That was my problem, sanding the pen after parted off tended to not stay true and it was very hard to apply and sand CA without blowing thru.
That grizzly chuck looks like the tips might be a MT-0.
One bit of advise I have is to make the center hole after it's all on the live center. Mine was hard, I had to tape the wood to the body and true it up after I put it all togather. Somewhere down the line it had a wobble. I made the base bigger than the head because the live bearing is missing it's seal. I tried to get the bearing out to rebuild it, but failed.