This rather lovely Bulova came in with a broken balance, however a new complete balance was included for fitting which made things much easier. The watch as a hole was in very good condition for the age as most of these end up rather battered, the new balance was not going to be enough as even when fitted with a new one the timing was not right. A service and new glass should see things right, along they way we shall see what is causing the timing issues.
The casing and case back on this watch, like many military watches, has a grey to dark grey finish. This finish is created by a chemical process known as " Parkerizing " and this helps to prevent corrosion caused from moisture , kind of a good idea in a tool/military watch. A similar look can be acheived today by shot or sand blasting a watch case, although this won't have any effect to corrosion resistance the look still has appeal.
This model has a Bulova 10BH movement ( other similar models may have a 10AK ), this comes in either a straight forward 17 jewel variant , or the 21 jewel with added cap jewels. Whilst the added jewels may have no effect on accuracy or running they do keep the pivots reasonably free from debris and prevent lubricant evaporating.
Onward to Strip down - Balance Re Fit >>
Movement Service & Balance Replacement
With the movement uncased the mainspring can be wound down and the balance and pallets can be safely removed. Close ups of the balance show the old hairspring is way beyond repair, the staff is also broken >>
With the balance removed it was also clear that the pallet stones were no longer set correctly and all trace of shellac was completely gone, with the stones loose it was no wonder the timing was erratic.
With the movement cleaned it was time to lubricate the balance cap jewel and make sure the watch was in beat >>
With the movement clean ,lubricated, adjusted and assembled it can now be recased. The movement ring was very stiff when removing so this was cleaned and a light abrasive used to smooth the walls so fitting would be easier. The casing was untouched but a new glass was bonded in place to help keep the watch sealed against moisture.
With the watch complete it was time to send it on back to the owner, hopefully it will provide more years of faithful service :)