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Basic
Frame-Miter Segmented Bowl Construction
This
article was reprinted with the permission of Kevin Neelley. For
more information about him and this technique you can visit his
website.
The bowl that was designed in Designing
a Segmented Bowl Using a No-Math Method and Designing
a Segmented Bowl Using Your Computer is shown below. This article
is intended for the beginning segmented woodturner. I have attempted
to show the photographic sequence of bowl construction steps with
descriptions. There are many different techniques for constructing
and turning a segmented bowl. This article shows the way I decided
to make this bowl, but I might make the next one totally differently.
Click on any photo for an enlargement.
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This is the newly completed segmented bowl. It was made from
maple and purpleheart with holly and blackwood veneer details.
It was constructed from 12-sided frame-mitered rings, except
for the base, which was a solid disk.
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An inside view of the new bowl. It was completely finished on
the inside. |
Cutting Segments
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These nine maple and purpleheart boards were cut using the
filled-out "Segmented Bowl Design sheet" from my
article, Designing
a Basic Segmented Bowl Using a No Math Method. Since maple
is cheap, I decided to save time by cutting all the maple
boards the same 22 inch length, so there will be some maple
scrap left. If I made the bowl entirely from expensive exotic
wood, I would have cut the board length for each ring as per
the Design sheet plus one inch.
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This is the frame-miter table saw sled I used to cut all
the segments for this bowl. The sled plans can be found here.
Before making any saw cuts I made sure that my table saw blade
was perfectly vertical, which is very important.
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Using the #2 ring segment board as an example, the first
step is to pencil mark one board face (as in the photo to
the right) so the segmented ring can be assembled with each
segment's grain oriented in the same direction. Before cutting
segments, I fully raise my table saw blade to keep from excessively
cutting into the fence.
After marking the board face, the next step is to cut off
the end of the segment board using the miter sled. Then, flip
the segment board edge-for-edge for the next cut, and for
each successive cut. Note that during a cut there is a tendency
for the saw blade to push the segment board to the left, which
makes a wavy cut. Gluing a strip of fine sandpaper to the
fence edge helps hold the board in place.
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Using the Design sheet outer segment width for ring #2, mark
the 1-3/8" width dimension on the #2 ring segment board,
as in the above photo. Align the mark with the fence sawcut.
Butt the stop board against the segment board and clamp the
stop board tight. Make sure there's no chips or sawdust between
the segment board and the stop board or fence. All 12 segments
can now be cut. During the cut, the cutoff segment must be
held tight against the fence and stop board. To prevent possible
kickback, hold the cutoff segment tight until the saw blade
has been fully withdrawn from the cut. Check for chips and
sawdust after every cut. If holddowns are used, they should
be used on both the segment board and cutoff segment.
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This photo shows how the the 12 segments have been sequentially
cut from the #2 ring segment board. This is not a normal construction
step. Normally, I just cut each segment board and put the segments
into individual piles. All the segment boards should be cut
at this time. |
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All the segments boards have been cut into segments. I have
loosely arranged each stack of segments into rings held with
a rubber band. This is not a normal construction step. Note
that the pencil marks on each segment are facing the same way
(either up or down). I normally start gluing the segments as
soon as I finish cutting them. |
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To show what all the segment rings look like at this stage,
I have rubber-banded all the cut segments together and stacked
the rings like they will look when glued. This is not a normal
construction step. Note that each ring is turned 1/2 segment
from the ring below it. |
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This is the waste wood left over from cutting the segments.
Since maple is cheap, I had cut all the maple segment boards
the same length of 22". If I had made the bowl from exotic
wood, such as cocobolo, I would have cut all the segment boards
1" longer than the calculated Design sheet length.
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Gluing the Segments
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I used a clean and newly-sharpened sawblade so none of the segments
needed sanding. I have glued pairs of segments together. To
glue the segments, I spread glue evenly on the mating surface
of one segment, then mate the segments together, rubbing the
segments together to distribute the glue, then I set the segments
down carefully on a sink cutout. Glue doesn't stick to the formica
on sink cutouts. If the wood end grain seems to excessively
absorb the glue then more glue should be applied. In the photo
above, I have rubber banded the segments of rings #8 and #9.
Rubber banding gives the tightest possible joints. I usually
only rubber band the most visible joints, like the lip ring.
