I had some LM8UU Bearings here but had ordered some more just to be sure and I'm amazed at the fluctuation in sizes you get with them as well as the 8mm smooth rod.
The smooth rods are all different sizes and while it's by a tiny amount when you add in the LMUU bearings you get a wide range of fittings.
The rods varied from 8.02 to 8.07 so I tried 17 of the bearings on every rod matching up each bearing to each rod to find a fit that didnt grind. I know they are cheap chinese things and should take this into account but it is still surprising me. I'm going to research the performance some of the Ingus drylin bearings.
edit:- I ordered some of the drylin bearings and boy they arent cheap I put them on the x axis but wont be able to really test them until the rest of the items I need to get this thing up and running arrive.
After clamping the bearings into their housing on the X axiz also causes them to become missaligned and to not run smoothly at all. Yikes!
I'm still waiting on some of the small nuts and bolts to arrive and am using some 35mm one I had here already to test everything.
Finally got the X Axis to run smoother.