The x-axis may go to infinity in a math classroom...

But not in the real world. I was trying to machine a 10 inch long piece of acetal yesterday, and I could not figure out why the Mill was getting confused about where X=0.  The answer was pretty simple: I was reaching the end of the actual x axis travel, and while the controller kept incrementing X, there was no actual movement. So when it started to go back to X=0, it was actually starting at X=9.