning of -4/+6 sec per day?
Is it means that if you are having a fast watch the most it will be fast by 6 sec per day,and if you are having a slow watch it will not slow more than 4 sec per day (i.e: 4sec x 30days = not slow more than 120secs per mth)?
Or
The same watch may go fast or slow each day and after plus and minus at the end of the month it will still very accurate?
I bought a brand new Datejust 116200 6mths ago, everyday fast 3 to 4 sec (I monitor closely everyday ,it always fast)
Last month I bought a brand new Explorer 2, everyday slow 3 to 4 sec (one mth slow nearly 2 mins).
I understand that different position we place the watch will make it slow or fast but even I place it face up (like those in the show case) try to make it run faster but it still slow by few secs.
I can't express myself well in English. Hope you understand what I means. Thanks.

[Hary]

Hi everyone, I'm new here. Can any watch expert enlighten me what is the meaning of -4/+6 sec per day?
Is it means that if you are having a fast watch the most it will be fast by 6 sec per day,and if you are having a slow watch it will not slow more than 4 sec per day (i.e: 4sec x 30days = not slow more than 120secs per mth)?

This is the right answer.

Don't worry about the accuracy as long as they are within tolerable range (eg. within COSC range). For new watches, let it run for a while, same as car, watch movement needs to be 'run in'. My Exp I since day 1 runs +7sec/day, actually out of spec, but I didn't bother to bring it for adjustment. Obviously no difference after run in. But most of my watches 'stabilize' after certain period of time.

[shuseido]

Hary is right. Let the new watch "run" for a period.

My PO having the same problem. It was -4 per day when new, after 3mths and till now (15mths old), constantly run +2 per day. Quite happy with this result. Dun worry too much.

[benhur]

sori but 'run-in' meaning wat? wear te watch everyday for 1mth? or 2mths?

[ROLEX]

Thanks Hary & Shuseido

Am I right to say that after run in for a period, the machines/gears/oil inside the watch will go smooth,even and stable? But if the slow watch will be back to normal (smooth gears will go faster), how about the fast watch? will go faster? (i.e: instead of + 4 sec become + 6sec per day?)
When we buy new watches, is it better to have a fast watch or slow watch before run in? Sorry to ask so much questions. Thanks again.

[winzchee]

Am I right to say that after run in for a period, the machines/gears/oil inside the watch will go smooth,even and stable? But if the slow watch will be back to normal (smooth gears will go faster), how about the fast watch? will go faster? (i.e: instead of + 4 sec become + 6sec per day?)
When we buy new watches, is it better to have a fast watch or slow watch before run in? Sorry to ask so much questions. Thanks again.

Hi Rolex, it is tolerable if your watch is running about +- 6 seconds per 24 hours. Some of my watches are going about +4 secs per day and others are slower about 3 seconds per day. But overall as long not too fast or too slow over a short period of time, then it should be quite okay. Even if you have to regulate your watch, my advice is better let the authorised service centre do it. I've sent in my BALL Engineer Hydrocarbon Madcow for regulating recently when it was going fast about 12 seconds per day and so far it is running about -2 seconds per day right now. Best Regards & Cheers.

[ROLEX]

Thanks

Thanks winzchee. For COSC standard it will be ok for a watch which -4/+6 sec per day. But if +6 sec per day for one month, it will be fast around 3mins. Can't imagine those automatic watches which not under COSC standard.
Anyway not eveyone watch is having the same timing. Some even adjust fast or slow by 10mins (so they can report off from work early or prevent getting late to work)

[speedy27]

my sub is faster by 5 or even 7 mins in 1 week, this is very adnormal...
i bought 2nd hand from a shop and have 1yr warranty by them. if i send it back to them is it safe? will they send to rolex service centre for servicing?

[philinves]

Am I right to say that after run in for a period, the machines/gears/oil inside the watch will go smooth,even and stable? But if the slow watch will be back to normal (smooth gears will go faster), how about the fast watch? will go faster? (i.e: instead of + 4 sec become + 6sec per day?)
When we buy new watches, is it better to have a fast watch or slow watch before run in? Sorry to ask so much questions. Thanks again.

My friend a rolex technician says it's better to have a faster watch...and say
it will compensate over the years. Don't know what it means though.

[ROLEX]

COSC = warranty period?

my sub is faster by 5 or even 7 mins in 1 week, this is very adnormal...
i bought 2nd hand from a shop and have 1yr warranty by them. if i send it back to them is it safe? will they send to rolex service centre for servicing?

I believed the shop also have no time to check the accuracy of every watches they brought. That's why they will give the buyer 1yr warranty. If follow COSC standard, one week (7x6secs) will not be more then 42 secs. Only vintage watches will be 7mins or more per week and will not be accurate at all.(I read from PASSION Web page)

[ROLEX]

Thanks Philinves. I also heard from friends said that for new watches, fast watches is better than slow watches. Maybe after certain years, the gears/parts will become loose due to wear & tear and the timing will be slow down a bit.
Wonder If a watch is 'certifed chronometer' is there any time limit/warranty for such standard? (i.e:we buy a new watch which is COSC certifed, but is it forever or after few years the watch may not be accurate and we can't call it Chronometer watch anymore?)

[9166]

I got two subs, one runs 2sec slower per day and the other goes 5 sec fast per day. Both 2 weeks old. iF like that, 1 year the watch will be faster by half hour... Does this mean I have to keep adjusting all the time?

[ROLEX]

Don't Worry About That Few Secs Per Day

We can't compare the accuracy of mechanical watches with digital/battery operated watches. Automatic watches, fast/slow few secs per day is consider good liao. For Chronometer watches such as ROLEX, fast/slow 4 to 6 secs per day is normal (I also worried before). That's why someone said: "If you need to be punctual to work, wear a CASIO. If you no need to be punctual to work,wear a ROLEX". No wonder why so many bosses wearing Rolex. From what I know for mechanical watch, the SEIKO 'SPRING DRIVE' is the most accurate +/- 1 sec per day.

[jSkywalker]

I'm for one quite particular about accuracy of mechanical watch, my personal tolerance is -2 to +3. Anything more than that I'll try to regulate it, if i can open the case. I'll do the adjustment till I'm happy. I did that on my Seiko 7S26 diver's watch, from +20 to +3 per day. Took me a few weeks because I don't have a machine... Rolex is another problem because I don't even have a case opener... even if I have, the adjustment is very complicated and if not careful can damage the hairspring. Hence, the way I deal with Rolex is to let them rest at different position during the night and see what's the best accuaracy I can get at different position.

So far the worst Rolex I had is +5 and the best one is on the dot, after I find the best resting position for the watch.

I also realised that mechanical watches normally tend to run fast as it age, sometimes due to its mechanism or even sometimes being magnetised, maybe only the milgauss can be spared.

I had tried to bring the +5 watch to RSC for calibration, they checked but they said they will not do anything as long as it is within specs.... think they can do better with their customer service...