I use the 40/40 on platters where there is no tailstock in the way and I’m single turning dry wood.
With warped dried bowls. The Ellsworth grind is my choice.
I use the center point in the tenon and do a friction drive jam with the slightly opened jaws of the chuck against the inside bottom of the bowl. Resting on the open jaws is usually rock solid. In the rare case where I sense a tiny wobbly i open the jaws a bit more or close them a bit to find a solid no wobble.
I adjust where the bowl rests on the jaws so that the edge of the 2 high points on the rim are centered(= distance to the tool rest set parallel to the ways) and the 2 low point edge centered.
This gives me the largest bowl I can return from the warped bowl. With this centering I will take equal amounts of wood off the endgrain wall and close to no wood off the side grain wall.
The chuck jaws give a solid drive.
1. True the top of the rim ( flatten it ) with push cuts toward the tailstock. This removes most out of balance part.
2. Return the outside wall foot to rim
3. True the tenon to about 2” ( near the perfect circle) my rough out tenons are 2.5” so the dry oval tenon is about 2.5 x 2.25
Mount in the chuck. Test for tuning true - it usually does. If it is off looses the chuck and turn the bowl as quarter turn tighten and check.n. If that didn’t fix it tap the rim lightly with the lathe running with the tool handle if it runs true tighten the chuck a bit.
If that doesn’t fix it I will return the outside.
Then turn the top of the rim
Then turn the inside.
This thread has a demo video of me returning a really warped dried sycamore bowl.
The August 2015 AAW JOURNAL has great article by David Ellsworth on working with green wood. This is followed by 11 marvelous ways turners turned cracks into features. One of David's themes is that the deck is stacked against newer woodturners successfully working with wet wood. Might be a nice...
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