With the bottom half of the bowl glued up it’s time to do
the top half. Here all the jigs are set
ready to start gluing on the segments.
Note that the top half of the bowl is held in place using a scroll chuck
rather than the typical face plate used for the bottom half. In this setup the scroll chuck's the outer black jaws are
adjustable and when tightly closed clamp the piece in place.
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| Ready to Add Segments |
The same process is used to measure, cut and glue the
segments in place as used on the bottom half of the bowl. Here two of the layers are glued in place and
I am ready to start on the third and last row.
Once all three layers are glued up I now have rough blanks
for both the top and bottom. These are
ready to mount on the lathe and begin turning.
I started the rough turning by mounting the bottom half back
on the lathe. Looking at the blank I
thought it looked like a giant cheese grater powered by a 2 horsepower motor
ready to shred whatever it came in contact with, for instance my fingers. So with a face shield on and standing to one
side out of the way of possible flying pieces I started the lathe up. Gradually increasing the speed up to about
500 revolutions per minute I paused to check for vibration and to see if it
would hold together or fly apart. Since
there was no vibration and no pieces flying around I cranked up the speed a
little at a time more and more until I got to just under 1,400 revolutions per
minute. Still no vibrations and once
stopped I saw no visible problems at a speed well beyond what I would be turning.
With that test I was ready to actually start the
shaping. I set up the tool rest, spun
the lathe up to just under a 1,000 revolutions per minute then with a newly
sharpened spindle gouge gingerly started to shape the outside of the bowl. I will say that in the back of my mind I was
thinking that the only thing holding this together was a bunch of itty-bitty
glue joints. The good news is that
everything worked perfectly, the gouge cut away thin wispy shavings with no
drama and no excitement leaving a nice smooth surface. Once I had the outside knocked down to a
preliminary shape I moved to the inside.
This is a photo of the inside turning in-progress. You can see the shavings coming off the tool
and being held by centripetal force against the inside face of the bowl. I would have liked to have frozen the motion
of bowl but now I was turning at slightly over 1,000 revolutions per minute and
even with the photo taken at 1/4,000th of a second the bowl still shows some
movement.
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| Turning Inside of Bowl Top |
With the lathe stopped and all the shavings blown off the
overall rough shape both inside and outside starts to become apparent.
The last step on the bottom half prior to fitting is to take
a piece of sandpaper on a flat board and use it to sand a square mating
surface. This is the glue surface that
will match up with the top half and the two halves need to fit tightly
together.
Comparing the bottom half piece I just finished rough
turning to the unturned top half gives an idea of how much difference there is
between the two.
The glued-up top blank is now mounted on the lathe and the
same process of turning I did on the bottom half is gone through with it. With both halves roughly turned I mated the
bottom half up with the top half to see how they fit together. Here, circled in red you can see that the
piece on the right which is the bottom has a little larger inside and outside
diameter than the piece on the left which is the top. The fix is to take a little more material
off the inside of the top (left piece) to increase the inside diameter so that
it matches the bottom. I will also trim
the outside diameter of the bottom (right piece) down so it is closer to the
top. If bottom ends up a bit larger
that’s not a problem because once both halves are glued up I will do the
outside finish shaping.
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| Test Fit for Mating Top & Bottom Halves of Bowl |
Once I have exactly matched the interior diameter of the two
halves I drilled out the center of the top half which will be the opening at
the top of the bowl.
Here the hole is drilled out, the interior is finish sanded
and I just need to round over the hard edge at the hole in the top. Nearly all of the interior final work needs
to be done now as when the two halves are glued up there is only a 1½” hole at
the top for access. The bottom needs to
be completely finished as the base is solid and there will be no access there.
With all the work done on the inside of both the top and the
bottom I am ready to glue them together.
The numbered pencil lines across the glue joint are my reference marks
to make sure the two halves are lined up dead on when I glue them together.
After letting the glue cure overnight I blended the two
halves together and finished turning the segmented part of the piece to its
final shape.
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| Segmented Part of Bowl Finish Turned |
Next Up – Finishing the Bottom, Top & a Problem
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