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Only fools will go…
Don Corson, 18.10.2005

I am taking my first foolish steps in watch making and thought others might like to see the results of my work and how I got there. Maybe it will inspire others to try their hand at making their own watch too. I am just at the beginning. I do not know as I write this if this watch will ever really work. But even if it doesn't, there is the adventure of learning, then the next will be a success.

My interest is in making watches. Any interest I have in learning repairs is motivated by my desire to get the necessary skills for making my own watches. I would like to stress the fact that I am not a professional watchmaker and have not yet finished the first year of the BHI correspondence course up 'til now. There are certainly much better ways of doing things than mine. If so, please let me know. I am grateful for any aid.

This first project is to take the wheels from a standard calibre, an ETA2824-2, and make the rest of the watch myself to create a watch like in the images below, in declinations for a mans and a woman’s watch:

The project started out with much time studying the 2824, measuring and CAD modeling of all the parts I was planning on using. You will note that I have moved the seconds from the center as in the ETA2824 layout to a more northerly position. This causes me to completely change the wheel placement in the movement and use some 2824 parts more than once to span the distances, but the plan is not to cut any gears myself for this first project.

The plate and bridges look like this in the CAD:

This is a rendering of the going train, motion train, keyless works and bridges, without the plate.

Between the plate, barrel bridge, wheel bridge, anchor bridge, balance bridge and motion works cover there are only 104 different holes to be drilled in 10 different diameters. To assure some chance of the thing working I am striving for a positional accuracy of 0.01mm for all holes.

Below, you can see the first steps. From the left, the plate in 2.5mm brass, bridge plate and anchor bridge in 1.5mm brass and the motion works cover in 0.3mm brass.

This drilling was followed by turning all the recesses to depth on the lathe, the non-circular recesses thereafter on a milling machine. The plan is that the recesses are turned to the level of the inside face of the jewels when there is no play on the shaft. Adding the endshake will put each jewel about 0.05mm below the surface. It will be seen how this assumption holds up in reality later, but it should give me some small amount of leeway for correction in both directions if necessary.

The outside dimension of the movement is cut out with slots. The excess material left attached to be able to better hold the pieces for if (when) any further machining is necessary.

You will also notice the markings for cutting this "bridge" plate to form the barrel bridge, wheel bridge and balance bridge. In the picture below, the barrel bridge is almost separate from the rest.

With the bridges separate it is now necessary to be able to position them accurately. To this end there are two positioning steady pins mounted on the plate for each bridge.

A first check shows the countersinks for the screw heads are OK, but some of the steady pins are still too long. I made countersink tools for the heads of the two screw sizes I am using. These are the screws from my previous post on this forum. The tools were made by grinding down the shanks of broken tungsten steel drills to the correct form. When chucked up in the lathe they cut very well. I don't think that for this use, for cutting brass, there is any advantage to that compared to turning them with a graver in silver steel and then hardening, though. I found it very difficult to get anything like a sharp corner while grinding.

In these pictures you can see one of the effects of using only pre-existing wheels. The placements for the train from the crown wheel to the ratchet wheel show prominently here. Two extra crown wheels are used to span the space between the original crown wheel and the ratchet wheel, while maintaining the proper sense of rotation. This space is because I placed the barrel to the other side of the movement compared to a 2824.

Things will get more interesting in the next installment as I place the jewels and hope that the precision of my measuring and drilling was such that the wheels all fit and turn freely.

Still a long, long way to go…

Don

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Copyright © 2005 Donald W. Corson