[ChalkyChalkson]

Hi!

I'm currently working on the first steps towards designing a 3 axis CNC mill and have a pretty basic question regarding linear rails: What should I screw them to?

As far as I understand linear rails they are best used fully supported and that supported materials should be what gives the system the "flatness" constraints. So I need some kind of pretty flat materials that has good dimensional consistency between different parts to mount my rails to. I sadly don't have the tools to machine a material flat, so I'll probably be stuck with some kind of aluminium extrusion.
What should I use? Simple square tubing or one of these extrusions with T-channels on all sides? Or should I bolt raw plate to the frame and attach the rails to that?

I'm basically asking: an what type of aluminium should I expect the best tolerances out of the box?

[peteeng]

Hi CC - A CNC mill requires very good foundations for the rails. Before I answer your Q what do you intend to do with the mill? and what accuracy are you aiming at? 0.1mm 0.01mm? 0.001mm Peter