This is the V1 push fit pin and socket that I have made.

I have used this in models by download the .stl file then scaling to whatever size you would like. I added a cylindrical hole the size of the socket into the socket side, inserted the socket in the 3D software of choice, then added the pin to the opposite side.

The smallest I have tested is (lxwxh) pin 1.5x1.5x1.5mm with the socket being 1.5x1.5x1.61mm - the photos show this on the test connection with the other photo showing a 6mm pin & socket.

These have all been printed on a 0.4mm nozzle.