I am considering trying to replace a broken staff, I have replaced a few staffs in pocket watches, but never in a wrist watch. Are Bulova staffs riveted or friction fitted? Any pitfalls I should watch out for? Anyone have any tips or advice, would be appreciated.
Gary
Same as on a pocket watch, only much smaller, obviously. They are riveted, and the biggest pitfall is removing the old staff.
Do NOT use the punch method, even if you have the special staff removing punches. It is too easy to distort the balance. There is an excellent tool for this, but unfortunately no longer available, although I am still trying to find one that I can get some pics of. However, we were taught to turn the rivetted portion off carefully on the lathe, and this yields good results. Just be careful riveting the new staff, too much force can injure the balance or the staff, or both. You still have to poise the balance, and this must be painstakingly done. I find that even if you use the correct replacement staff, oftentimes the collet may be loose when you go to reinstall it, and sometimes the staff must be fitted further, ie. pivot shortened slightly, etc. Obviously you cannot make the staff longer, and if you find the endshake unacceptable, you must start again with another staff. I don't know why exactly this is, it may have something to do with quality control, or certain batches, or whatever. It's irritating. One shouldn't have to test the staff first in the balance to see if it even fits properly, but it can save a lot of time. I always assumed interchangeable meant interchangeable, and standardization meant just pop the thing in, and it's perfect, but this is not always so.
Also keep in mind that the staff that is in the watch may also be incorrect, unless you KNOW it was running well before it broke. History is very helpful, and not always available in this age of eBay. I did a vintage IWC and the staff was a close match, but not exactly right, so the one I made based on it was also a bit off. ( I know this because I found the correct staff after) I invented some new swear words for the occasion.
The whole process is time consuming and must be done correctly. The balance is the most critical part of the watch, and there are no shortcuts apart from getting a new balance complete in original packaging.
Anyway, hope this helps.
Thanks Reverend Rob for the quick reply and your advice. It seems I may be stuck before I start, as I don't have a lathe, I've always used the staking tools, plus I haven't operated a metal lathe since shop class in high school about 40 years ago. On a side note, I have a small staking set, about 1/3 the size of the usual sets, there is a staff removal attachment that is not the K&D type, appears to use the same principle for use. If you'd like I will send a pic.
Gary
I have used the staking tools with their staff removing punches, etc., and have found that depending on the staff and its rivet, miniscule distortions occur which play havoc when replacing the staff. When I was apprenticing, a Master Watchmaker told me of a tool he used that never harmed the balance wheel. He described it, but I have never seen one. If he can locate his, (he hadn't done any staff work for many years) I will get some pics of it. My understanding is it doesn't drive the staff out, but cuts the rivet.
In the meantime, I am all for keeping parts pristine, and if there is even a slight chance of damage, I will go the slow route, especially when it comes to balances. If you can lay your hands on a good used Boley (or Levin, or some of the English ones) watchmaker's lathe for a couple hundred bucks, they are well worth the investment, as I use mine for everything. Usually you will find the lathes offered for sale with few accessories, and you then have to hunt down all the missing collets and attachments, but this is well worth the effort.