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Patek Repair - Part 2, Making New Staff And Stem

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Patek pocket watch repair – Part 2, making and replacing the balance staff, new stem fabrication


In Part 1 of this repair I had to make a new arbor for the escape wheel (see my earlier post if you haven't read it).


Unfortunately the bottom balance staff pivot was bent and when I tried to straighten it out with my Seitz pivot straightner it snapped. Obviously it was much harder than normal as the pivot straightner should have been able to do it's job.

So with no access to any spare staff, I had to make one.


Here is the old staff being pressed out of the balance after I cut away the rivet. Someone had previously replaced the staff as there was a slight bit of material removed around the balance arm hole.




With the staff removed I was able to take the dimensions and make a new one from round silver steel stock. Luckily the staff is quite large and measures just over 5.00mm long making it easy to work with. The pivots measure 0.10mm.




The new staff was riveted to the balance and the roller table installed before it was poised. Poising is checking and adjusting the balance wheel to make sure that it doesn't have any heavy spot. In other words “balancing” the balance wheel so that all the mass is centered on the pivots. Poising is mandatory and always required after a new staff is installed. If the poise is off and the balance is heavier on one side the vertical rate will not be accurate.







The original stem was in very poor condition and did not fit the hole in the mainplate, being somewhat too small which was causing all sorts of problems.







Here's the new stem I made




In this view you can see that the new stem fills completely the mainplate hole, no side play anymore



Edited by Horlogerie
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Another masterclass in watchmaking, thanks for sharing Robert and keep them coming! :)

I was having a look at your avatar, the microscope on the boom arm must help enormously when using the lathe.

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Another masterclass in watchmaking, thanks for sharing Robert and keep them coming! :)

I was having a look at your avatar, the microscope on the boom arm must help enormously when using the lathe.

Thanks for the kind words.

Yes indeed, the binocular microscope was a great addition to the shop. Using the lathe with a 4X loupe is not too difficult for normal jobs, but when it comes to staff's and small parts requiring 7X with the loupe, the working distance and depth of field is so small that it quickly becomes very tiring.

I picked up the binocular microscope and haven't regretted the cost at all. I can easily turn a pivot to 0.08mm without any difficulty, whereas with a loupe I would struggle at 0.10mm diameter. As well with the microscope I am sitting back and completely upright.

The only drawback, inspecting anything you do at 4X with a loupe under the microscope shows just how poorly 4X can be in terms of finish, oiling, etc, sure makes you quickly improve your attention to detail.

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Thanks for the information regarding the microscope. It is something I have been considering for a couple of years now, especially for lathe work. I'll struggle on to Christmas using my visor, and when the other half asks what I would like, I'll have the answer! :)

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Amazing job Robert, thank you so much for posting this enlightening work! A new goal for us latheless folks that have a lathe in the wish list pending wife approval! This is the type of work that makes what is seemingly impossible, possible and inspire the rest of us.





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