This is a key cap set I worked up for my Dactyl Manu-Ball keyboard project:
https://www.thingiverse.com/thing:4306733
The shank or shaft is designed to fill the space with as much material as possible to give the cap a real solid connection to the switch.
I printed my set with ColorFac XT-CF20 which is a tricky material to print with. I also over extruded the white by 10% so ensure it filled the area between the black more completely
ToDo: Chamfor corners around face of cap.
I over extruded the white by 10% to make sure it filled in all the corners of the characters. The black is ColorFab XT-CF20 which is a tricky material to print. I only used it because I liked it matte black finish
The author hasn't provided the model origin yet.