Jewelling a titanium mainplate - NH55 update

 

Today is a very exciting day!  We are assembling the first mainplate from our batch of NH55 watches. The NH55 is incredibly unique in many ways - Timascus dial, with guilloche, individually laser welded titanium indices on the dial, feathered numerals and batons, feathered hands, blind sub-seconds hand, the list goes on and on... But one of my favourite technical differences for the NH55 is the Grade 5, Titanium mainplate.  The mainplate is the most complex component in the watch, with over 80 critical dimensions many of which are toleranced as tightly as +- 2um. Many of the tolerances in the mainplate are associated with the holes in the mainplate. Holes for pins, holes for jewels, holes for clearance, holes for threads.

Making mainplates in brass is "relatively" easy - one reason why brass is an easy material is that it is soft. All the press fits, for jewels and pins, benefit from this. A soft material allows for larger tolerances to be accepted for these press fits. For example, a 1mm pin would press nicely into a 0.98mm hole, a 0.99mm hole, and even into a 0.995mm hole!

Moving to titanium, this all tightens up. In fact, press fitting parts into titanium is incredibly demanding! That same 1mm pin will not fit into a 0.98mm hole. A 0.99mm hole would fit, but would require too much force to press in, and a 1.00mm hole is too loose! So, the tolerance for the hole diameter in titanium for a 1.00 press fit is between 0.993 and 0.997, just a total tolerance of 5 microns! For context, a human hair is about 50-70 microns in diameter. So, the difference between a functional mainplate, and an expensive paperweight is just a tenth of a human hair! To further complicate things, there are no less than 80 dimensions in the watch that have this sort of tolerancing!

Manufacturing parts like this is a huge challenge. It takes weeks of process development, trial and error, and feedback loops to get to a point where everything just... fits...

So, today is a special day - Andrew is press-fitting the jewels and pins into our first Titanium, NH55 mainplate!