Quote Originally Posted by JAZZCNC View Post
But how do you know the first rail is striaght.???

I wouldn't waste any time setting the second rail without the gantry on the machine. Set the master rail straight and parallel to frame then run set slave rail using gantry running up n down feeling your way along as you tighten up the rail. . . Feel for binding is a very good guide in setting up.!

Dean, how do I make sure one rail is straight without buying a proper striaght edge? My frame is not straight enough to align the first rail, or at least I don't think so as it's just plain 100 x 50 x 4mm steel, with any sort of accuracy?

I was thinking of getting some of my 10mm thick Ali and using the milling machine machine as much as I can down one edge and then turn it round and then using my edge finder set it parallel again and machine the rest to give a straight edge. Would this do?