Size matters? Ladies Le Coultre - making a new staff

Making a new balance staff for a Ladies Le Coultre cocktail watch.


I don't like to work on ladies watches, and in fact I don't know many watchmakers who do.

So if servicing was bad enough, what happens when you have a ladies watch with a broken staff, where no replacement staff's or complete balance wheels are available?

Never one to back away from a challenge, and with only one option to get this watch fixed, I went ahead and made a new staff.

First up, we need some high carbon steel. I am fortunate in that I have a large stock of 100 year old high carbon steel rods, this metal is pure Swedish steel from the Sheffield steel industry, with no impurities, something that you can't get any more.

First up the steel is heated to a red heat, then quenched, polished and then tempered to a dark blue.

The size of the rod is 1,40 mm. The first job is to cut the balance seat and top half of the staff.

Here is a view of the balance test fitted to the seat



With a snug fit of the balance staff, next I cut away and shape the hairspring roller seat along with the top pivot, the roller seat measures 0,37 mm in diameter and the pivot is 0,07 mm diameter.

Here is the top half cut away, all the work is done with a hand graver.



With the top half finished, I go ahead and work on the bottom half, cutting away material for the roller table seat. Here is a general view of that step.



And finally I cut a "V" grove before I part off the staff.



Stepping back a foot or so, here is an overall view.



Here is a view next to a ruler for sizing.



With the staff removed, I flip it over to machine the bottom half of the roller seat and pivot. The "V" grove I cut serves to centre the staff and ensure it runs true.



Once the bottom of the staff is fabricated it's time to rivet the staff to the balance wheel, before I do here is an overall view of the staff, balance, roller table and hairspring.



Here is the staff riveted to the balance arm.





And for size comparison, here is the balance next to my pinky finger...



The pivots needed some fine trimming for end shake, once installed and the beat and rate adjusted, I was able to get good results with the timing analyser.

General dimensions of the staff:

length 2,70mm
pivots 0,07mm
roller seat 0,30mm
collet seat 0,37mm
balance arm seat 0,90mm

The customer was very pleased, the watch has sentimental value and these type of jobs are very rewarding on a personal level.

Thanks for reading.

Rob

British Horological Institute Professional Watchmaker
www.roberthoran.eu

Stuff like this is just ludicrously hard. Great job...

I look at the big macro pictures and think "that's not so hard." Then I look inside an actual watch and think "that's impossible!"

Nice work.

Thanks for the feedback.


In fact, when the customer arrived to pick up her watch I showed her the photo's along with the old staff (and my loupe for actually seeing it...). She was very impressed and amazed at how small the staff is.

master miniature machine work --- hats off!

How did you determine the dimensions of the original staff? Were there prints on it or did you just measure what you could from the old staff?

The diameters are measured directly with a micrometer accurate to 1/1000 mm.

The lengths pose a real problem in determining exact dimensions, they are difficult to measure with the micrometer, this is especially a problem on a staff this small, the only solution is to use the existing staff as a general guide while cutting the new staff and of course test fitting the staff as the work progresses.

No matter how accurate you measure each surface, you still have to test fit each component as you cut the staff, I only show the balance being test fitted, but I do the same with the roller table and the collet, then of course comes the multiple fittings for the assembly into the movement and making sure everything lines up, pallet fork with roller, hairspring clearance, etc... on something this small you can imagine that the tolerances are very critical.

Very nice work!

nice craft.. !!

Phenomenal. Beautiful.

Thanks for the guided tour!

JohnCote

the ability to do that is insane.

Gosh. I find just replacing the staff on a pocket watch movement to be a challenge, but you made yours! And on a ladies watch! Incredible. Thank you for sharing this.