Your Inside Bowl technique

[Roger Chandler]

16" and 9" deep. That's a bird bath not a bowl. Well, a small swimming pool anyway. A bowl that size and diameter will almost force you to take the thickness down an inch at a time. I don't believe the "mass at the bottom" theory is as important as keeping as much thickness immediately below the inch you are working on. I also try to keep the finished thickness in proportion to the bowl size. Coincidently, I am hollowing a 16" cherry bowl now. It is a twice turned bowl. Last evening I took the entire bowl down to one inch and left it over night to stabilize. I had it in a cold room in storage. Between warming up in the shop and the stresses I probably relieved removing the uneven thickness, it is bound to move some more. I don't expect to make it much thinner then 1/2". I know that even taking the thickness down an inch at a time will get invite chatter unless I keep the tool really sharp and take very thin cuts until I am over half way down the side. depth. I try to match the cuts so as not to leave ridges or bumps even though tiny bumps sand away far easier than chatter, tear out or gullies. Those I avoid like the plague. Of course, by the time you read this you are probably already eating a gigantic salad from the bowl. have fun Roger, I'm sure it will turn out great.
faust

Faust.......I did exactly what you describe with thin cuts and sharp tools.......one exception.....I went about 1-1/2" on the steps as I hollowed it out. It is currently still on the lathe......no time to work on it today, but it is at about 5/8" thickness, and I have an itch to take it to 1/2" with about 2 more light passes. It has been through warming/cooling cycles in my shop for the last 3 days, so I know what you are saying about the bumps, etc. It is pretty true already, but I just want to make some final shear cuts on the outside to smooth and a couple of light passes on the inside.....its going to be a looker, I think!

I think this will be my last project on my G0698.......our turning club bought it from me earlier this month, and will deliver it to them when they get the new electrical circuit run for it, and I will be awaiting my new G0766......hopefully it will arrive by the latter part of February [fingers crossed!]

I will have to go small with my Delta midi 46-460 until my new green monster arrives!

[Thomas Canfield]

In response to a couple of posts about returning the 16" or so size, I have found that truing up the outside, and then truing up the inside will result in the outside being out of round due to reliving stress when cutting down the thicker sections truing the inside. I will jam the rough bowl inside against opened jaws of chuck, and with live center in dimple left in original tenon center, return the tenon and a section of the bottom to clear the chuck and headstock when mounted in the chuck. I then use a block to pad the live center to provide additional support to hold the bowl in the chuck and true up the outside with the bottom still facing the headstock. It is not the ideal way to cut, but does allow a more uniform thickness than would otherwise be possible. On 18"+D bowl went over 1/4" out of round after the inside was trued up. That is all the more reason to have a full 10% of diameter wall thickness on the rough piece. After getting the outside and inside trued up, then turning to final wall thickness is done in stages to help reduce the bowl going out of round and wall thickness variation.