Kevin's Woodturnings
  

COMPOUND-MITER SEGMENTED BOWL CONSTRUCTION  

These scans of a segmented bowl that was constructed using compound miters and frame (flat) miters and the construction steps I used to make it. Click on any of the photos for an enlarged view.

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I made this bowl from locally harvested curly ash. The ash was a very nice wood to work with. The red lines are African padauk wood. The central ring is ornamental banding veneer.

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The padauk line pattern goes completely through the bowl. I tried to save some of the natural defects in the wood. These features give the bowl character.  The finished bowl is 9-1/2" diameter x 5" tall.

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My design says I can make a bowl from a board 48" long x 5-3/4" wide x 3/4" thick. One end of this board has a big unusable knothole in it, so I cut off that end of the board.

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I ripped the two boards for my two compound-mitered segment rings. The board for my top ring is 28" long x 2-1/2" wide. The board for my bottom ring is 28" long x 3-1/8" wide.

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One of the boards is on my compound miter sled. I am cutting the segments for a 12-sided, 70-degree incline angle, 10 " diameter ring. Note the C-clamp stop.

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The 12 segments for one compound mitered ring are cut out. The segments are cut consecutively from the board, just like it appears in the photo. For illustration, I have reassembled the cut pieces into the board.

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I am now cutting out the flat mitered segments for the bowl's central ring. The photo shows my flat miter sled. The sled fence is set for a 12-sided ring.

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All the bowl's segments are now cut. There are two compound mitered rings for the bowl's top and bottom, two flat mitered rings for the bowl central ring and lip ring, a base disk, and the leftover board scrap. Not much usable scrap!

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I am gluing together the segments for the central ring and the lip ring. I use rubber bands to hold pairs of segments together. I don't use anything to clamp pairs of glued pairs together, just Titebond II glue. With a little glue between the segments, I rub the segments together and carefully set the segments down on the sink cutout.

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This photo shows padauk veneer being glued to the compound mitered segments. I rubber-band the segments to a plastic block to keep the veneer flat while the glue dries. Glue doesn't stick to the plastic block.

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This is the veneer trimming operation. All of the compound mitered segments have padauk veneer between them. Adding veneer doubles or triples the time it takes to construct a bowl, but I think it's worth it. Sometimes I'll glue several layers of veneer between segments.

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Now I'm gluing the compound-mitered segments together to form the bowl's top and bottom rings. The central ring and the lip ring are finished.

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To make the rings come out perfectly, I make half-circle rings, then sand the butts flat. The two half-rings will fit together perfectly using this method. I use a 12" disk sander for small rings and a 6"x48" belt sander for big ones.

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I use a faceplate with a thick wastewood block attached. The new bowl's base disk and disks of padauk and blackwood are ready to be glued to the faceplate.

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This photo shows the clamping setup (using my drill press) for the faceplate and base disk. Also shown is how I rubber-band the half-ring to the sink cutout to keep the veneer flat while the glue dries. 

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Here are the two completed compound mitered top and bottom rings. The topmost ring will be the bowl's bottom ring. I pre-planned the knot hole to be located on the top ring so it will be more visible. I like wood to look like wood - knots are great!

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I use a Wagner Safety Planer (from Woodcraft Supply) to flatten the compound mitered rings. I have found this method to be the safest of all the methods I've tried for flattening rings. It's also very fast.

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I usually flatten both sides of each compound mitered ring with the safety planer. 

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This is the clamping setup for gluing the rings together. I don't put much downward pressure on the compound mitered rings. The veneered joints aren't strong until the next ring is glued on, rotated by 1/2 segment..

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I put the assembly from the previous photo in my lathe to flatten the face (true it up) and turn the perimeter round. I use the rounded ring perimeter to help keep the next glued-on rings concentric.

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Veneer is being glued to the trued up compound-mitered bottom ring. I make the veneer pieces in 1/4 circle arcs to save wood waste.

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The veneer ring is finished . Now the central ring is being glued onto the assembly. This knot hole will be hidden by the ornamental banding.

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Veneer is being glued to the flattened compound-mitered upper ring. Again, I use the drill press to keep the veneer flat while the glue dries.

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The compound-mitered top ring is now being glued to the assembly.

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The final veneer that goes between the compound-mitered top ring and the lip ring is being glued into place.

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The lip ring is being glued into place. The bowl assembly is now complete.

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The complete assembly is on the lathe. Now it's time to round it out.

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Another view of the same.

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Still another view.

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I have completely rounded the bowl. I round the outside, then I round the inside. I cut extra material out of the inside to get my desired thickness. I use gouges and skews on the outside. I generally use a hollowing tool and several different kinds of scrapers on the inside.

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I have cut a shallow groove in the central ring and glued in the veneer banding strip. I held the strip in place with rubber bands while the glue dried.

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The final lathing of the base disk is now complete. The outside surface of the bowl has been lightly sanded, then burnished with a Scotch-brite pad. The next step is to part the bowl off the lathe by cutting through the waste block on the faceplate.

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