This article has been translated from an original one I wrote for the July
2004 issue (no 13) of Couleurs Bois
(French woodworking magazine).
It is the first in a series about hollowing tools. Each article describes a tool
and its use in the making of a turned piece.
The Termite is well adapted for end-grain hollowing. You can
use it cross-grain, but the resulting surface will not be as good.
Shavings will also have a higher tendency to clogging . It performs especially
well in open shapes, flared or straight (box, mortars, vases). In closed shapes,
it's difficult to maintain a good position of the tool. So I have chosen a tall
vase shape, and I found a piece a field maple (acer campestre) which
should suit. Its dimensions are 10*25 cm (4*10"), for a finished piece
which measures 8.5*23cm (3 3/8 * 9"). Take care if you take a log, the pith
can cause cracks and checks problems.
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I start by roughing the log between
centers. You can start to establish the shape, but no need to go too
far, as it will probably be out of round when you will put it in the
chuck. |
I turn a dovetail tenon for the chuck. |
The piece is held in the chuck, but
for the moment, I left the live center for safety reasons. It also
allows to minimize vibrations, which are often a problem with these
tall shapes. I turn the cylinder back to round, and I can start to
rough the outside shape. Speed is 1200 rpm. |
If the shape is flared, you need to take care to leave enough wood at the
headstock side, to not weaken the piece. So here I don't go down to the final
shape, otherwise I will have vibrations problems during hollowing. I can come
back to this part later. (when turning green wood or very thin, it is better to
sand and finish now: thinness or warping would make these operations difficult
later).
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The tailstock is moved away. Don't forget to remove the live
center, it's quite painful when it comes too close to the elbow (and the
position with the Termite makes this kind of meeting quite probable).
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The speed is quite low (700
rpm), the toolrest is set so that the tool is horizontal. I'm
cutting with the small diameter, which is on the left on the picture. I
always start with the ring in vertical position (so it doesn't cut), just
a few millimeters deep in the pilot hole.
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I gently rotate the tool
clockwise. The low side of the ring is starting to cut. The ring's
orientation is "1 o'clock". The more I rotate it, the higher the
cutting depth (and thus the risk of catch).
An orientation around "2 o'clock" is good. |
Once I've started the
shaving, I move the ring towards the outside, by pulling it with my left hand.
This hand is guiding the tool, the fingers maintaining the tool against the
wood while pulling it towards me. |
You always need to start
this way: if you start "at 3 o'clock" (horizontal) the dig-in
is guaranteed. Following this principle, I increase the diameter, but I
keep a margin on the wall thickness, which will be useful for 2 or 3
finishing cuts. |
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I continue hollowing deeper. for a better control, I settle the handle under
my armpit, and use my hand on the toolrest as a pivot point. It allows me to
rapidly increase the diameter of the central hole. Then I start from the
bottom of the part I've just completed to clean the side.. |
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The
commercial shaft works approximately up to 17cm (7") deep without
vibrations, so I take the home made shaft for the end. Once I reach the
final depth, I need to use the other bevel, since the obtuse one prevents
the cut. So I will cut with the bigger diameter side of
the ring. Once again, I start vertically and rotate the tool. With my left
end, I pull the tool from center to the outside. Attention: once I get
close to the walls, the tool with its bigger diameter offers ideal catch
conditions, so I rotate it counter-clockwise to decrease cutting depth and
get a very light cut.
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The edge might have been
damaged during hollowing, so I don't forget to clean it with a sharp
spindle gouge. |
I check that the thickness is what I want. |
Without cutting, I repeat the motion of the final cut, to verify the
toolrest won't disturb me and that my body position is correct, then I execute
one or two finishing cuts from the bottom to the edge, in a continuous, uninterrupted
motion.. No room for a catch there ! |
Now I only have
to sand and apply the finish to the inside. Sandpaper and foam wrapped
around a wooden stick will help reaching the bottom, but take care: the
stick can be pulled off your hand by the spinning vase.
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