Silhouette Cameo pen adapter

I have a very nice set of about 30 different brightly colored gel pens that I would like to use with Silhouette.The inner diameter of the adapter closely matches the diameter of those pens. You will have to adjust that based on what you have. You will also need M5 bolt with M5 nut nut to act as a set screw, or adjust the nut well size to match different screw/nut.

The dimensions in the files may be wrong -- I had to fudge them so my printer produces desired output.
(Edit: combined knob and adapter in one file, exposed customiztion parameters for OpenJsCad)