Next is to make the small maple bowl where I will show
how the black lines are made. Most of
the process for turning the bowl is the same except for some changes to help speed up and improve
accuracy of the layout. This starts with
me making a layout guide for the reference cuts for each sized bowl. Since this is the small bowl the small layout
guide is used. In the photo below each
graduated step is laid out with its corresponding cut depth.
Before I used a fractional caliper to frequently measure
the depth of the cut until it got to the required depth which works OK. However, this method can be prone to error
since the measurements are almost all in 1/32” increments and the dial is only
labeled every 1/8”. This means every
time a measurement was taken which is often as I got close to the final depth,
I had to be careful to double check the reading. While no errors were made it sure would have
been easy to make one and with 12 of these bowls to make the odds of making an
error are pretty good. My solution is to
switch from a fractional caliper to a digital caliper set to read in thousands of
an inch. One other change simplified me
knowing how close I was to the final depth.
Rather than measure the depth of the cut then mentally subtract that
number from the desired depth to get how much deeper the cut needed to be the
caliper gets set to the desired depth then the readout is zeroed. That’s been shown in the top photo. The red arrow shows the line I will cut to
and its depth now shows up on the caliper as a negative .656 inches. Now when the cut is measured it will show how
much deeper I have to go rather than how deep the cut is. When it reaches zero it’s perfect but in
practice, I will stop a few thousands short as a cushion. You can always remove material but once it’s
gone, it’s gone and that’s a problem.
The bottom photo shows the completed cut. From here I work to the left cutting each
step to the depth listed. Process is a
lot faster and easily more accurate with less chance of error. Once all the slots are cut it’s the same
process to blend and fair the outside profile.
Once the profile is done the feature black lines can be
added. That starts by measuring down
from the where the finished top will be to the center line. With that as a reference one line is added to
either side. Scoring
the far left or top line is next shown in the top photo. The scoring needs to be really accurate so
there is virtually no room for error. To
help me out I put on my jeweler’s magnifying headset. The right line gets scored next as shown in
the bottom left photo. Last is to cut
the center one. It’s done last so if
either the left or right line scoring is slightly out of place then the center line can
be adjusted so it looks centered. If all
is well the lines get cut deeper as shown in the bottom right photo. If the spacing isn’t quite right some small adjustment
can be done by nudging the cutting tool to the left or right to even the
spacing out.
Making the just cut grooves black requires no special
skill or exotic equipment. The top photo
shows what I use, a wire wrapped around a piece of wood and held at the other
end with a pair of locking pliers. To
use the lathe is set at about 1,000 RPM’s depending on the diameter of the
bowl. The wire is then held in the
groove and friction does the rest burning the groove black. It may take a little practice to get evenly
made lines but that’s all there is to it.
The bottom left photo shows the first line done and the right shows all
three done. Now there is a little
yellowing on either side of the lines due to heat discoloration but that will
get sanded away later in preparation for finishing.
Here are the medium and small maple bowls with the lines
burned in. The bottom line follows the
same procedure as the top three with one exception. When cutting the bottom line, the parting
tool needs to be held at 90 degrees to the inside curve it is cutting
into. If you try and cut 90 degrees to
the bowl’s center axis then the tool will skate down toward the bottom of bowl
giving you a nice spiral cut. With the
lines cut there is still a lot to do starting with hollowing out the bowl but
for now I am going to go ahead and turn the large maple bowl next so I have all
three done.
After the large bowl’s profile is cut the next step is to
start hollowing out the inside of the bowls.
This starts with turning a 2” diameter tenon (red arrow) on the bottom
of the bowl. The bowl shown is the large
maple bowl but this process will be the same on all.
I don’t think that I have included much detail on the
4-jaw chuck used on the lathe so will give a brief bit now. Up to now the small jaws have been used shown
in the left photo. In this case they go
inside a hole in the top of the blank and are expanded to grip the inside of
the hole. When hollowing the bowl out
the outside of the just cut tenon will be gripped by the medium set of jaws
shown in the right photo.
Here is what the bowl with its tenon looks like held in
place with the 4-jaw chuck. Process is
to lightly clamp the bowl in place then bring the live center that’s in the
tail stock up to the center of the hole drilled in the top so the bowl’s axis
is aligned with the lathe’s axis.
Next Up – Hollowing Out the Bowl, Competing the Base
& a Problem
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