You might be thinking that segmented turning uses a lot less
wood compared to
conventional turning because there is very little hollowing involved.
You would be wrong. In conventional segmented ring construction, many
board feet of good wood goes into the trash. Many years ago at an AAW
symposium, Mike Shuler, a well- known woodturner from Santa Cruz, California,
demonstrated making a bowl with very little waste. He had advanced a
technique based on construction methods used in the salad bowl industry.
Shuler also credits Dale Nish, in his classic book Creative Woodturning,
for describing the technique of stacking angled rings band-sawn from
boards to create a bowl shape. This is a great example of how sharing
ideas leads to innovation and the whole field of woodturning advances
one more step. That is not to say that we should all copy each other’s
ideas, there is a big difference between plagiarism and what Shuler describes
as, "spring-boarding from an existing concept." With Mike Shuler’s
encouragement, I will describe the basics of this ingenious technique.
I offer it so you can use the basic technique and possibly take another
step in a new direction.
Instead of cutting, gluing, and stacking individual rings, I will glue
together two large half-rings and then band-saw angled rings that will
be stacked into
a bowl shape. I chose a board of straight-grained purpleheart about 5-1/2 inches
wide by 30 inches long. Using my miter saw, I cut 40 segments with a 4.5° angle
on each side (8o times 4.5° equals 360°). I cut the pointed ends of the segments
less than 1/4 inch wide. Before cutting the segments, I laminated pieces of maple
veneer and thin ebony together in order to create 20 splines that I will glue
between every other segment. For the other 20 seams, I cut the same size spline
from solid holly. These unglued segments and splines are shown in photo 11-42.
Sanding segments of this size presents a challenge because of the length of the
glue lines and the short length of the wood grain. Just a little bit of sanding
heat will warp the surface. Actually, just releasing wood tension by cutting
such short, wide segments can result in some warping. It is certainly tempting
to glue without sanding, but I know I can improve the glue lines, so I sand.
First, I changed the paper on my disc sander. Sharp, fresh sandpaper will reduce
time on the disc and therefore reduce heat build-up. A dry-fit of the segments
confirmed that my cuts were right on and that very little sanding would be necessary.
I decided to freehand-sand half of the seams and then glue those 20 pairs together
with a laminated spline in between (photo 11 -43). To minimize warping,
I sanded the segments in stages, just a little sanding followed by cooling time
I sanded the next. After a couple of very light sandings, the joints were ready
for glue. I performed the bright light check on each seam and waited for any
sanding heat to dissipate before gluing each of the 20 pairs. Never attempt to
glue warm segments, the glue will set too quickly and you won’t have enough alignment
time. Perfect glue joints are vital, one bad joint and the whole project is a
loss. Unlike other ring-construction where there is an opportunity to replace
a bad ring, with this technique replacing a single defective ring is not an option.
article by Malcolm Tibbetts is excerpted from The Art of Segmented Woodturning.