This is a set of 4 caps for the tops of the 8mm threaded rods which control the Z-axis for the makerbot. I have been lugging my makerbot around in my car almost every day, and got a few scratches on the glove compartment from the rough metal rod ends. I drafted these caps in OpenSCAD, mostly to learn how to use the CSG modeling. It's a very simple part, but it's saved me any more auto interior damage.

Each cap is a cylinder with a cone segment subtracted from it. On my 'bot they screw on fairly tight and can be used to twist the z-axis up and down. The parts are parametric, but you probably don't need it unless you want to use it to make end caps for a different size threaded rod.

Open endcaps.scad in OpenSCAD
Design -> Compile and Render
Design -> Export to STL
Skeinforge
Print
Cut away the ooze and raft.

If you want nicer looking endcaps, print the caps one at a time by commenting out the last 4 lines of endcaps.scad, and replace with "endcap();", then follow the above. Printing one at a time eliminates some of the irregularity and oozing.