Updated version with knob spinner on to: http://www.thingiverse.com/thing:847254 It's often useful to be able to create threads in plastic holes so that things, like circuit boards, can be secured in place with tiny screws. I have a set of taps for just this purpose, but the heavy steel handle I have didn't really work well -- because it is hard to feel what is going on and I've stripped plenty of holes. This tap handle tapers so you can get more torque if held near the butt end, or more speed if held near the connecting end. It works quite well. You may need to adjust it for your taps though -- my taps have a square attachment end that is about 2.8 mm square. I found that with my printer (LulzBot Mini), the plastic oozes to the sides as it is printing, and that a 3.5 mm hole for the tap takes this into account perfectly. YMMV. There are four holes for a 2-56 threaded screw at the end to secure it. I only use one screw -- I figure the extra holes are there to be used when I eventually strip a screw hole. Made with FreeCAD -- source file included.