I think it, i tinker it, i make it!
The holders are designed for work on the FABtotum personal fabricator but they can be useful with all desktop CNC milling machines. Suitable for M3 and M4 screws, 4 mm hole on the holder.
I use this holders with two PCBs with 1.6 mm of shim, one used as sacrifical layer.
I printed the object exactly as it appears in the STL file, with the side sticking on the heated bed, i have printed with 5 mm brim.
The FreeCAD design source and a sample GCODE (4x holders single printing) are available for download on GitHub
PCB_holder_for_milling.stl → STL
PCB_holder_for_milling.fcstd → FreeCAD source
4x_PCB_holder_for_milling_PLA_210-60_infill_15_brim_5mm.gcode → Sample GCODE for print the object with FABtotum personal fabricator, sliced with Slic3r
Thing on Thingiverse: http://www.thingiverse.com/thing:1070624