Hello All,

i am in the process of building a Cnc Mill. I have a rough table built in Sketchup and am in the process of buying the material for the table. i am using 4"x8".25" tubing A500 B steel for the table build. I would like a working area of about 5'x10' I know this is rather large but the table will have its purpose with these dimensions.

I am also looking into some railing for the axese and this is where I have little knowledge and experience. I am looking into some used railing and I am unfamiliar with manufacturers and quality. I am currently looking at rexroth (Bosch) rails. They have some discoloration on one of the faces of the rails. Looks like it may be rust or something else. I dont believe that the surface is rough in the areas the bearings are going to make contact with but any advice on how to choose these rails would be greatly appreciated. If these dont pan out for some reason there is a used set of THK rails that may work but they only have three. I need four for my build so I dont know exactly what to do here. The location of the rails are about two hours away form where I live so i can go and see them and test them out. Is there a way that I can measure the rails with precision equipment to ensure they are worth buying? Should I take some calipers or other devices to help ensure these are still within machining specs? Any advice on how to choose the rails is greatly appreciated.

For the movement of the axese I am using DMM Technologies AC Servo kit. The motors are 750 watt and specs can be found on this page: http://dmm-tech.com/Files/dmmmaxs14a_p.pdf

I have not yet decided on Ballscrews. I would like something that is better for precision and accuracy more than speed. I dont know if I need a low pitch in the ball screw in combination with the motor kit I am using etc... I need advice in this area as well.

My current budget and design are in choosing the rails at this very moment so I need help most in this are. Motors, ball screws, and spindle can hold off but if you have information and would like to contribute in any area it is appreciated. Criticism positive and negative are all appreciated as it can help me strengthen weak points in this build. Thank you all and I look forward to hearing your thoughts.