First, get yourself a chuck so you don't have to screw into the tenon. If you're turning green wood (sounds like you are) then if your walls aren't close to uniform thickness then the bowl is probably going to warp. Once it dries, remount and turn to final thickness.
Glidden, your tenon should not be bottoming out in your chuck. The face of the jaws need a flat spot to register against and your tenon should be shy of the bottom of the chuck.
That bowl was perfect right up until that last cut...
Last edited by sawdustfactory; 09-12-2011 at 03:14 PM.
Reason: added more