I build a stock size MPCNC with 304 stainless steel tubing. Not willing to leave well enough alone, I had a desire to increase its length to accommodate larger pieces. I bought some 60" long 3/4" schedule 40 galvanized steel pipe.
The 304 steel is 1.003" and the new tubing is 1.062. That slight change in diameter is very noticeable. The trucks accepted the tubing with some gentle persuasion, but the core needed all of the bearing bolts loosened to the point of floppy and was still a tight fit.
The most notable difference is that the new axis with the new tubing is “bumpy”. The surface doesn’t feel that bad to the touch, but on the trucks it seems to grab a bit. The stepper motors aren’t attached, but moving it feels like the steppy resistance you feel in the stepper motors.
I’ve read the tubing can be sanded with 200 grit to knock it down a bit. I’ll do that, but I wanted to see if there are any other suggestions before I continue on.
(I realize I’m at the cusp of just building a LowRider, and that will be in the cards eventually. But this is where we are at now.)