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 files already have a bit of slop added because I was having trouble with it threading easily. It is not recommended you scale one component down/up to change the tolerance between threads as doing so will scale the cone shape that the collet is sandwiched by, which reduces the holding range. But if you don't care about holding smaller diameter pens, go for it.

The mounting holes are sized to fit an M4 screw and washer

short video of it in action: https://www.youtube.com/watch?v=DikeSm8y0DI