Anti backlash nut for 2040 and 2020 V-slot (for 8mm ACME Lead Screw)

This is a modified version of the [Openbuilds anti-backlash](http://openbuildspartstore.com/anti-backlash-nut-block-for-8mm-metric-acme-lead-screw/) nut for the 8mm ACME lead screw that mounts on to a 2040 V-slot extrusion. A version for the 2020 extrusion is also included.

This thing is rigid and with the screw in it, its very straight and true. This makes it easy to align the lead screw with couplers and motors making it perfect for assemblies such as the Z-axis of Cartesian style 3D printe