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This photo shows segment pairs being glued together. For a 12-segment
ring like this one, I don't glue all pairs together because
I want to end up with two half-rings. Later, I will sand the
butts of the half-rings to make the half-rings fit perfectly
together. |
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All of the half-rings have been made. Now it's time to sand
the ring butts. I use a 12" disk sander to sand the ring
butts. I used to use a 6"x48" belt sander to sand
the ring butts. At one time I used sticky-backed sandpaper attached
to sink cutouts or glass sheet (very flat) to sand the ring
butts. I'm always on the lookout for easier ways to do things.
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To keep from accidentally sanding the ring butts too much, I
put pencil marks on the butts like in the photo above. The idea
is that when the pencil marks are just sanded off, the
butt is flat. Sometimes I rotate the sanding disk by hand when
there's not much butt material to sand off. Never over sand
the butts. Over sanding will make the ring oval, which can really
badly affect bowl wall thickness. |
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This photo shows the pencil mark is halfway sanded off. So,
there's a bit more sanding needed to flatten the ring butt.
Every ring butt should be pencil marked and sanded at this time.
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All the ring butts have been sanded. The half rings have been
glued and rubber-banded together. |
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Now, one side of each ring should be sanded flat. Be careful
and don't over sand One side of every ring should be sanded
at this time. The other side of the ring will be flattened on
the lathe. If you have a thickness sander, you can save
time by using this tool to flatten the rings. |
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I sometimes use a Wagner Safety Planer (purchased at Woodcraft
Supply) chucked into my drill press to flatten the other side
of each ring. This operation also planes the ring sides parallel.
Sometimes I'll skip the planing step. Instead, I'll glue one
ring at a time onto the lathe faceplate and flatten the ring
on the lathe. This second method can make the bowl assembly
process take longer, but if I'm making several bowls at once
(and I usually am), the total assembly time for all bowls can
be much less. |
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All of the segmented rings have now been flattened. The next
step is to glue the rings onto the faceplate. |
Gluing the Rings
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The faceplate I'm using for this project has lots of waste wood
on it, at least 4 pieces from past projects. When I cut a bowl
off the faceplate I always leave a little bit of the wood behind
(for no particular reason). To make the new bowl more interesting,
I'm adding contrasting veneer in four places (refer to the finished
bowl at top of this page) consisting of white and black veneers.
I used my drill press as a veneer press for gluing. |
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The purpleheart base disk is being glued to the faceplate. The
white and black veneer pieces have already been glued to the
base disk. |
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I have turned the base disk (ring #1) round in the lathe.
The next step is to attach ring #2 to the base disk. To center
ring #2 on the base disk, use the following procedure:
1) Measure the smallest inside diameter of ring #2.
2) Spin the base disk on the lathe and draw a circle on it
about 1/8" smaller diameter than the ring #2 inside diameter
dimension.
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3) Test fit ring #2 and the base disk. Use the circle on the
base disk to center ring #2 by eye. The circle on the base disk
should be smaller than the ring #2 inner diameter so that the
circle mark is not obscured by glue oozing out from under ring
#2. If everything looks good then glue ring #2. After gluing
two rings together, before I clamp the rings, I usually let
the glue set up for a few minutes so the rings don't shift.
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Ring #2 is being glued to the base disk. If you're really
nervous about the rings moving, wait a few minutes after clamping
to check ring alignment. You should still be able to get the
rings apart, although you might need to use a sharp chisel
to break the glue bond.
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The next step is to attach ring #3 to ring #2. This step
is nearly identical to the previous step (ring #2 to base
disk):
1) Measure the smallest inside diameter of ring #3.
2) Spin ring #2 on the lathe and draw a circle on it about
1/8" smaller diameter than the ring #3 inside diameter
dimension.
3) Ring #3 needs to be turned 1/2 segment rotation
from ring #2 so the split lines of the ring #2 segments are
in the middle of the ring #3 segments. So, make a pencil mark
halfway across two segments on ring #2, on opposite sides
of the ring from each other. Two corners of ring #3 will be
lined up with the pencil marks.
4) Test fit ring #2 and ring #3. Use the circle on ring #2
to center ring #3 by eye. If everything looks good then glue
ring #3 like the previous ring.
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Kevin Neelley
www.turnedwood.com
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