Tuesday, 8 May 2012

Watch Revival (Number 1)

Hello and welcome to the first of our new series of posts about mechanical watch revival. Within this series, we plan to take you through the basics of bringing mechanical wristwatches back into service. We currently only make battery-powered quartz watches, but are very interested in the history of mechanical watches (which are powered by winding up the mainspring). Join us as we learn about the process of servicing these timepieces, perhaps picking up new skills as we go.

Crispin Jones (AKA Mr Jones) has been attending evening classes in watchmaking at Epping Forest Horological Club for about six months now (watchmaking is essentially watch servicing and repairing). We are planning to produce some mechanical watches in the future, so this course provides a good grounding in the principals. In this first post, Crispin works on a French "Trench Watch", firstly describing a little of the history behind it.

Trench Watches are amongst the very earliest wristwatches that were produced for men. The practicality of wearing a watch on ones wrist first caught on amongst the military during the Boer war (1899 - 1902). This military adoption of the wristwatch became more widespread during the first world war, hence the term Trench watch as a catch-all for these early wristwatches. Wristwatches for ladies existed earlier - there was a fashion for them from about the 1890s, but this seems to have been a passing fad.

The Trench Watch movement is a basic mechanical watch, the wearer needs to wind it up every day. The winding tightens the coils of the mainspring that provide the motive power - basically this spring is allowed to slowly unwind and this energy is used to move the hands. 

Mechanical watches should be serviced every three - five years, servicing involves disassembling the watch, cleaning all the parts, reassembling and applying a little oil to the the moving parts (the watch movement was designed to be serviced in this way). This probably seemed like a scam dreamt up by watchmakers to earn money, but as the parts of the watch are constantly in motion for all the time between services it doesn't seem so unreasonable. Of course human nature means that most people wore their watch until it stopped working, at which point they took it in for repair (or brought a new, more fashionable one). I suspect that this is what happened to this watch.

About this watch:

This watch came from ebay in France, although it is not hallmarked (as would be a silver watch sold in England from this period), so we cannot date it exactly, however I am confident it derives from the first world war. It bears signs of being for military use: it has an (overprinted) 24 hour dial and you can see the remnants of the radium lume that allowed the time to be read in the dark. The style of the movement and the porcelain dial further serve to place it to within the first 30 years of the 20th century.

I was drawn to this particular watch as an archetype of the early, military watch. The size of the watch is slightly smaller than would generally be considered a man's watch these days at 32mm, but it sits nicely on the wrist.  

What I did (with some help) to repair the watch:

I should say at the start that I'm not trying to provide technical instruction here - it's more a record of what we did to get the watch back to life and I have omitted some stages. The watch was not working when I received it, and indeed it had lost the winding stem and crown. I purchased a mixed lot of winding stems (from here) and managed to find one that fitted (it was the second one that I tried, so I got very lucky!).

I disassembled the watch completely (this part is generally quite straightforward). You can see (almost) all the parts laid out in the photo above, this sequence represents the third time I'd reassembled the watch and for expediency I left the mainspring inside the mainspring barrel (middle row, extreme left) and also the balance spring attached to the balance cock (top row, the lower piece to the left of the dial). 

I cleaned it in a rotary cleaning machine: you load the parts into a little metal basket and then spin them for several minutes in the cleaning solutions (I'll get some shots of this for the next watch, so you'll have to imagine this for now if you've never seen one). The parts are then spun dry in a little heater. After this the jewel holes are "pegged out" this basically means you twiddle a little stick inside them to remove any dried on oil residue that the cleaning machine didn't shift.

After cleaning I reassembled and oiled the watch. The watch has a tiny amount of oil applied to the jewel holes where the pivots of the wheels rotate (the jewels are synthetic rubies, so not of any value!). The oil is applied when the watch is assembled - a single, very small drop of oil is applied with a flat piece of metal called an oiler. You aim the drop of oil at the gap between the wheel pivot and the edge of the jewel and capillary action draws the oil into place. The oil then forms a thin layer that allows the pivot to rotate freely within the hole. The pivots are specially shaped to prevent the oil simply running away and dispersing through the watch.

The first time I assembled the watch, it all worked fine however there was a problem with the mainspring inside the barrel: when you wound the watch up the mainspring would not catch at the end of it's winding (basically it was loose inside of the barrel). This meant that the watch couldn't be fully wound. My tutor Richard helped me put a new bend in the end of the winding spring, you can see this in the photo. This hook allows the spring to catch onto a little protrusion inside the mainspring barrel, the second photo shows the spring wound into the barrel, Richard has an oiler in his right hand and (I guess) has just applied some grease to the coils of the mainspring before closing the barrel. 

Once assembled and oiled I hooked the watch up to a timing machine that acoustically processes the "tick-tock" noise to judge how well the watch is keeping time. By adjusting the regulator needle on the balance I managed to get this watch to the the point where it was +-12 seconds per day which is considered excellent performance for a watch of this age and quality of manufacture (this was not an especially expensive watch when new).  

I've worn the watch out and about several times, it runs very well and should be good for plenty more years of service. 

Date: around WWI (1914 - 18)
Movement size: 12 ligne (27.07mm)
Watch size: 33mm diameter
Jewels: 15
Made in: possibly France or Switzerland
Features: stem wind and set / sub seconds at 6 o'clock / 24 hour markings on dial

The movement is nicely finished under the dial (this type of finish is called perlage). This is a side of the movement that would never ben seen by the customer, so shows that there was some pride in the overall quality the movement.

On the dial side there is a Swiss patent number 51482, which relates to the crown mechanism without setting lever spring. Patent filed 05-03-1910 by Fontainemelon Horlogerie, CH (FHF)

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