M8 to Nema-17 Z-Coupler
by jameswood, published
EDIT: You probably don't want to use this. It's too rigid. I'm currently using these: http://www.thingiverse.com/thing:22422 (I think mine's prettier but that doesn't count for much if the prints suck!)
If you need a rigid coupler these are great, but for most reprap applications (including the Printrbot Plus), give mine a miss. Sorry!
A simple coupler to mount M8 threaded rods to a NEMA 17 stepper. The up arrow points up!
I'm [no longer] using two of these on my Printrbot Plus and so far, [have changed my mind about them being] so good. (Don't overtighten!)