Providing pictures for this How To... section has been delayed by our move from Virginia to Kansas in August 2014. I will start to add pictures and diagrams as soon as I can. Stay tuned.
The log bowl is great fun to do as it is the most challenging of the four. This involves hollowing since the inside will be bigger than the effective opening at the top resulting in undercut ends. Sitting on the table, the top opening appears to be pretty big, but when it is whirling around on the lathe, the effective size of that opening is only the size of the shortest measurement between the two top edges.
The secret to the log bowl is the size of the log. You will have to turn a whole piece of log which is longer than it is wide. If the log is about 4” wide, then the length of the log should be about 6” to 7”.
The diagram to the right illustrates the outside turning and the inside turning. It is because the log is longer than it is wide that allows the cut through the sides to plunge down so precipitously rather than smoothly as in the basic natural edge bowl.
It should be noted that wood tends to check from the pith out. I have found generally that the smaller the branch of wood, the less chance there will be of serious checking. Also, fairly thin hollowing helps the wood to dry more evenly, too, which further reduces checking tendencies.
Mount the whole log on the lathe with a spur drive on the headstock side and a live center on the tailstock side.
Once mounted as shown here, carefully round the outside ends of the log. Cut from the bottom to the center and then from the top to the center to minimize knocking off bark. Shape the bottom of the bowl as usual, leaving a tenon for later chucking.
Reverse the bowl and grip in a four-jaw chuck. Start hollowing with a bowl gouge as usual. Be careful to leave a line of bark around the top. Once you have cut as much as you can with a bowl gouge, you will have to switch to a scraper or hollowing tools to complete the task. The good news is that the deeper you go, you will be opening up the sides of the bowl and that will allow you to watch the position of the tool inside the bowl as you turn. Keep the thickness of the sides uniform all the way down to the bottom. You will have to judge how thick to make the bottom, depending on the type of base you want. Sand as you go.