Kevin Cleary wrote:
Does anybody have a good method for finishing off the bottoms of bowls.

No one so far has mentioned vacuum chucking which is another option to
consider, though it is expensive and I have yet to bite the bullet

If you want to reverse turn, the technique you use depends on the rim
design. For example, a bowl with a natural edge cannot be held with
anything that grips around the rim. A bowl with an in-turning rim
generally cannot be held in a standard cole jaw. I have made special
grippers for one of my popular bowl designs, but it's a lot of work for
a one-off.

try some of these google searches:

doughnut chuck

longworth chuck

vacuum chuck

cole jaws

--
Derek Andrews, woodturner

http://www.seafoamwoodturning.com
http://chipshop.blogspot.com - a blog for my customers
http://www.seafoamwoodturning.com/TheToolrest/ - a blog for woodturners