Collet Type Pen Holder for CNC Plotter

This is a collet type holding mechanism for pens of 8 to 10 mm diameters that I designed to use on a CNC Plotter. The collet is symmetric across the x axis to reduce uneven stress that would cause the thin cross sections from delaminating when clamping smaller diameter pens. I'd recommend printing the actual collet out of PETG or something with a little more flex than PLA and the "holding" components in PLA or something that can maintain the threading under load.

The threading in the STL fil