With the outside of the bowl shaped to your preferred profile we need to setup the bottom of the bowl so that it can be reattached it the lathe. This will enable the removal of the material from inside of the bowl. This is called Reverse Chucking and a Four Jaw Scroll Chuck used to attach the bowl to your lathe with the inside of the bowl facing the tail stock. The bottom of the bowl has been turned flat and square to the lathe; turn a Spigot of about ½ inch high on the bottom of the bowl. I prefer the use a large diameter Spigot and then create a recessed dovetail cut in the spigot of about 3/8 inch deep. The diameter of the dovetail needs to be within the travel range of you Scroll Chuck Jaws. For the heavy bowls I prefer the recessed dovetail; this method is stronger. Smaller bowls you can turn with a smaller spigot and hold the outside of the spigot.
Remove the bowl from the lathe and remove the face plate and attach the chuck in the dovetail recess. Best way; is to attach the chuck to the bowl before you connect the scroll chuck to the lathe, this assures a better alignment. Then connect the chuck to the head stock. If the chuck is not set properly in the dovetail recess the bowl will have a wobble. A slight wobble is OK because the bowl will be re-tuned after it is dried. The jaws are numbered on the scroll chuck; mark the bottom to the bowl to correspond to one of the jaws so it can be re-chucked in the same position after drying.
After the bowl has been attached to the scroll chuck and connected to the head stock of the lathe. The Natural Edge Bowls have an uneven surface and will cause a lot of stress to the holding capability of the chuck when you begin turning the inside. For safety and to help support the bowl use the tail stock for support, same procedure as in article 2.
Place the banjo in between the bowl and tail stock; with tool rest at the proper height rotate the bowl by hand to insure that the bowl is free to rotate. Using a Bowl Gouge and beginning near the 60 degree cone live center, start carefully and slowing cutting out the inside of the bowl, once you have some depth and cut is even you can move along faster. As you move deeper into the bowl you will have to move the tool rest closer to the surface of your work area. If the any tool is over extended beyond the tool rest it will cause a lot of vibration.
The distance that a tool can extend beyond the tool rest is related to the size of the tool you are using, it's best to follow the manufacture's recommendations. Large diameter tools can extend further beyond the tool rest than a small diameter tool; same with thickness.
The bowl will have to be dried after the material inside the bowl has been removed; this will discussed in the next article. The thickness needs to be about 1 inch thick, sides and bottom except the dovetail recess which should be a greater thickness. At this point much to the weight has been removed and you can with draw the tail stock. The spigot remaining within the bowl can be removed by using a Bowl Gouge or I prefer to use a large Forstner Bit. Using a drill chuck mounted in the quill of the tail stock you can advance the bit and remove the remaining wood; a horizontal drill press. When the inside of the bowl is uniform; use the Round Nose Scrapper to smooth the inside of the bowl.
Attached link is a glossary to terminology for the lathe and associated tools; http://www.turningtools.co.uk/glossary/glossary.html
The next Article we will discuss drying the green wood, reattaching the bowl and completing the final step. We will use a Bowl Gouge, Scrapper, Sand Paper. The reverse chucking using a Scroll Chuck and Vacuum Chuck. If you have any question or comments visit my web site and send me an email. http://www.yourwoodturningtools.com
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