Turning the top half follows just about the same process
as the bottom half. However, in looking
at the previous post I think there were some intermediate steps in turning the
inside face of the bowl that I should have included. Having a nearly identical piece gives me that
opportunity to fill in that gap in the process.
I am going to pick up after turning the outer face and
right after mounting the blank using the large jaws on the chuck. Here it is ready for me to start turning or
dishing out what will be the inner surface of the bowl. The 2½” drilled hole used to hold the blank
in the chuck using the intermediate size jaws to turn the outside face of the
bottom is clearly visible.
Leaving a flat surface about 5/8” wide for gluing the two
halves together I started turning away the inside of the top. My goal here is to mirror the outside curve
leaving a wall thickness of about 3/8”.
If you are really, really good you can probably gauge the thickness by
feeling both sides. Me, I rely on a gauge
to get that constant thickness. I have
three different ones but here is what was used on this bowl.
Rather than take off material in layers all the way
across the face from edge to center I work to a finished depth from the outside
in. That’s because as material is
removed you decrease structural integrity which makes the piece less stiff
which can allow the piece vibrate via harmonic chatter giving you a turned
surface with all kinds of hills, valleys, ridges and even spirals. Below are two photos showing how I worked my
way toward the center roughly a third at a time.
Below on the left you can see that when I get right at
the center, I leave a little nub. The
top of this nub is the bottom of original drilled 2½” hole. It acts as a reference so I can tell how far
I have dished down into the blank. Once satisfied with where the turned surface
is, I take the nub off and finish sand the surface as shown in the right
photo. Don’t worry about the little hole
in the center it’s going to go away soon.
To make sure the glue band at the edge is square with the
bowl axis I start by marking it up with a pencil. Next, using a straight board
that has some sandpaper glued to one end I hold the bare wood up against the
right edge and use the sandpaper end to remove any irregularities and flatten
the band. When done I have a good glue
surface square with the bowls axis.
Well, almost square as there is a tiny bit of taper toward the inside
since there is only sandpaper on one side.
That’s not a problem because I want the outer edge tight and can live with a hairline
crack on the inside. If I wanted it
truly square a second piece of sandpaper would need to be added to the opposite
end of the board.
The last step on the top for now is to drill the center
hole. Here you can see where the Fostner
bit has just started to break through the other side. It will be finished when I flip the blank
over, remount it on a different set of jaws and finish turning the top’s
outside.
With both the top and bottom blanks finish turned on the
inside and mostly turned on the outside below are the two halves in the same orientation
as they will be when glued together. On
the left is the top while on the right is the bottom.
Setting the top on the bottom looks like this. The bottom needs have final shaping done to
the foot and the top needs to have the foot completely removed. Also, the outer edge is a little fat so once
the halves are glued together that will have to be refined. Speaking of the edge I am thinking about
doing a turquoise inlay band where the two halves come together. No decision on that but I am considering it.
Now it’s time to switch out the large jaws on the scroll
chuck and go to the extra-large jaws.
Once that’s done the bottom blank is mounted and the finish turning done
to the foot. The work here included
making the foot about a half an inch smaller in diameter, cleaning up the
inside of the foot to remove the hole I had drilled earlier and adding a
shallow recess to delineate the rim the piece will set on when done. The left image shows what the foot looked
like earlier, right after I had drilled that hole and the right shows the
finished bottom.
Next up is the top going though a similar process with a
slightly different result as there is no need for any of the foot to
remain. Left photo is top mounted in the
extra-large jaws before I started turning and the right photo is when the turning is completed.
Stacking the top and bottom halves together like they
will be when done looks like this. In
looking at the profile I can see the top curve needs some more help. It is not as smooth as I would like. If you look about an inch in from the outside
edge there is a little bump that needs to be smoothed out. I am not too worried as once the two halves
are glued together, I will need to finish the edge and its transition.
This completes the Phase 1 turning which is as far as I
can go for now. Next is to stain and
finish the completed inside faces of both halves. No way that can be done later through the
small opening in the top half.
Next up – Inside Finishing & Making a Live Center
Cone
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