One more, if you tighten up on a piece of bar stock and you can grab it by hand and move it around. You have a worn out chuck!
A couple of things I look for in a chuck, 1) dings, gouges, broken out places, drilled holes that shouldn't be there.
2) how shiny is it? Is it freshly ground all over? Been polished with a buffing wheel? Bead blasted? Electrolysis used on it?