Even though I've been up and running for some time I'm still a newbie in many ways. I noticed that a slot running x to x was slightly wider than a slot cut with the same code running y to y. I decided to adjust my motor tuning in Mach to make them the same. Nearly drove me crazy looking for a setting that would produce a given travel. Of course, that gets to repeatability. So I decided to focus on that first. I securely fastened a digital caliper to my Y rail and opened it as wide as it would go. Then I slowly jogged down until my carriage began closing the caliper. When it got a little above 4" I zeroed the Y and zeroed the caliper. Then I gave Mach the command to move to minus 4". After each cycle I wrote down the numbers. Then I returned the carriage to Y zero, zeroed the caliper and repeated the cycle. I did this five times and got the following numbers: -3.9765, -3.9775, -3.9760, -3.9755, -3.9775. Subtracting the smallest from the largest gave me a difference of 0.020". I wonder how that stacks up in the world of CNC routers in general. I would appreciate any feedback.

I don't have an answer, but I am curious - how does this compare to your X and Z ? The reason I ask, is that assuming you used similar assembly methods, this would give an indication of whether you have 1 axis better / worse than the others.

I think you missed a zero. When I do the subtraction I get just 2 thousands of an inch. You wrote 20.

I need to run this test too. I have no idea how repeatable my machine is.

You're right. I was trying to get the post up so I could go to bed. Would've been twenty TEN thousands. That's better. But-- I'm pretty sure my caliper was slipping. When I got ready to do the X axis I noticed it was lose. So I'll have to start all over.