About this 3D model

I was having trouble getting the smaller gears to print because of the overhang. I used OpenSCAD to fill in the bottom of the hole on each gear so that there was a clean bridge. I left enough of the hole to act as a guide for the drill. The scad files are created demonstrating how to do this. The import feature in OpenSCAD provides a convenient way to make simple additions and deletions to an existing part if the only thing you have is the STL file.