Sanding bow

Simply attache 20mm wide sand paper with one screw on each side. 

Tighten the screw to close the jaw and sand your part.

The part is best printed laying flat on the bed so you print perimeters with open jaw, that helps printed part to be strong enough while tightening the screw.

Printer settings:

Perimeters - 4 and more. For better strenght of the model.

Support - if you want nice smooth round edges.

Nozzle - I used 0.25 :-)

If there is a need I can also make version with hexagon nut. Let me know in comments :-)