rbisping did the SCAD Mendel Extruder design, and I made it parametric as well as adding support-free points over the horizontal holes. The parameters allow you to specify the diameter of the bearing race used in the pinch mechanism, its securing bolt, and the diameter of the filament.

I have also left the hole for the bearing support slightly oversize to allow fiddling for various sizes of bearing, shaft and filament.

Do not use this design with 608 bearings, as they clash with the M4 securing bolts. It should be possible to modify the design to avoid this collision - post the derivative if you do!