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First time for me placing my hands on a true watchmaker's lathe to repivot a central wheel (small seconds), under the guidance of my mentor master Lino. 

Work isn't complete and  practically it never will be, because ase the pinion was picked from a box of spares that he accurately set aside.

Lots of of technique details were passed to me, probably these are explained in most books, but the experience of learning first hand is priceless! 

 

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15 hours ago, nickelsilver said:

Why did you remove it from the wheel?

To anneal the pinion before drilling. I used an HSS bit from the vintage set below. It could have done with a carbide bit on the hardened part, but we didn't have any, and there is always the risk of breaking the bit. The hole was started  with a center drill made from a broken bit,  then I manually sharpened a long bit on a small stone. It drilled very well with short pressure on fast spinning, quick retreats and a droplet of oil.

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Now, the main disadvantage of annealing was that master wanted me to coat first with boric powder to avoid bluing the part, that required a good time to clean up the resulting scale. 

14 hours ago, oldhippy said:

Who is master Lino? 

It would take take a long posting to tell his experience and achievements, and I want  to do that as soon as possible. For now I'll just say that at 96 years young he's incredibly active and I am lucky to take precious lessons from him. 

13 hours ago, ThrobinsonCrusoe said:

Did you turn this on the lathe or repurpose it from a spare part?. I'm confused

I should explain. He saved some broken centre wheels, like snapped at the cannon pinion arbor section.

First, a sketch of the pinion and all dimension is made, that would be very important in case the part is misplaced or lost.

Then a suitable diameter steel wire is selected from an assortment like the below -that is a very vintage one, but such wires are still made today, it is cut of sufficient length. Within the same nominal size, the nearest one can be picked using a micrometer. There can be a difference of one or more cents of millimeter that will help reaching the best result with the less effort in the following steps. 

Then the pinion is drilled as above. It could have been repivoted on the broken side only, but for practice I drilled through and repovited both sides. 

The wire is fitted first within the lathe, then one can use the staking set, as the typical hole depth of a stake is perfect for the purpose.

In my case it fitted tight and strong so not to require cement, and to improve friction one can roughen up the contact area rolling the relevant section of the wire between two diamond files, exercising strong pressure and very short travel.

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I did not made further progress today as we got caught with other contingencies. 

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Final update, the outcome is not perfect.

For practice only, we took a similar cannon pinion that needed the arbor to be reduced by about 0.1mm. This is done by turning a bit with the pin in a female center on the tailstock, and pretty much any tool, on the carriage. Once is measured close, the center is removed, the end filed so the pinion can be tried and the last cents removed. In reality excess could also be cut off at this point. Reducing with a file is not easy because you have to work evenly, and identify the precise spot that prevents the pinion to fit. The file can be placed below the work, handle away from you, to observe where it leaves a so faint streak. Being my first hands on with a watchmaker lathe I evidently overfiled, then removed the blocking spot and all of the sudden the pinion became a trifle too lose. I proceeded anyway to cut the groove, which must be precisely positioned. That also did not produced a good lock, for as much I tried to tighten the cannon pinion. 

I'm happy anyway and just hope to do better the next time

 

Edited by jdm

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