I have been working on this project for a long time. Several years ago I build a cnc router using 1" aluminum extrusion, the plastic bearings that slide over aluminum extrusion and a palm router. It was okay and I learned a lot. The biggest problem was that the frame was not very rigid and the flex in the frame made it hard to cut anything very accurate. The cheap bearings were also a problem. But I learned a ton. The whole things was my first real cnc project and I had not done much machining. I built my own stepper motor drivers as well. I was a poor college student and had to save money anywhere I could. When I moved I salvaged what I could and scrapped the rest.