First Balance Staff Replacment

June 2009.

Still being a beginner at this game I thought I'd share my recent success (or at least partial success, more on that later).

Here is the subject:

A 7 jewel Waltham model 1894, one of three purchased on EBay. I choose this model quite on purpose as most of them have a friction set balance rather than a riveted one, meaning one less difficult task to deal with.

Here is the old balance disassembled:

I do not have the special stakes sold by K&D for the Waltham friction staffs, however I had little difficulty in removing the old staff with stakes from my standard set.

As you can probably see, both pivots of the staff are gone and both pierced jewels are cracked and broken out. Don't know what happened to this poor watch but it wasn't nice. Now comes the fun part: Scouring the internet to find new parts. In the end I went to DashTo.

New Parts:

 

Since I was replacing both pierced jewels I got them matched in size (there are 3 pivot sizes used in these watches). Since I knew there was going to be some practice involved in this task, the staff is one of a package of a dozen generic (over-sized) staffs rather than a factory part.

Now comes the interesting part. First I carefully measured the critical diameters of the old staff:

 

Every diameter of the new staff was about 0.01-0.03mm too large. To make the necessary adjustments I choose to use a small Arkansas stone slip and my lathe:

 

 

Now at this point I should mention that in this process I destroyed four of those replacement staffs. Two were "resized" to the point where the roller would simply fall off. Two new pivots were snapped clean off. But then that's why I bought a dozen

The pivots were resized using the same slip. Testing them after every tiny bit of grinding in the new jewels until they fit in and tip to the proper angle.

Finally I got a new staff that I was willing to believe was correct, and used my staking tool to press it into the staff:

 

And now comes the moment of truth. Mounting the partially assembled balance in the movement. It spins nicely until the balance cock screw is tightened.... The new staff is a hair too long (not really surprising). So back to the lathe, and a few gentle touches with that same slip striving to make it a hair shorter but not create a flat end. And sure enough now when installed in the movement a small puff from my blower sends it spinning like at top!

 

Back to the staking set, to press the roller back on. Note that it free falls halfway down the taper like is supposed to:

 

There is still a lot to do. I put the assembled balance on my poising tool and it seems to be in pretty good poise with no adjustments (is this typical?) I have not yet attempted to burnish the pivots I figured I would try and get it to run before that step. And of course that leads to the next learning experience: Here is the state of the pallet fork:

 

Over a year later I get around to working on the pallet fork.