Linear Pillow Block Slide Bearing Specs. How accurate will my cuts be?

[JimmyL]

Hi Everyone,
I'm currently building a diy CNC router and am having trouble figuring out what kind of linear Pillow Block Slide brand to get. In a set that im currently looking at there are these figures for the tolerances for x y and z movement:

Mx17.5 My6.9 Mz6.9 with rails at 48'' (4ft)

Im currently interested in cutting wood and hard woods with my router but want to move on to aluminum in the future. im ok with tolerances under 0.002" but anything above im not so sure. My 4'x4' frame is made up of 80/20 extruded beams. Are these tolerances ok for the producing accurate cuts without any 'jiggle' in the linear slide system?

Ive noticed other linear systems that have something along the lines of

Mx 4.x My 2.x Mz 2.x

Is there a noticable difference between these figures than the figures above them?

[ger21]

Not sure, but the tolerances on the 8020 aren't that good. Straightness of 8020 is .0125/ft.