Coring
The picture above shows a piece of black walnut which after being rough turned was twenty inches in diameter. As a rule of thumb, on green wood, I use a ten- percent figure for the wall thickness. For example, if your diameter is twenty inches, wall thickness should be about two inches. In this case the piece of walnut was fairly dry so it was not necessary for me to make the bowl blanks at the ten- percent thickness. As the picture shows, I marked out all the cuts first, and then cut out five blanks from the one piece of wood. The largest bowl finished out at 19 3/4” and the smallest at 8” in diameter. If you consider the time required to hollow out the inside of a twenty-inch bowl or to core out five blanks, you will see the cost advantage especially if you are buying your wood. Coring is a fast, money saving way to produce more products from the same amount of wood.
Coring is a way to produce more than one bowl from a single piece of wood. It does require some type of coring tool. There are a few different ones on the market, from hand held models on up. I have used a couple different ones. The one that I am currently using is the one that I like the best. It allows me to retrieve bowls from nine to eighteen inches in diameter.