Need some help

[Don Meyer]

I have started final turning of some roughed out blanks that I treated with DNA and let dry for several months. I have been having some problems with some of the rims in that they are of not equal thickness the whole circumference of the rims. Any advise on what could be causing the problems I am having. On some of them it is quite noticable but on others you can only detect it by close examination.

[Dennis Ford]

Sometimes turning the outside round will release enough stress that the bowl will warp a little. Then when you turn the inside, wall thickness is uneven. If you are trying for a thin wall this can be a problem. If there is enough thickness available, you can alternate cutting outside / cutting inside, a couple of times and get a more even thickness.

[Leo Van Der Loo]

Are we talking after you returned the bowl or before you returned the bowl ??
As wood shrinks in width/thickness and not the length the wall will be thinner after drying on the side of your bowl, even more so if there's sapwood at the sides and heartwood on the ends of the bowl, this all applies to a dried bowl before returning it.
After returning a dry bowl the difference in the wall thickness will only happen if there is movement when returning the bowl, as you remove wood from the walls the equilibrium of the wood is changed and the wood will move to equalize that again, then turning the inside (if you did the outside first) you are turning not the same circle as the outside one, it is also the reason to not try to go to the outer edge again after turning the wall thin as we know that the shape has changed while turning, if you do that you would remove even more wood from the places that have moved inwards.
I hope I didn't confuse you with my explanation, so I ask clear as mud ??? ;-))

[Ken Fitzgerald]

Don,

That is not all that unusual. As wood dries...even after being treated with DNA it usually warps. The solution for this is to leave the wall thickness at 10% of the diameter of the roughed blank....so if you have a 10" bowl...leave the wall and bottoms with a 1" thickness ....DNA and let it dry. This will usually leave you enough thickness you can turn it back to round after it dries and have a consistent wall thickness.

[Bernie Weishapl]

I also would like to know if this is happening while you are turning it on the lathe or is it before you start turning it. One thing I have found way back when is if you don't get your tenon true and a flat surface for the shoulder of your chuck to seat against you will see that happen one side slightly thinner than the other because it is not running true.

[Don Meyer]

thanks for the hints and comments. I was having the problems on returning the bowls after I had turned the outsides and was doing the insides of the bowls. I let the bowls dry outside in my unheated shop for about a month and then took them inside to my basement. I believe that they didn't dry very much since the weather has been very cold in my area and the month they were in my basement was not enough to dry them. It was very probable that they were warping as I was returning them and that accounted in the differences in the thickness of the rims. Thanks for all your help.