re: Ringmaster Bowl

LBD, normally with the Ringmaster you mount the board by drilling a 1/2" hole in the center and you have to plug the hole when you are done.  I really hate that so the last two bowls I have made this way I used a glue block to mount it on the lathe so that I do not have a big belly button staring at me in the bottom.    You can see the glue block still attached on the 2nd picture.  I just use a hot glue gun to attach it.  It holds so well it can actually be a little bit of a PITA getting the glue block off.  Using a little denatured alcohol to soften the wood helps but on this one I didn't want to risk that messing up the the finish that I had already applied on the sides of the bowl. 

EDIT to add:  I use a tap that matches my spindle threads to mount the glue block on the lathe. 

BTW, here is a good video for a technique and jig for cutting bowls from a board without buying a Ringmaster.