Self correction, updated for today. Although the rails seemed a while back paralel enough, they are not. I have a 1-1.5 mm error on a 1.5 meters run. Anyway, I.ll take the y axis apart in the next days, and assuming you are in my shoes, and you plan to allign the y axis from scratch, in what manner would you do it? Where to start first? Paralel, perpendicular, coplanar? In what order? And how would you do it? The method, please. :)