Trouble squaring rollers


I have been stuck for days attempting to get the left & right rollers parallel to the table and each other. Going through the Forums I see virtually no mention of this so I assume that I am missing something.

I am using a slab door as my table. I have used .25" hardwood dowels taped to the top edge and bottom edge of the table and pulled the pipes against them while tightening the XZ’s. I seem to get the rollers close to parallel as measured by placing a steel rule against the roller sides and measuring 18" from the center of the XZ Main (see photo). Yet when I measure across the table the sides are not aligned, one or the other is skewed out by up to 2mm. When I raise the Z sides the rollers skew telling me that the Z pipes are not parallel to each other.

I have reprinted the XZ main parts. I have the large screws in the Z roller assy’s just tight enough to stay against the side plates with very little pressure on the pipes. I have adjusted the 6-32 screws in the XZ’s time and again. I just can’t seem to get the pipes perfectly vertical.

Watching “Old Guy Coding” videos it looked like he had his pipes rubbing the sides of the table, but wouldn’t that impede the belt?

At this point I am stuck. Any advice would be most appreciated.


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Did you remember the spacers in between the pipes?

Can you take some more photos from the sides of you XZ parts? Maybe a pic showing which way they aren’t parallel?

I am not understanding the issue clearly. If you think the sides are not tracking straight measure across at both extremes of the Y plates, that number should be equal (adjusting the X rails in the XZ parts). If it is something else, more pictures would help.

I could be misunderstanding the issue but I have to ask. Is the table square?

Thanks for the replies guys.

The table is square within 2mm over 80”, it is a slab door.

When I got home I measured as Ryan suggests from extremes of the Y plates and they are within 0,5mm. My Z pipes are out of vertical maybe 2deg.

I think I was measuring improperly. As my favorite nephew, an accomplished engineer is fond of telling me, “business school is where engineering students go when they fail sophomore math”. Gawd I love that kid?

I will push on and see what happens. Thanks much for the replies!