Watchmaking is all about precision - and taking accurate measurements during the design and manufacturing process is essential. However, when it comes to the art of horology, often the relationship between arbours, bearings and gear meshing is a matter of 'how if feels' rather then how it should be engineered. As strange as it may seem, often the 'ideal' fit is not the most desired one; theoretical shapes and tolerances are not the most perfect. Why? Because tight tolerances do not necessary translate into long-term reliability or the best timekeeping under stress, changes in temperature and gravity. There is a saying that engineers are poor watchmakers which is equally true the other way around.
Some of you may remember the acquisition of a microscope for our workshop. I certainly do - we sacrificed a really fine watch in order to acquire this lovely instrument. But it was worth it! When it comes to the inspection of surfaces, part geometry, and the inspection of cutting tools, a microscope is worth its weight in gold. Trying to make a watch without being able to understand how the Swiss have done it would be impossible. So we observe, learn and try to replicate.
Here are just two examples. The first photo shows the mesh in a high grade Swiss watch. The second one is our attempt to copy the Swiss. A person with a keen eye could clearly see the difference in the meshing depth between the two examples. Without any doubt, our mesh is far tighter, more precise, and follows the 'ideal' calculated point of contact. However, we soon discovered that the sloppier Swiss way was actually more desirable. The winding action was actually smoother than ours! Lesson learned.
The second example: a short video showing the very tip of the balance staff inside the shock absorbing jewel. This is an actual recording of a high grade Swiss watch still in brand new condition. I have no doubt that any engineer (or car mechanic) would be horrified. But this is how it is, and this is how it's done. Check it out: Of course, do keep in mind that you are observing an arbour with 100 microns diameter under 240 x magnification.