Creating overlays / custom key kaps for cherry switches

[sa-penguin]

If you're looking at keycaps for a calculator...

Will you be using functions, and / or multi-functions? On a standard keycap, the shifted "!" is usually above the " 1 ". If you have more than one function, or you want to use a word, or even an equation like "log x" you may need to use the FRONT of the keycap - and maybe a different color.

Using the front of a keycap means you probably want "DSA" or "G200" format, which tend to have a low profile and a slanted front - increasing visibility of any front text.

If you're designing a one-off set, I'd suggest decals. I'd also suggest white / light gray keycaps, to increase contrast when your CMYK printer ink makes labels on transparent paper. If you insist on white text, home-made decals are going to be a problem. Not impossible, just... tricky.