Quote Originally Posted by Jonathan View Post
Sliding carriages along the rail gives some indication of the straightness, but very little indication of the twist.
He's right, I forgot about that. Neil just go and buy a straight edge I remember putting one across the top of my rail bearing beams to find they were leaning out slightly. This was due to the welding process but the epoxy job brought it right again. I did however put the straight edge across the top of my rails once fitted to ensure they were still level. Obviously if they are out and you bolt down the gantry cross member there will be a lot of stress put on the Hiwin bearings.