This particular bowl was taken from a White Oak with a diameter of approximately 30" that had been taken down for the construction of a new house.
Section the tree into an appropriate size for a bowl. (The length should be at least as long if not a little longer than the diameter of the section.)
Split this section into bowl pieces.
Preparation of this section for a bowl with the back side at the base.
· Cut or flatten a plane on the bark side of the piece
· Mark the circumference of the bowl on the opposite side of the base
· Chain saw the piece into a circle and then chain saw the bark side to balance the blank.
Drill a 3/8" hole on the bowl side. (opposite the base) to screw mount in a chuck and then mount on lathe. ( I use a screw that is held in my One Way chuck and also use the chuck exclusively for the turning and finishing of the bowl. This is just one method of doing the bowl and using faceplates is another way of accomplishing the same task. This is my preference and not necessarily the only way to do it.)
When mounted on the lathe, bring up the Tailstock to firmly hold the piece in place, as we want as much of a safety factor at this time as possible. The piece is still not completely round, even though we did our best with the chain saw it will still be somewhat out of balance on the lathe. Start out at a very low speed and if you have a variable speed on the lathe, bring it up to where it just starts to vibrate and then back down the speed. (With a variable speed there is also the ability to increase the speed and this will sometimes take away the vibrations from the out of balance.) Whether variable, or fixed speed with belts, as the piece becomes more symmetrical, you can then increase the speed.
Once the bowl is formed to its general shape, I then turn a large diameter spigot about 1/4" deep and approx. 4"-5" in diameter that will be held in my One Way chuck. This is flattened and slightly concave if you were going to mount it on a faceplate. (Some people would mount the blank on a faceplate and do all of their work with the bowl facing outward from start to finish.)
I then unscrew the form and reverse it on the lathe, inserting the spigot into the chuck, tightening the chuck jaws and then again bring up the Tailstock while I start the hollowing process of the bowl or form.
Once I have gone as deep as I can with the bowl gouge, I back off the Tailstock, remove the wood cone that the Tailstock was pressing against and finish hollowing the bowl. The walls of the bowl should be approximately 10% of the diameter of the bowl. (i.e. if the bowl is 18" in diameter, the wall thickness should be approx. 1.5" thick) The base can be taken down thinner as the majority of the distortion of the bowl will take place in the upper regions of the bowl.
I then place the piece into a double paper bag or a box with newspapers surrounding it if it is to big for the paper bags. I check the piece on a weekly basis for the 1st 3 weeks, changing the bags if they are really damp or wet and then on a monthly basis after that. Production woodturners have kilns that they use to dry their pieces. (A kiln can dry a large bowl in 30 to 35 days compared to my method which takes anywhere from 3 months to over a year.)
Chainsawing a Circular blank
Good luck in your turning!