Stopwatch repair--new staff...lucky find.

[LittleWatchShop]

This stopwatch has been on my radar for six months.  It had a broken staff.  The thing is not worth much (if anything) so I did not want to buy a donor and I was having no luck finding a staff on ebay.  Then a couple of days ago, I was rummaging through a parts drawer and saw a Vigor assortment of "pocket staffs."  What the hell, I poked around in the box and found a staff that was VERY close.  This staff uses a brass finger rather than a roller jewel.  The diameter of the post of this new-found staff was much too big, so I decided to turn it on my WW lathe.  Boy, oh boy, I was very careful and very slow.  Thankfully my new gravers arrived so I had beautifully sharp tools to do this work.  After lots of turning, I got it within 10 microns of the necessary diameter. 

Before installing the finger, I needed to put the staff on the balance.  Uh oh.  The diameter of the balance hole was greater than the diameter of the staff.  Not by much.  I have watched some WRT videos where the staking set is put to good use.  I learned from those why there are curved faces on punches!!  So, I put the balance on the staking tool, and gently (sometimes not so gently) and carefully, punched the balance to close the hole a little bit.  Ahhhh...success!!

With the staff installed, I set the finger on.  Then the hairspring.  LOL...positioned the hairspring way off!!  I should have studied the balance cock first.  Oh well.  But I got it on oriented properly.

After installing the balance...no tic toc.  Hmmm.  Well, the problem was the pallet fork was not engaging the finger on the staff.  The fork was too high.  OK...here is where I broke a fundamental law of horology...dunno...you be the judge.  I was so close, I decided to bend the arm of the pallet fork just slightly downward.  It was enough.

Tic toc.

I may not yet be done.  I am letting it run to see if there are any glitches.

My satisfaction is derived in large part from actually using the lathe to accomplish a real task!  My dad is smiling from heaven.

Thanks to @nickelsilverfor guidance on the A-B magnitude question.

[LittleWatchShop]

Been running all afternoon!!

[Tmuir]

Congratulations in getting the stopwatch running again, fitting a balance staff is not easy.

It looks like you got away with it this time, but generally closing the hole on a balance wheel to fit the staff is not good practice as you can't control how the hole closes in and this can end up with the balance staff being off center and put your wheel out of balance.

I guessing we won't be timing the Olympics with this stop watch so it probably won't matter but I wouldn't recommend doing this on a watch you plan to use to keep good time.

[LittleWatchShop]

35 minutes ago, Tmuir said:

It looks like you got away with it this time, but generally closing the hole on a balance wheel to fit the staff is not good practice as you can't control how the hole closes in and this can end up with the balance staff being off center and put your wheel out of balance.

Great point.  I knew I was wandering from the true course of rectitude!  This is only my second staff replacement--the first one was done by the book.

Thanks for the insight.

[Tmuir]

Wait to you have your first go at making a balance staff from scratch and you have spent 6 hours on it  and as you take the final pass for the roller jewel to give a good friction fit your son comes into the room to ask you a question and distracts you and you accidentally take off 0.02mm too much and the friction fit for the roller jewel changes to a sliding fit.

Then you part off, put it in your collection of failed staffs and start again..............

[LittleWatchShop]

34 minutes ago, Tmuir said:

Wait to you have your first go at making a balance staff

Actually I tried to make this one from scratch.  The hardest part was that longitudinal kerf.  I did get a kerf cut and then when I was close, I busted the pivot. Argh...had to just walk away.

I have great respect for you guys who can do this!