Silver Pocket Watch Chronograph

Oliver sent me this lovely pocket watch for a service. It is in a silver case, and has a chronograph complication, with a centre seconds chrono hand and 30 minute register. There is also a seconds subdial at 6 o’clock.

The case and movement have a matching serial number, so it is nice to know that the movement is original to the watch.

After studying the hallmarks on the silver case, I was able to identify the marks of the London assay office used in 1913-1914, so the watch would have been produced around that time. The “sponsors mark” belongs to George Stockwell, who was an importer of cases and watches during that era. Service-Pocket-Chronograph

The Chronograph movement is a Column Wheel type, as you can see from the castellated wheel on this photo. Each click of the pusher (in this case the crown) turns the wheel by one tooth, and the columns on the wheel move the various levers to engage, stop and reset the chronograph.Pocket Watch Chronograph

 

The Chronograph coupling mechanism is a tilting pinion type.Tilting Pinion

 

 

I start by conducting an appraisal of the watch and movement. The amplitude of the movement is poor at 176deg, it is definitely time for a service.

 

 

The chronograph does function, but unfortunately it consistently stops after one minute, and this causes the whole movement to stop. It seems the chronograph wheel finger does not have quite enough energy to push the minute counter wheel one “notch” for every minute. The service will reduce friction and energy losses, and with the correct lubrication, I am hopeful this will take care of this.

 

The movement is removed from the case. The enamel dial is in beautiful condition. The hands are positioned at 12’o clock ready to be removed with a lot of care.

 

I start disassembly of the movement with the dial side.

 

I fully strip the dial side, but I temporarily stop at the ratchet wheel, which puzzled me a little bit, as I have never come across this design before.

The ratchet wheel is secured on the barrel arbour with a kind of washer. There is a recess in the wheel to allow space for the washer. My intuition is telling me that it should slide out, but I am worried that attempting this could cause irreversible damage: the washer sits very tightly in the recess with very little play, and will butt against the edge of the recess in the ratchet wheel.

I ran this past a few fellow watchmakers, but none of them had ever come across this before so I am going to have to figure it out by myself!

 

The part is more than one hundred years old, so you can imagine the chances of obtaining a replacement are nil…I decided to sleep on this.

 

I come back to it the day after for more thinking and observation. I notice that there are wear marks along the edge of the slot, which gives me the confidence to try a bit harder to slide the washer.

 

 

 

I apply pressure at the end of the slot with a piece of pegwood to avoid any scratches, and eventually the washer moves and its edge goes over the recess. Hurray!

 

 

 

What becomes obvious only after disassembly  is that the washer is actually dished, and therefore acting as a spring (hence the absence of play I had observed).

 

 

 

So it has the ability to flex to go past the edge of the recess of the  ratchet wheel, the area I was very concerned about: I was expecting a flat washer, which would have simply butted against the edge, no matter how much pressure was applied.

This was the only difficulty I encountered during the disassembly process, so I now fast forward to the point where the movement is fully stripped down and all parts have been cleaned ultrasonically.

 

 

 

I remove the endstones. As you can see the upper side is rather dirty despite the earlier ultrasonic cleaning.

 

 

 

Some will advocate just cleaning the end stones ultrasonically without removing them, and oil them through the jewel hole. It would certainly save time, but I much prefer removing the end stones to lubricate them and make sure they are immaculately clean. If you can’t inspect you just don’t know what is there, and the tiniest amount of trapped dirt will be enough to prevent the optimum performance of the watch.

The jewel is manually cleaned, lubricated and fitted to the balance assembly.

 

I do the same on the dial side with the other end stone.

 

 

I then rebuild the barrel and mainspring assembly.

 

 

 

 

 

 

I re-assemble the train.

 

 

 

 

And eventually I have rebuilt the whole movement. At this stage, the movement is running very well, with an excellent amplitude between 275-300deg.Tilting-Pinion-Chronograph

 

Unfortunately the chrono minute counter is still struggling to go in one minute increments, I can see it is trying, but failing, hence still stopping the watch after one minute when chrono function on.

Despite the increased power delivered after the service, and the reduction of energy loss with cleaning and lubrication, it is still not working. After more investigation and troubleshooting, I manage to trace the cause of the issue. The hammer is very lightly rubbing against the minute counting wheel, and causing enough friction and loss of energy to stop it from moving a full increment. This is caused by the hammer post which has worked itself slightly loose and is tilted at a very small angle.

So I tighten the post, and the chronograph minute register now works perfectly.

 

With everything working the dial and hands are ready to go back on the movement.

 

And before re-casing the movement I polish the silver case. Silver does tarnish quite quickly, and the case was a dark grey/ black colour when it came in. After a polish and ultrasonic clean the case is looking fantastic again.Pocket-Chronograph

 

I would like to sincerely thank Oliver for giving me the opportunity to work on this very interesting watch. This project has been a real joy to work on. I always enjoy the diversity of the watches arriving on my bench, and these old watches always feel that little bit more special to work on.

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