Hy, I looked around the shop, thinking to make a jam chuck, but didn't seem to have anything that would work for a 10+" bowl with a fairly wide bottom. I hear ya on the warning about the thin-kerf saw, those things are great, but it's really easy to nick "good wood" with them (or good skin
). Have you seen Doc Green's book
"Fixtures and Chucks for Woodturning: Everything You Need to Know to Secure Wood on Your Lathe"?? It's a great book for this kind of stuff. A whopping $15 on Amazon. Pulls together stuff that's scattered across the universe and puts it in one well-written and well-illustrated volume.
When I jamb Chuck bowls I use wood about 3" in diameter mounted in a Chuck.
It is hollowed a bit on the end and has rounded edges.
A firm pad is required between the bowl and the Chuck. Folded paper towel works great, piece of leather, thin fun foam.
Tailstock in the center of the tenon ( I leave the point from when the tenon was last trued). brings the bottom of the bowl against the Chuck and pad.
The curved bottom of the bowl almost self centers on the rim of the Chuck.with the pad between the bowl and the Chuck.
This makes a wood sandwich with the pad on two slices of wood. I have never broken a bowl using this approach.
Holding a bowl by the rim or jamming it on the rim only works for bowls with fairly thick walls and fairly flat rims.
The jamb Chuck below is almost universal. It will work for natural edge bowls, thin walled bowls, curve rims.
Before putting the bowl on the jamb Chuck, I measure the bottom thickness with calipers and transfer the measurement to vernier calipers.
The thin metal sticking out of the vernier calipers is the distance from the tailstock center to air inside the bowl.
Once on the Jamb chuck I can turn the tenon away, shape the foot, hollow the foot and use the vernier caliper to judge the thickness of the wood.
I use my bowl gouge, small bowl gouge and spindle gouge
With this method you cannot make a funnel unless you decide you have more wood that the vernier calipers tell you.
I end up with a small cone of wood pressing the bowl to jamb Chuck. This cone gets real weak as the point gets thin.
So no bevel pressure. Turn on the top of the tenon if you let the tool get pulled under the tenon it will break the tenon. Pushing the cut into the point of the tenon will cut it free or break it.
I usually turn the point to about an 1/8" thick turn the lathe off and use the spindle gouge to cut through the cone a 1/8 inch proud if where it joins the bowl at 3rpm.
The 3 rpm is how fast I turn the bowl by hand. This leaves a little button 1/8" tall X 1/8" wide that sands off in seconds.
You can also build a donut Chuck with something like the Jamb Chuck shown (or PVC pipe) mounted in the part of the donut that attaches to the headstock. The the clamping preasure of the donut would damage the rim or break the bowl.