The under rails on my 15-21 have wear on them from use before I acquired this press. I can see this pretty clearly and it looks like it’s about .oo5, primarily at the the carriage end of the rails, then it tapers off. What is reasonable to work with when adjusting the carriage bearings? And should I adjust the bearings in that area or compromise between the worn and not so worn areas? This is a big disappointment because this press is in otherwise really good condition.
Set the impression bearings with the cylinder on print positioned in the middle of the bed. Place a 0.003″ shim between each bearing and the rail, tighten snugly to the rail, then roll the cylinder off the paper and it should be about right. It may take a thicker shim, but should be the same for all four of the upper bearings. This can take time and experimentation.