bowl saver wll thickness

[Duff Bement]

When useing a bowl saver on wet wood, I read that you use the 10% rule for wall thickness. Example: 10" bowl gets a 1" wall. So does that mean that by the time you are coreing the 6" bowl your your wall thickness only needs to be .6" thick or do you need to keep at about 1" for all the bowls from the orginal 10" blank.

[Bernie Weishapl]

Duff I generally keep my bowl thickness on the smallest bowl at around 3/4". I generally don't go thinner than that. On a 16" bowl I will leave the wall thickness at around 1 1/2" to 1 5/8". I also round the lip so it is not square. David Ellsworth and Mike Mahoney both said if you round the lip it is not as likely to crack. Has worked pretty good for me so far.

[Steve Schlumpf]

Duff - I don't do any coring but do the same as Bernie - small bowls are at 3/4" thick after roughing out. Have to allow for warping or you end up with a bowl that is real thin on 2 sides! DAMHIKT!!

[Reed Gray]

I don't think I have ever thick turned a bowl, and then returned it. My favorite wood is Pacific Madrone. The 10% rule will not work for it. I had a 14 inch bowl finish moving at 9 inches wide by 14 long. Some woods will be like that, and you may have to experiment to see how much movement you will get. Standing dead trees will have less water, and there fore less movement. Trees in the spring will have more water, and more movement, fall/winter trees will have less movement. You can leave the bottoms thinner than the walls as there is less movement there than on the rim, but again, that Madrone can do all sorts of strange things from staying dead flat to warping up a half inch or so.

Ditto on the rounding your rims as the sharp edge will tend to open up quicker than a rounded over one. I always round over the rims as much because I use my hand as a steady rest on the outside, and that edge is like a mini razor saw, and will slice the webbing between your thumb and fingers easily.

You should also seal the end grain at least, and I wrap the rims of mine with the stretch plastic film that you wrap around boxes on a pallet (6 inch roll available at shipping and office supply places). Stretch it out as you wrap, and have about an inch hanging over on the inside of the bowl, and the rest on the outside. I usually go around 2 or 3 times. This compression really helps in keeping it from cracking. Of course, if there are any cracks that you don't turn out, they will open up no matter what you do. Wrapping the rim is some thing that I picked up from the DNA soakers. They wrap the outside of the bowl with a couple of layers of newspaper, then tape it to the rim, after cutting out the paper on the inside of the bowl. Theory is that the inside will dry out first, and as it shrinks, it will pull the outside inwards, so the bowl dries in compression mode. This wrapping, with my thin turned bowls does make a big difference in drying without cracking. It works better than bagging the bowls, and just wrapping the rim with the plastic seems to do the same thing.

I really need to do some testing on thick turned, then returned bowls to see just how much difference the DNA soaking does. There is no measurable difference in drying rates or shrinkage, or cracking on the thin turned bowls.

robo hippy

[Duff Bement]

I don't think I have ever thick turned a bowl, and then returned it. My favorite wood is Pacific Madrone. The 10% rule will not work for it. I had a 14 inch bowl finish moving at 9 inches wide by 14 long. Some woods will be like that, and you may have to experiment to see how much movement you will get. Standing dead trees will have less water, and there fore less movement. Trees in the spring will have more water, and more movement, fall/winter trees will have less movement. You can leave the bottoms thinner than the walls as there is less movement there than on the rim, but again, that Madrone can do all sorts of strange things from staying dead flat to warping up a half inch or so.

Ditto on the rounding your rims as the sharp edge will tend to open up quicker than a rounded over one. I always round over the rims as much because I use my hand as a steady rest on the outside, and that edge is like a mini razor saw, and will slice the webbing between your thumb and fingers easily.

You should also seal the end grain at least, and I wrap the rims of mine with the stretch plastic film that you wrap around boxes on a pallet (6 inch roll available at shipping and office supply places). Stretch it out as you wrap, and have about an inch hanging over on the inside of the bowl, and the rest on the outside. I usually go around 2 or 3 times. This compression really helps in keeping it from cracking. Of course, if there are any cracks that you don't turn out, they will open up no matter what you do. Wrapping the rim is some thing that I picked up from the DNA soakers. They wrap the outside of the bowl with a couple of layers of newspaper, then tape it to the rim, after cutting out the paper on the inside of the bowl. Theory is that the inside will dry out first, and as it shrinks, it will pull the outside inwards, so the bowl dries in compression mode. This wrapping, with my thin turned bowls does make a big difference in drying without cracking. It works better than bagging the bowls, and just wrapping the rim with the plastic seems to do the same thing.

I really need to do some testing on thick turned, then returned bowls to see just how much difference the DNA soaking does. There is no measurable difference in drying rates or shrinkage, or cracking on the thin turned bowls.

robo hippy
Sorry , no Pacific Madrone in Minnesota. Do you finish sand your bowls right away? To what grit? Maybe that warping thing would be cool to try.

[Reed Gray]

Wet sanding is a mess, and heating with a blow dryer is slow, and risking cracking from drying too fast. I wrap them, set them on the floor for a day or 3, then up on a wire rack. 1/4 to 3/8 thick are dry in about 10 days. The problem is with remounting them for sanding. I use a recess. I need smaller jaws for sanding, and use an extended set on my smaller Vicmark. You don't need a killer grip for sanding, and if you wiggle it around a bit as you tighten, you can move the now ovaled recess till 4 jaws are on it. The problem is with lathe speed. It really helps to have a lathe that will go down to 10 or 20 rpm. At 50 rpm, you can not keep your hand or a drill on mildly warped bowl. The older PM 3520A models would do this, but they changed it on the B models. They are worried about the motor overheating. Well, I sanded out thousands of bowls that way, and the motor ran cooler than when turning. They can be reprogrammed to do that, but they hesitate to do it. Brent English helped me change the minimum speeds on my Robust.

robo hippy