Originally Posted by zoltan
I'm installing a new 4" spindle in my mini lathe. Once it's installed, should I take a very light facing cut on the surface of the spindle to make sure it's square and flat?
Not at al! At least not at first.
First do nothing until you have checked radial and axial runout with known good dial indicators. If these are excessive still avoid machining.
The first thing to check would be you bearing installation on the spindle.
In an ideal world the bearings would be shrunk fitted on the spindle. Done right this should result in a bearing that is properly square to the spindle.
In a nut shel don't touch the flange with a tool until all other issues are eliminated. Even then do nothing until reviewing everything again.
I realize that this is Chinese machining but the flange should be pretty good right from the factory. It would be the last thing to touch in my mind.