As you have never done that before, and as you do not seem to be confident about doing that, I would advise you have your watch checked and if possible serviced by a watchmaker. It is pretty easy to damage the hairspring of to make a big ugly scratch on the balance cock...

 

Hi,

you are right. It's not worth the risk to try by myself. Speaking about watchmaker, I want to ask you a question about this matter. Some two days ago I have showed the watch (Omega 601 movement from the pictures) to a watchmaker in order to obtain a price for a proper C.L.A. He put it in the vibrograph which showed him some +65 seconds per day. What intrigued me was the fact that he told me that after he CLA which he will peform, the watch will have an accuracy no better than +20 seconds per day and that this accuracy is the one which the watch had it when it was brand new. How can you draw such a conclusion after a test of only 5-10 seconds ? You didn t study a second an article about that movement. You have just looked a few seconds to the movement and tested its accuracy on the vibrograph... Is such an approach plausible? I am asking you, because for me it sounds like a disclaimer.

Best regards,
Cristian.

 

I am not sure your watchmaker went to that conclusion because of the short test he performed on your watch. I would rather think - from what you said and because it makes much more sense - he told you that because of what he know about this caliber.

I do not know the specs for the 600 series - @Archer will certainly know - but telling you not to expect better than 20 secs a day seems carreful. I guess a good watchmaker can do better on 600 movements in good condition or if he can replace parts. But telling you that seems a good policy in order to avoid any disappointment.

 

I understand. Thank you. Maybe my judgement was wrong.

 

Mr. Archer could you help me with the usual accuracy of an Omega 601 movement ? I have posted three pictures at the begining of this thread. In my case the movement looks very good, but I don t know the history of this particular watch. Giving the serial number of my watch, I belive that it is from 1965. Thank you.

 

I think Francois is right in what he's saying. Your watchmaker will know what he can reasonably expect from one of these.

I might be able to help with your understanding. I provide a service document with watches I service and at the end, include the performance figures. Here's an extract of one that is a non chronometer like yours and similar age and construction. In fact it has a lot of common parts to yours.


I check the other three positions as well.


This is an explanation of the graphs and a summary of a +24 hour test.


So, if we take the full wind positions, this watch could run anything from -7.5 seconds to +6.1 seconds per day. Let's call that a variation of 14 seconds. I also say it has a 13 second variation after 24 hours so, in a simple way, this watch has good isochronism (it's not that simple but it suits for this). These graphs are just a point in time so need to be read with some care but these are very good results for a non chronometer.

Realistically, therefore, I can set this watch to run at (say) 0 seconds per day and if I leave it in any position for a day after full wind, it should finish that day somewhere between -7 and + 7 seconds. That's pretty good.

I do a long term (about a week) test after setting it and the idea is to simulate real world usage in varying positions so I can set it to run where I want. This might lead to a mean of +4 seconds with a variation on the test -1 to +9 seconds per day. That's a little better.

But, I don't know exactly how you'll wear it so, you might find it's always running close to the +9 seconds and from the charts above, you can see it runs slowest in 3H (crown high) so you can slightly vary the rate by resting it in that position overnight. It might just be that you wear it and rest it in such a way that it runs +1 second per day and you're very happy anyway.

It is not easy to do this as, if you look at those graphs and how close they all are to 0 seconds per day, I still end up with a variation that seems to be outside what you're hoping for. There is a lot of testing and adjusting involved which all takes time and not everyone wants to do that so if your watchmaker is saying a 20 second variation per day (assuming he means 20 total and not + or - 20) then it's not bad for a 50 year old non chronometer.

There is a lot in this and it's not easy to explain in a short time but I hope it's given you an idea of the challenges your watchmaker faces and why he won't just guarantee a particular rate.

Cheers, Chris

 

Thank you so much for your very detailed answer, Chris. You made some light for me. I didn t know how complicated is to obatin a good accuracy. Unfortunately, the watchmaker wasn t very precise when he told me that the best accuracy can be 20 seconds/day (meaning let say -10/+10 or +20 per day). I think the most important aspect of the accuracy is the final variation after 24 hours, because if my watch has a constant 24h accuracy of let say -20 sec/day, after a week I may lose the train if I don t set the right time every two or three days. Do you know how to regulate that movement (3rd image) ? It doesn t have a ”-/+ scale”. I don t know which side is which. You just push the regulator index ? It looks odd to me giving the screw which is mounted in the regulator index.

Best regards,
Cristian

 

Nice explanation Chris!

Christian, in what Chris explaned, there is the important idea of variation over positions. If you adjust the rate via the regulator, you only change the general rate. So if your watch has a huge variation over 6 positions, the average rate could be 0 (or the rate with dial up position), but your watch can still end at, say, + 25 a day and - 25 another day - that would be a very baddly regulated watch, but you get the idea.

So you can adjust the rate via the regulator, but it will improve the real rate of the watch only if you already have an accurate watch - a well regulated watch over 3-5 or 6 positions. So, first, a service is in order!

 

I always find this graphic helpful to explain positional variances and overall accuracy...here the group size is the Delta (positional variation so the spread of the timing in different positions) and the location of the group is the regulation (how close the average rate is to zero):



Regulation is just moving the group, and adjusting is changing the size of the group. If the group is small but not centered, then using the regulator will get you from the upper right condition to the lower right condition. If the group is large, then you need to focus on making the group smaller, not moving it around.

In any case, the Cal. 601 has the following specs from Omega:

Number of positions tested = 3

Delta at full wind = 25 seconds

Delta at full wind +24 hours = 35 seconds

Average daily rate range =- -1 to +16 seconds

Target average rate = +8 seconds

How well a specific watch will do in meeting or exceeding these specifications depends entirely on the condition of the movement, and the skill of the watchmaker. IMO getting the average rate to be better than 20 seconds per day should be fairly easy, but then again the watchmaker could be under-promising with the intent to over-deliver. Or, he could be a complete hack that only regulates in one position and does not adjusting at all - no way to know, but the old adage that you get what you pay for usually applies.

Cheers, Al

 

First of all, thank you Chris, Francois and Archer for your detailed explanations. I think I am starting to understand some things which are the base of the accuracy. Is ”Average daily rate range” an instrument to tell the accuracy of the watch at any Tn moment in those 24h ? I see that this accuracy is far better than Delta at full wind +24 hours. And now this is really my last question on this thread, because I think I might exaggerated: is target average rate the arithmetic mean of the average daily range from above ?

Best regards,
Cristian

 

The average daily rate is the average of the 3 positions measured on the timing machine at full wind. So the average of those 3 positions can fall between -1 and +16 seconds.