Brad Vietje
Hey Henry,

You've gotten some great info, but I think a few assumptions have been made, and a few critical bits are being left out.

I may repeat other comments, but I'll try to include the missing bits:

1. Many turners start a bowl between centers, so you can make small adjustments to the position and tilt of the rim and foot for the best results (usually to balance figure, growth rings, sapwood, etc...). When forming the tenon, leave a small stub at center with the mark made by the tail center for use later.
2. If you start with a screw chuck or a face plate at the rim of the bowl, you give up some of the control over these factors, and you would not have a tenon with a mark from the tail center. Even if you don't start between centers, you can bring up the tailstock specifically to make a mark for re-chucking later.
3. I start all bowls between centers, and always leave the tail center impression for re-chucking later. I rarely leave anything inside the bowl, unless I turn a recess or ledge for chucking in expansion later.
4. To re-chuck an oval bowl, either set it over the chuck and hold it in place with pressure from the tailstock (as Doc suggests), or make a few discs or short, wide, cylinders shaped to be held in the chuck jaws for this purpose. If you have round discs of different diameters that fit the "wood-worm" or screw chuck adapter that comes with most chucks, you can quickly spin one on that's a bit smaller than the rim of the bowl (the disc tightens up against the jaw faces), set the bowl over this disc, bring up the tailstock, and away you go.
5. The bowl is held very securely in this way, and if the support inside the bowl is wide enough, you should be able to finish turn, sand and polish the outside, as well as true up and re-shape the tenon for gripping later, before going to the inside of the bowl.
6. Grip your now-perfectly-shaped tenon, and finish turn, sand and polish the interior.
7. Reverse turn again with the disc of wood and the tail center -- this time being careful to pad the contact area between the disc and the interior of the bowl -- and shape the final foot, removing evidence of chuck jaws, and carefully turning the bottom of the foot down to a little nub, which you can remove off the lathe.
8. With practice, a long bevel, and a steady hand, you can get the little nub down to less than 1/4", and on smaller pieces with good balance, down to about 1/8". Thus nub is snapped off or cut away off the lathe, and touched up with a little hand sanding.
8. A nice trick to learn -- and a nice little show-off step a lot of experienced demonstrators use -- is to turn the nub away completely, holding the bowl up against the wood disc with steady pressure from the bevel of the tool! It helps to have a long bevel (pointy tool) on a detail or spindle gouge, fairly low RPM's, and even a slightly convex bevel so the wood is burnished, and not scraped up by the pressure from the bevel against the foot. You need to be able to turn the lathe off with the hand that's not holding the gouge for this to work!

If you get used to starting bowls between centers, you'll always have a little index mark to use when re-chucking later. The rest just takes practice. It may seem like a lot of steps, but they go quickly and naturally once you turn the various disc sizes you need. If this process seems too slow, this is where production turners and those with more money than patience (IMHO ) use a vacuum chuck. They are incredibly handy, but not required to do this sort of reverse turning.

Safe spinning,

Brad Vietje
Newbury, VT