Are Y-Axis and X-Axis perfect 90 Degrees?

I recently did the full maintenance on my OneFinity X-50 including cleaning the ball nuts on both of the Y-Axis rails. When I put them back together I ensured they were in the exact same place on their respective screws so that the X-Axis was a perfect 90 Degrees to the Y-axis.

What I notice is that when I home the Y axis, the distance to the silver guide is different on one side to the other by exactly 1/16. The gap is obviously different which is what made my pull out my caliper. I have tried to realign them again by loosening the X-Axis from the Y, manually turning the screw until they are perfectly lined up but when I hit home again, I am back off by the 1/16" of an inch. Should these two numbers in fact be exact? See the pictures below to further understand my question.

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I would measure to the block not the linear bearing, as the bearings may be inserted into blocks at varying distances.

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Same result, still shows a difference of 1/16" of an inch. I did run a quick G-code on the X-Axis and it does seem to be 90 degrees. I am just not sure why these two measurements would not be dead on.


When I took the (2) M5 screws off the tops of each Y block, I noticed that there was the potential for a bit of adjustment of how far apart the blocks could be. This would not be much, and I think that when they are assembled onto the tubes there is a recess inside that the tubes can be pushed against - I think this would make for repeatable assembly of the rails. I am curious, what measure do you get between the Y axis blocks, and is it the same on the left and right sides?

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I noticed that same thing when I was putting it back together after cleaning the ball screw that the X axis could slide slightly left to right and still have the bolts still catch so that the X block is not sitting perfectly flush on one of the Y axis blocks.

It looks like from the block on the bottom of the X Axis left to right is 37 3/4".

From the block on the Y axis it is 37 13/16.

My problem seems to be the distance of the Y blocks from the end on each side. I moved the gantry out further to make it a little better visual.

On the right side, I see, 5 1/32". One the left side, I see 5 3/32. See the pics below.

I did another test. I went into settings and set the zero-backoff on Motor 1 to 1/4. I saved the settings and homed the Y axis. Once it homed, I checked the measurement on the left rail, it was right on 1/4. On the right rail it was 3/16.