The first check made is of the shock protection jewels and for this calibre, the shock protection system is Incabloc. In the initial review, it was noted that the amplitude was poor in the dial up position where the balance is running on the end stone in the cock. Most people leave their watch in dial up overnight so this tends to be the pivot that is worn before the one on the dial side. Looking at the end stone, there is a clear indentation caused by running the movement dry in the past and this was not spotted by the last watchmaker to open this watch – this sort of repair can be very expensive depending on the extent of the issue and is one reason that I advise regular servicing of vintage watches. This area should be flat and if the jewel is damaged like this, then the pivot end is very likely to be flattened as well. Fortunately, new Inca jewels are available but the success of the polishing will depend on how damaged the pivot is.
The other jewel is fine but this upper pivot end will require polishing to return the best performance. Initially, the balance and hairspring is removed from the movement and this is the view from above – the hairspring is a nice shape and is of the Breguet overcoil design. It is this upper pivot that will require polishing.
The other side has the roller table with impulse jewel and under the microscope, I can see that this pivot end is fine but can’t capture it well for a photo.
To polish the pivot, I can use the Jacot tool.
This takes ten minutes to set up and I need to strip the spring and roller table from the balance before polishing and then replace them. It’s easier when only the ends need to be polished to use this Bergeon tool that can be used on the balance without further strip down. It’s a small tool at about 50 mm long and with a polishing jewel in one end but it only works if the flattening of the pivot is small. If it has been left running dry for a long time, then the Jacot tool is needed and, possibly, a new staff.
I show the effects of the polishing in more detail in this page. Although it’s for a different watch, the logic is the same. After polishing the pivot, the balance is re-assembled, the cap jewels buffed, oiled and fitted so that just the balance assembly is on the main plate. This shows the oil in the jewel.
And here is the balance only on the plate so that the concentricity and flatness of the spring may be checked and adjusted. In this case, with a very small adjustment, all is fine.
The centering of the hairspring in the regulator pins and the pin gap is checked although for this movement, no adjustments were required.
Now that the review is complete, the assembly can start.