New model files have been posted. They are now sized as millimeters. The previous models were posted as inches.
This mechanical finger can be a lot of fun to play with, but can possibly serve as prosthetic for someone with missing a thumb or other fingers. Additional parts needed: a basic flexible "BIC" pen insert. Four (4) M3 x 10mm screws with washers. Other small screws may be substituted.
Support is a must. I have positioned models at an angle that has worked well for me.
I recommend 3 shells for wall thickness.
Some clean up will be needed, depending on the type of support used.