I was servicing this Smiths Everest and when built, the positional performance was very poor.
As discussed here, I usually test all mechanical watches in six positions and the watch performance can be improved with various methods, some of which are shown below.
I’d already centralised the hairspring in the regulator pins although the pin gap looks a little large.
And adjusted the hairspring to be concentric.
It’s the complete balance that has the most effect on positional variation and usually, this set-up would give good performance with all other things being equal.
Here are the results of the first test. The small pictures along the lower show six typical positions and the left large picture is the fastest with the right being the slowest.
This is a sixty second variation over six positions and I’d hope to be able to halve that even with this Smiths calibre that is not the most expensive.
There’s another obvious issue and that is the dial up (CH) and dial down (CB) are very different. First thing is to equalise these two which is mainly due to the parallelism of the regulator pins.
As all the vertical positions are slower than horizontal, the regulator pin gap is too large and as the vertical positions have a large variation, the poise of the balance is questionable.
As the balance poise is to be checked, first thing is to remove the balance and spring from the cock.
Then remove the hairspring and here is the underside of the balance showing the various poise work made at the factory (all the small circular cuts).
The balance is checked on the poising tool and with slight additional adjustment, it’s poised better than it was. This is a trial and error process because each heavy point means removing a little material from the underside of the balance so, can take a little time.
As the hairspring is off the balance, it’s checked and slightly adjusted so that mounted on the cock without the balance it fits correctly in the regulator and is central to the jewel. At this point, the regulator pin gap is closed a little to try and improve the difference between horizontal and vertical positions.
The spring is removed from the cock, pressed onto the balance with the staking set and then the whole assembly is refitted to the watch. Concentricity of the spring, centering of the spring in the pins are checked and the results of the next test are as below.
Total six position variation has been halved to 30 seconds, dial up is within a few seconds of dial down, all vertical positions are much closer than in the original image.
This is a good result for this Smiths and could possibly be improved further but this is a good point to stop as it’s within any reasonable specification. For a higher quality watch this variation can usually be reduced even with vintage movements.