Wall thickness

[Chris Hachet]

I have been turning bowls and spindle projects out of dried wood and have recently started turning green blanks.

For bowls about 5 0r 6 inches across...or maybe 7...I am leaving about 5/8 to 3/4 wall thickness when I am coating them with sealer and putting them up to dry for final turning.

Too thin, too thick, or just right?

Chris

[Dave Fritz]

I'll just throw out that for me it depends on the wood. Some wood that warps a lot it's sometimes hard to have enough wood to finish turn. I think having the same thickness is important. It also depends on the size and it sounds like you're making some small blanks so it maybe ok. All you can do it try.

[Chris Hachet]

I'll just throw out that for me it depends on the wood. Some wood that warps a lot it's sometimes hard to have enough wood to finish turn. I think having the same thickness is important. It also depends on the size and it sounds like you're making some small blanks so it maybe ok. All you can do it try.

Fair enough. Old growth Oak so hope it is OK.

[Dennis Ford]

I think you will be OK on most of them. I don't have a lot of experience in this size although have twice turned many that were larger. Rough-out thickness is a balance between having enough to turn round after drying and leaving it too thick which causes cracks. With some woods there is a lot of room between these extremes, with oak there is not much room between too thick and too thin.

[Chris Hachet]

I think you will be OK on most of them. I don't have a lot of experience in this size although have twice turned many that were larger. Rough-out thickness is a balance between having enough to turn round after drying and leaving it too thick which causes cracks. With some woods there is a lot of room between these extremes, with oak there is not much room between too thick and too thin.

What woods are more forgiving?

[John K Jordan]

What woods are more forgiving?

Most species will warp significantly. Eastern Red Ceder is one that will warp less. Sassafras is another. (Look at the shrinkage numbers in the online Wood Database.)

Both Red and White Oak can be challenging - you might leave the wall plenty thick, at least until you've done some and gain experience in how they warp when drying. After you do a few dozen judging the wall thickness should become easy.

This year I again auctioned off a number of roughed-out bowls at our annual club wood auction. Some were 7-8" in diameter, some considerably larger. As I picked up a dry roughed bowl to offer for bids I'd look at the wall thickness and tell the audience if I thought the wall thickness would be a problem. Some were obviously turned too thin when green to complete - a quick measurement with a ruler or calipers can tell for sure.

If you do turn one such that after drying and warping it's too thin to complete, all may not be lost. Depending on the shape of the wall, you can most likely cut away some of the wall near the rim until you get into the place where the wall starts to curve in more towards the center - the radial wall thickness is probably wide enough there to turn a shallower bowl.

But something to think about - the practical difference between leaving the roughed wall thicker instead of thinner is just a longer drying time. This, of course, assumes the wood dries without cracking, sometimes a problem with Oak. I've had good success by coating the entire roughed bowl with AnchorSeal to help it dry slowly.

Another very useful and underused method that has an extremely high success rate is to boil the roughed bowl before drying. There have been threads on SMC that discussed this. You can read Stephen Russel's excellent articles "Boiling Green Wood to Reduce Drying Degrade (Part 1 and 2)" on the Internet Archive here (be patient, it's slow but worth it):
https://web.archive.org/web/20171003...-articles.html

Instead of rough-turning, some people simply turn the bowl to final thickness when green, sand, and prepare for a finish. Since the wall is thinner even problem wood is more likely to dry without cracking (as long as the base is not left too thick!) The bowl will still warp, of course while drying, but a lot of people like the warped look. It may require flattening or otherwise managing the foot so the bowl will sit flat on the table.

JKJ

[Chris Hachet]

Thanks for the detailed reply.

Going to try the boiling route on a few bowls and see what happens.