How do you repair a shrunken turned bowl?

I rough-turned a "green" (undried) cherry bowl, coated it with paint, and set it aside to dry for a year. When I got it out to finish turning it, the tenon was oval-shaped due to shrinkage. How can I finish turning this bowl blank when my four-jaw chuck won't grip the oval tenon securely?
—Chuck Perkins, Ithaca, New York

That will often happen to green turnings as they dry to a stable moisture level, Chuck. But it's no big deal—as long as the wood has not cracked across half or more of its diameter. (Better to toss it in that case.) You simply start by turning the tenon (or recess) round again. Here's how.

Open the jaws of your chuck as wide as possible, but no wider than the bowl's inside bottom diameter. Place a piece of router pad or anything spongy inside the bowl to add grip, and then trap it against the jaws. Slide the tailstock over and secure the bowl, applying pressure against the chuck with the live center. With your lathe turning about 200–400 rpm, check the bowl for wobble. Loosen the tailstock's live center and readjust the bowl slightly to remove any wobble; then retighten.

Use a bowl gouge or square-tipped carbide tool to lightly remove material until the tenon is round again. Flatten the bowl's bottom so the jaws will have good purchase on both surfaces. With that done, lock the tenon in your chuck's jaws and finish turning the bowl to shape.