The C64 mini fake keyboard is a joke. My keyboard is going to be functional. However it's easier said than done. I've looked around, in fact I spent innumerable hours browsing for a passable switch that would work fine in a mini keyboard. I don't intend to compete with a real modern pc keyboard, but it should be usable for entering a small BASIC program, or doing some assembly hacking. At some point I decide to just call it quits and stopped on STPMAME010 switch by ALPS.

ALPS claim 160gf in their softest variant. 160gf is perhaps soft for a vandal-proof elevator button, but it's at least 3x stiffer than your typical keyboard switch. However this is the softest I could find. Upon arrival I measured the tripping force using IKEA scales. As it turns out, they trip at full 250g, but push back 160g. They have nice long travel though, and they're still softer than a typical black 6x6 button.

Another problem is that they don't have any stem. When pressed, the stump sinks in the case entirely. So the keycap should somehow sit on top of it, but have some frame that would not let it fall off. It turned out to be rather difficult to design a keycap that would sit freely, not fall off, and not bind when pressed, all at the same time. After some 50 attempts I think I have dialed in the dimensions.

The general shape:

And then there's a frame that sits on top of this and holds them all together. Small test prints show that this works and feels nice. We'll have to see how it works with the complete keyboard though.

It's worth mentioning another discarded idea, the photo of which was used for colour tests. In case I wouldn't be able to find a nice switch, the alternative variant was to have the keys permanently attached to the frame from the top side, using little compliant hinges. They would press on tiny flat buttons. The model proved that this would work and probably it will come in handy in another project. But compliance in a 3d print is not a very reliable thing, besides it would feel perhaps a bit calculator-like.  I decided in favour of long travel switches.