Mendel / Prism Vertical X axis

This is a vertical X axis that conforms to the [reprap vertical x axis standard](http://reprap.org/wiki/Vertical_X_Axis_Standard). It uses a particular 10mm Acme leadscrew (Discontinued: a comparable can be found [here](http://store.makerstoolworks.com/motion/two-start-lead-screw-and-nut-single/)) but an adapter is available that hold an m8 nut for standard studding-driven mendels.

I'm not certain that the PrismX or OB1 prism conforms to the standard spacing (I'm not even sure the Sell's Men