Using mainly commercially available parts and a few very simple fabrications.
CNC
X3
Projects
My stoopid stuff - Another great x3 convertion
Another great x3 convertion
Home Cnc Technologies
Home Cnc technologies have some very useful ideas on converting mills.
They also have an article (plans for sale) which shows how to make a ball screw anti-backlash connector.
Hoss Machine
Hoss Machine is dedicated to building all sorts or Cnc Machines and tools. You can also purchase plans for his projects. Hoss has inspired many to have a go at building and has some great ideas and designs for you to use.
RF 45 mill convertion
This Rf 45 Mill conversion has some great detail on how to convert the X3.
I adopted the toothed belt stepper mounts in a simpler less elegant design.
I also used optical sensor design.
It also shows the importance of installing oil ways.