What even is accuracy? What makes a movement accurate? My work on cheap "inaccurate" movements. They can be quite accurate.

[Birbdad]

I'm only making this post because I'm now convinced it's not a fluke. I've only repaired/serviced 6 movements now. All of them either 7s26's or nh36's with the exception of a seiko 7006a. When i dove into hairspring fine tuning for adjusting the regulator pins and working with the etachron system and of course trying to do a PERFECT lubrication and cleaning, the first watch i REALLY put in the work on to try and get my delta as small as possible over the course of almost two weeks never deviated more than 2 seconds a day of on the wrist wearing. I've been told how inaccurate this movement is since i got into this so I figured i just won the manufacturing tolerance lottery. This was after timing on my wrist and then changing the rate to reflect that deviation and just checking every day at the same time.  Even months later that watch is STILL running with average deviation between 0 and 1 second a day.
 

I decided to fine tune the hairspring and regulator pins again on my latest watch. A brand new nh36 that i cleaned and serviced day one as the factory oiling and adjustment was pretty awful. 
This is now 4 days of deviation. Less than 2 seconds.
 

At the very least I guess I just want to say people should not sleep on these cheap japanese movements. I think they are far more accurate than people give them credit for. Seiko just doesn't put much effort into adjusting and regulating them at the factory and on stand alone NH3X movements the factory oiling can be all over the place, literally. That or i hit the manufacturing tolerance lottery twice. 

My question is, If it's possible to get accuracy this good out of a 30 dollar movement with just a little fine tuning and a good lubrication job outside of decorating and less plastic, what is so great about a cosc movement that costs 100 times the price? Do they just stay accurate for longer? What even makes a movement accurate and another not?

Edited April 29, 2023 by Birbdad

[Nucejoe]

Accuracy refers to the STATE of closeness to a standard, expected or given value.

 Within one second was your watch accurate, had it shown 10 seconds off  , your watch would have still  been ACCURATE ,  its also acuurate  if its within 8 or 17  seconds next time you check .

ACCURACY IS ABOUT THE  CLOSENESS OF AN ACTUAL VALUE TO THE TARGET.  obciously one second is more acuurate than ten seconds, but says nothing about its precision.

COSC  certififies how PRECISE a watch is. The next question is " what is precision" .

 Increse the number of measurements to hundered or multiples of hundereds. your watch is " PRECISE "  if it showed accurate time in 98 or 95 measurements out of hundered,  so precision is about how  frequent/ reliable  is its  accuracy.  

An example to show the significance of precision.

One is  as good/ alive as  the rate of hit when designing/making a anti fighter jet missile. In friendliest terms , at his funeral,  an incompetent engineer never knows  how imprecise the missle he made was.

Just kidding matey. 

 

 

Edited April 29, 2023 by Nucejoe

[Klassiker]

6 hours ago, Birbdad said:

outside of decorating and less plastic, what is so great about a cosc movement that costs 100 times the price?

COSC or any other accuracy test certificate doesn't specify the materials to be used in the movement. Nor does it have anything to say about the standard of finishing. It is a test to determine the timekeeping accuracy of a movement in different positions, at different temperatures and at different power levels (mainspring wind). Interestingly, COSC doesn't say anything about how long the movement will retain its accuracy, nor even if the same accuracy will be reproduced when the movement is cased up.

You can have a can have a watch which is very accurate when the owner wears it (but maybe not if someone else does, or if left to run down on a cold windowsill) which will perform terribly in COSC testing. The other way around is much more unlikely.

What you have probably managed to with your watches is to average out the errors under a controlled and unvarying set of service conditions, i.e. on your wrist, following your daily routine. You have done it very well indeed, so congratulations.

[Birbdad]

1 minute ago, Klassiker said:

COSC or any other accuracy test certificate doesn't specify the materials to be used in the movement. Nor does it have anything to say about the standard of finishing. It is a test to determine the timekeeping accuracy of a movement in different positions, at different temperatures and at different power levels (mainspring wind). Interestingly, COSC doesn't say anything about how long the movement will retain its accuracy, nor even if the same accuracy will be reproduced when the movement is cased up.

You can have a can have a watch which is very accurate when the owner wears it (but maybe not if someone else does, or if left to run down on a cold windowsill) which will perform terribly in COSC testing. The other way around is much more unlikely.

What you have probably managed to with your watches is to average out the errors under a controlled and unvarying set of service conditions, i.e. on your wrist, following your daily routine. You have done it very well indeed, so congratulations.

Yeah i guess that makes sense. So i supposed a less accurate movement can be made as accurate as possible then tailored to your daily routine and run phenomenal while an "accurate" movement would be far more accurate on a desk or somebody elses wrist as well as your own and could probably achieve the same accuracy if you tailor it to your routine but would be more accurate in other conditions than the cheap movement. That does make sense.

I'm just astonished how well these things keep time if you put the work in while every time i asked about fine tuning and adjusting it all i ever heard was "Don't bother, those movements aren't accurate enough to even worry about adjusting the etachron or fine tuning the hairspring to a perfect center of the regulator pins etc etc".

[Klassiker]

13 minutes ago, Birbdad said:

I'm just astonished how well these things keep time if you put the work in

True, but if you worked for Seiko and they paid you a living wage, they would have to charge their customers a lot more for the watches, and would probably sell a lot less. It would be counterproductive in business terms.

16 minutes ago, Birbdad said:

Don't bother

There's always something to be learned by trying it for yourself.

[Nucejoe]

2 hours ago, Birbdad said:

I'm just astonished how well these things keep time if you put the work in while every time i asked about fine tuning and adjusting it all i ever heard was "Don't bother, those movements aren't accurate enough to even worry about adjusting the etachron or fine tuning the 

They r telling you the truth.

Seiko actually regulates 7S26  more accurate than you do, but no skilled masterwatchmaker spends time  adjusting  it to several positions, because they know they  can't expect high precision out of its escapement as its a low grade one. 

Did you regulate your watch to ONE second accuracy or adjusted its escapement? 

High grade materiasl plus plenty of high skilled labour goes into making and adjusting a high grade escapement.