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A Bowl on a Pole Lathe
by
Darrell
LaRue |
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Recall my previous attempt at a bowl on my pole lathe
back in early July. A comedy of errors, truly one of
those "learning experiences" one hears about. Fast
forward a few weeks, and I've had time to think about
what I did right and wrong, and to make a new tool. That's right, he's blaming the tool, folks. Turning
is like that I guess.
A short time (that's Galoot time, not SWMBO time) ago
fellow Galoot Ed Paik dropped off a hunk of freshly cut
maple he had scavenged from his neighbor. I roughed out
a couple of bowl blanks from this rapidly drying maple,
slathered them with wax emulsion, and put them in a
plastic bag to keep them wet enough to work. Time
passed, and my summer holidays approached, and the bowl
blanks grew moldy and ugly.
When I finally got to the cottage (where my pole
lathe lives) the weather was not conducive to spending a
lot of time outside at an activity like operating a pole
lathe. Sitting on the beach drinking cold beverages was
a more proper occupation when the temp ran over 35 C. So I set up the lathe in the "basement" (more
correctly termed a crawlspace in this instance, but tall
enough for a short guy like me) and mounted the Bodger's
Muddle in the rafters above. The basement was a bit
cooler than the Great Outdoors, so I could actually work
on the lathe without expiring from heat exhaustion.
I used the mandrel I made in July (scavenged birch from the firewood pile). A 1 inch hole bored in
the face of the bowl blank would accept the end of the
mandrel.

Note the mould growing on
my bowl blank... turners love this kind of thing, they call it "spalting". With my luck, it'll end up being just plain ugly.

It's just a friction fit, driven with a mallet. This
whole arrangement is then set into the lathe, with the
drive rope around the mandrel. The outside of the bowl
gets rounded off first, using a roughing gouge and a Sorby bowl gouge. I dunno if the Old Guys used anything
like a bowl gouge, but it worked great on the pole lathe
for me. This is where I was stymied last time. Now that
the outside was round, it was time to start hollowing.
And here's the fun part: you can't get too close to
the centre because you need the strength there to drive
the bowl, and if it gets too thin, then that hammered-in
tenon will split that mortise. That's one of those
"lessons" I mentioned earlier...
Now the really funky
tools come out to play. I did a bit of research and
asked some questions on the APT website, and it turns
out I needed a hook tool. Nobody makes these anymore
except a few specialist blacksmiths, which option fit
neither my wallet nor my schedule at this point.
Not being totally useless in the shop, I had made my
own hook tool. I used a piece of a tine from an old
horse drawn hayrake, Dan's Bootstrap Forge (thanks again
Dan!), and a bit of scavenged 2X2 to make my hook tool.
These things are apparently supposed to be used on the
bottom of the turning, on the surface moving away from
the turner. Kind of on the pull stroke. I started out
turning the blank by hand and holding the tool in
various orientations to try and get a feel for what
angle and direction I needed to use to make this weird
thing work.

A few tentative attempts were required before I
gained the confidence and learned the appropriate
technique to get shavings to flying. And fly they did! It was then a matter of working my way down to the
bottom of the bowl. I can't say much about the
smoothness of the surface, but that's likely a technique
problem.
Or perhaps a sharpening issue? There are a lot of ridges in the surface, but no tearout. Hmmm, maybe I
need a selection of various shapes and sizes of hook
tools? ("of course!" mutter the SGFH cronies over in the
corner).
Now what do I do about the core? I can't work any
closer to the centre with my hook tool. That Sorby bowl
gouge to the rescue again! I kept working the core down
until I finally intersected the mortise and the bowl
flew off the lathe. I managed to catch it before it hit
the floor (reflexes still OK so far...). So now I have
some cleanup to do on the inside, and a bit of sawing to
get the base sawn off.


The base makes a handy way to hold the bowl in a vise
whilst working on the last bit of the core. I attacked
the inside of the bowl with a chisel and a hook knife
and very shortly the bottom was smoother than the rest
of the turning. Then I sawed off the waste from the
bottom.

And it's a bowl!.

I packed it in a bag of fresh shavings to slow the
drying process, and that's where it sits now, waiting
for the first crack to develop...
Darrell
Oakville ON
September 2006