I am in the design stage of my router/plasma table. I am building it for the router but may plan down the road to use it for plasma. This will be a 3.5(travel) feet by 8 feet table. Anyway, what is the preferance with the Z axis? Much cheaper to use ground shaft and linear bearings but I see a lot of people using THK style rail bearings for the Z axis. I want to run 2 parallel linears (round or flat) say 5-6 inches apart with a ballscrew down the middle. I was thinking 3/4 inch shaft with bearings? Should I consider rail style bearings instead? What would the advantage be? Less flex? I am going for about 8" of travel so my shafts or rails will need to be around 14-16 inches long depending on my final design. What are some thoughts?