Hello Shopbot Friends: I am going back to check the alignment of my PRT Alpha.

1) Using my 8 foot level, I have checked for variations in the height of the top edge (contact surface for roller bearings) and I have found some gaps that are .005" or more, but all are less than .010". The manual says look for light between the rail and the straight edge, but it doesn't give any acceptable tolerance (assuming it can't really be +/-.000"). But in the gaps that I have, I can see light.

Most of the gaps are between the 3/4" bolts that secure the X rails to the frame top. And because the 8 foot level reads dead level, I am calling the gaps dips.

Should I file the entire rail to bring everything down to the dips to fix this? That strikes me as a murderous proposition. Should I try and put big metal shims/wedges under the centers of the dips? The instructions only show shims under the mounting bolts. And that is how I adjusted the rails when I set up my machine. Or are my gaps so small that they will be inconsequential?

2) I went to check the "squareness of the X rails" by measuring the diagonals...…… One diagonal measured 185 3/8", the other measured 185 1/2". I remeasured two times and I got the same readings.... (The thought of loosening one side to move it, and then re-adjusting everything else makes me blanch.... I seem to recall that when I originally set up my machine, I had the x rails initially squared, until I went back and made all the other adjustments, and came back to check, and all of the other adjustments had put the x-rails out of square.....
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3) I measured the straightness of one X rail, and using a .004" thick wire drawn taught and spaced 1/2" away from each end of the X rail on machined brass spacers, I was able to straighten the first X rail to deviations of less than 1/64" of an inch. So this adjustment was easy to make and went very well.

4) I then adjusted the opposite X rail at every 3/4" bolt, and was able to adjust it to 78 1/2" as close as I could measure with my tape measure and reading glasses.

So, do I have to go and fix 1 & 2 before I move on to the X car, and then Z axis????? For all I know those readings are great, or they may be terrible...……..

Your experienced opinions are appreciated. Thanks, Chuck