Balance staff change on an Omega (Lemania) 5600
This was the first balance staff change I did some time ago but the large scale makes it easy to see. It’s a Lemania based Omega stopwatch and I bought it not running with some parts in an attached container… never a good sign. There is no shock protection on these balances and one fault is clearly that the balance staff is broken.
After stripping the movement, I remove the balance and then the hairspring from the balance, leaving the balance and roller table. I separate these with this tool.
This leaves just the balance and staff and now, the issue is clear – one pivot is broken and the other bent.
Some people punch the balance staffs out but that is poor practice so, into the lathe to remove the shoulder.
Just prior to finishing the removal of the shoulder.
Shoulder removed and the staff, remnant of the shoulder and undamaged balance wheel shown.
The new staff gets trial fitted in the cock and plate before fitting to the wheel.
The new balance staff gets rivetted onto the balance with a staking set. The three lines shown on the balance here were added by some previous watchmaker to help in adjusting beat error – not good practice either.
The staff is fitted but checking in the truing calipers, it is not perfectly true when rotated so, that’s corrected to achieve the following with the wheel rotated 180 degrees between each picture.
The roller table gets refitted with the staking set.
And the balance assembly gets poised on the poising tool. Another small drill cut in the lower of the wheel is needed to get the poise correct.
The hairspring is pressed back onto the staff with the staking set. The red dots are added so that the lift angle used for testing can be determined and are removed later.
The balance and spring refitted to the plate and cock in order to adjust the spring to be concentric, flat and centered in the regulator pins.
And shown running in the final built movement.
The degree of difficulty increases as the caliber size decreases but the basic process followed is the same.
The finished watch.