Thursday, September 6, 2018

What is a micron and why does it stink?

A micron is a unit of measurement so small that engineers are constantly struggling to find an appropriate analogy to describe it to students. I’ll provide you with two analogies today which hopefully will demystify this subject forever. The first is my own, the second one comes from a German school of engineering. 
Imagine your watch grows to the size of an oval which is 40 metres in diameter. And this is just the dial size - the winding crown is 6 metres further away. If you are standing in the centre of that oval, you will be standing right on the top of the minute hand and on top of the centre wheel. I am standing 15 metres further from you . (We are the two pink straw men in the drawing.) In the watch, this is the distance from the centre wheel to the balance wheel. Now, if you yell ‘move, come 1 millimetre closer to me’ that would be a crazy small step, but if I were ever able to move just one millimetre closer, that step would be the equivalent of two watch gears moving closer to each other by 1 micron.    
The Germans are more pragmatic: imagine you are standing in a Bavarian cow paddock. You see something in the grass and you pick it up. It is cow poo. You wash your hands 3 times with soap, then once again.  That stink that you can still smell is one micron. 
I am not making this up. This is precisely what Josh and Tyler were told at the Kern factory on the first day of training.
Whatever analogy you prefer – one micron is something incredibly small, yet incredibly important, because when two watch wheels are just a few microns too close or too far apart, that means the difference between a working and non-working timepiece. 
There is a great video about Vaucher manufacturing. Actually, this is one of the most important videos you can find on watchmaking. A watchmaker in the video says: “It is so easy for an engineer to pick a pen and write on a drawing ‘plus 1 micron’. For a watchmaker, to actually machine such a part is impossible.”. 
And this is precisely what our quest is all about: not to make anything within a micron but to find out how close we can get to it – or how far away from it we can get away with – while the watch is still performing as close to perfect as it can.  

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