From The Verge:
The secret: there are actually three buttons connecting each Apple Watch strap, two of which interlock so precisely that Apple had to rethink its entire approach to manufacturing. “The tolerances in there are kind of insane,” say our sources. “It’s super hard to machine. You can’t get tools in there; the angles are all weird.” So the company wound up buying Swiss CNC machines that cost up to $2 million — each — just for the sake of its swappable band system. “It didn’t cut anything else on the watch, just this, that’s all it did.”
Just lots of really neat engineering in here. Fancy CNC machines that Apple bought more of than any watch manufacturer ever. A button that relies on tolerances close to 5 microns (an average human hair is 70 microns thick). Awesome engineering, and cool blown-out 3D diagrams.
If Apple would only make movies/documentaries/TV series about this stuff, I would pay double my subscription fee to watch them all on Apple TV+.