I made (in Blender) these bolts as gadgets to be shared during a meeting. I gave each printed bolt screwed into a real (commercial) metal nut, perfectly mating each other. More info here: http://bit.ly/XEztcr The full video of the speech (in italian) is also here: http://www.youtube.com/watch?&v=ZWLOIle8thM The part of the video that shows my Huxley printing two bolts: http://youtu.be/ZWLOIle8thM?t=36m16s Printed in Silver PLA - nice! - from Reprapworld using my ReprapPro Huxley. UPDATE (2013/08/01): Actually the printed bolts are M10x16. I forgot I reduced the dimension to speed up printing. So I uploaded also the M10x16 file. UPDATE (2013/05/05): M10 nut added. UPDATE (2013/05/05): Nut's hexagon dimensions updated (Thanks to Balthazar)