Turning a segmented bowlThis bowl started with my experimenting with figuring out how to glue conical segmented shapes, or splayed miter joints, as I like to think of them.
I made this test piece out of some nice oak, so I could then try to make a bowl out of it.
The tricky thing is how to mount it for turning, and how to add a bottom. Because the precision of this shape was less than perfect, I figured my best option was to turn the inside bottom edge perfectly round and conical and match that with a turned conical "plug".
But I don't have a lathe chuck for mounting a shape like this.
Once the cone was turned, I had to get the plywood off again. I used a thin saw blade in the table saw and cut all around. I had to cut the narrow edge of the workpiece back a little anyway, so I wasn't wasting any material.
I didn't want to make the bottom of the bowl out of a solid piece of wood, because, with seasonal shrinkage, that might cause it to warp or pull away from two sides of the rim. So I made a sandwich of three layers, with alternating grain directions. It's hard to see the wood with all the clamps on it.
When I made my plywood for the bowl lids this way, many people suggested using some sort of press for the glue. But I much prefer individual clamps. That way, I can be sure that pressure is applied everywhere.
I found I didn't have the rim on as straight as I would have liked, so I added a shim on one side between the faceplate and the bowl to offset the crookedness a little.
The inside is mostly round, except for two joints around the rim and the circular joint between the sides and the bottom. Fortunately, I have lots of thickness left, so I can afford to turn it down some more.
I don't like wood turning much, but this part was fun.
A good solution that people have pointed out is to glue on a piece of paper to the bottom of the bowl before gluing on the extra piece. The paper is strong enough for turing, but the bottom can still be pried off with a chisel, essentially splitting the paper in two.
But my bottm was glued on solid. My first thought was to maybe build a bandsaw jig to cut the bottom off. My homemade bandsaw has enough headroom to make this doable.
I wouldn't have tried this sort of thing on my homemade jointer when I first built it, because I didn't trust it right away. But it has served me well for a year now, without exploding. The jointer only has a 2" (50 mm) diameter cutter head, and a relatively narrow opening around the cutter head, so I was able to plane the bottom off the bowl without a problem.
After several passes, checking that the bottom is still level. I put the flat bottom on the jointer table and spun the bowl around while watching the bowl's rim against the fence. If the bottom was crooked, I would have had to do a tapered cut to correct. That would have involved slightly lifting one side of the bowl as I passed it over the jointer.
After the jointer work, I had a bowl with a perfectly flat bottom. But I wanted the bottom to be slightly hollow. The solution would have been some large faceplate chuck to hold the rim of the bowl on the lathe, but I don't have such a chuck.
So I decided to carve it out on the table saw. I attached a back-stop to the fence, and raised the blade to about 2 mm above the table...
I had to take several passes, each time moving the back-stop back a little to carve out a sufficiently large area.
The turned bowl, seen from the top. Note the circle of grain going at 90-degrees in the bottom of the bowl. The way I had turned it, I went completely through the top layer of my three layer sandwich for the bottom. If I was doing it again, I would have made the top layer thicker so I wouldn't end up going through it.
That circle of perpendicular grain is slightly off center. That's because I had mounted the bowl slightly crooked to compensate for the fact that I glued the rim on slightly crooked.
Because this is a bowl, I should expect that at some point, somebody might put a salad or something else wet into it, so I needed a finish that wouldn't let water penetrate. Oil-based finishes are best for this. I don't use oil-based finishes much, but I still had some Varathane finish left over. I originally bought it to varnish some canoe paddles two years ago, then used it again to varnish the tables for the jointer and then the wheels and frame for my bandsaw/sawmill
I always use oil based finishes outside. This time, in front of my new shed. That way, I could just put the piece inside the shed to let it dry overnight.
Some people really like to use these "painters triangles" for supporting work. Personally, I just use some triangular rails and put the work on that instead. They sometimes leave a slight line on the workpiece, but there's no risk of leaving a divot in it either. Whatever line might end up on it can be scraped off with a chisel. Sometimes I cut notches in the edge of the rails, but usually I don't bother.
I'm sure there's better varnishes for bowls, but the Varathane I already had, and looking around on the net, people don't seem to be worried about it being poisonous.
Segmented bowl turning
Beri's homemade lathe
Making coat hooks
on the lathe
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