here is a cheap way that I have used to turn the bottom of my bowls
(natural edge) I usually have a tenon on the bottom and mark the center
with the skew I have a piece of 3/4 inch ply 9 inch round mounted on
the chuck I then put the bowl in a small rubber ball and place it up
against the flat surface of the ply in the chuck, bring up the tail and
center into the bowl bottom apply pressure to the ball turn by hand to
get to turn round and take off the bottom as far as I can reach. The
rest ( about the size of a pencil) I sand off by hand and finish. Speed
is important and getting the bowl to turn round is good but I have done
this many times with good success. Gordon