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I have been hollowing for many years, and I have always hollowed with
handheld tools. I am familiiar with the variety of hollowing systems on
the market, and the high prices associated with them, and an engineer
by nature. I took a long, hard look at the problems that are solved by
hollwoing systems, and I boiled it down to two simple things: keeping
the cutter level and on centerline and measuring.
I
think that most of the systems are pretty overpriced for the problems
they solve, so I set out to make a DIY version of a hollowing system. I
added the extra contraint that I could not buy anything to support this
project. Phase I is complete and I have met the stated goal. I now have
a setup that overcomes keeping the cutter level and on centerline
(measurement is still manually done, laser forthcoming in Ver 2)
Anyone
with the usual workshop equipment can make this project, and it will
only take about 1 hr. The supplies needed were in my case offcuts and
leftovers from 15 years of shop time, but if you didn’t have anything,
I suspect you could make this for $20.
I will start with the
easy stuff. The handle for the setup is a piece of quartersawn white
oak. I had slabbed the pith out of a piece that I turned many years
ago. The center slab contains 2 quartersawn sections on either side of
the pith that I always remove and stack for handle material, since the
quartersawn lumber is the most stable. This piece was a shelf support
in my firewood pile for at least 5 years, and air dried enough that I
thought it would do the job. Surfaced on a 6” jointer on two sides, and
planed parallel then ripped on the tablesaw- all that remained was the
hole for the boring bar. I’ll come back to that in a bit.
I
chose MDF for the support, frankly, because I had it. With the handle
being about 1.5” thick, I needed to put the hole at 8” above the ways
(swing of the lathe), which meant my platform needed to be 7.25”. A
sheet of MDF is .75”, one top and bottom equals 1.5”. That makes the
ribs 5.75” If I wanted to do it from scratch, I would double up the top
and bottom of the box, and triple the ribs. If you are going to build
something, why not overbuild it?
Oh, yeah, cause I didn’t want to spend any $$$...
Glue
and screw the box together. It is no mystery how this is done, but you
do have to countersink the screws through the top and bottom so that
everything will slide nicely. The box is about 9”x 24” across the top,
which is plenty big enough for most sized forms. I cut the corner off
of it because it was poking me in the ribs. If I was doing it again,
I’d mount the outer rib flush.
Attaching the box to the lathe is
simple. There is a runner that I made from a scrap of white oak that
you can see in one of the pictures. It is about 6” long and fits in the
channel on the lathes ways. You need to make the upper part of the T
sllgthly (1/16”-1/8”) lower than the lathe bed surface so that it can
clamp on the ways when the bolts are tightened. I drilled 2 holes
through the box and the runner in the center and on the left section of
the box. The runner holes have also been countersunk to make sure that
the bolts clear the ribbing. A stack of washers and a nut hold
everything together. Everything gets tightened to the lathe with a
ratchet, and you don’t have to go much past snug because there is so
much surface area.
I put a drill chuck in the headstock of the
lathe with a bit that matches the diameter of the boring bar I want to
insert into the handle. Using a piece of MDF standing on edge against
the side ot the drill bit, I establish a parallel line on the support
box. I clamp a temporary fence to drill my hole in the handle by slowly
pushing the flat oak board against the spinning drill bit. My hole is
now parallel to the support table and the edge of the board. I hand
drill a set screw hole in the top by eyeball, and tap it with a
standard bolt. I will likely replace this with a wing nut bolt so that
I don’t need tools to remove the bar.
In addition to this bar
set-up, I will be drilling other holes for other diameter bars shortly.
Simply by removing the set screw and replacing it in the right spot, I
should be able to accomodate 4 different sized bars with one setup. A
lathe innovation was the plane handle, which gave me a comfortable grip
to maneuver. As mentioned earlier, a laser measurement system isn’t
going to be far behind. Having a wooden handle to mount it on will make
it pretty easy.
First test drive is also shown. In one of the
pictures, you will notice that the lathe is running at 1000 RPM while I
stood back and took the picture. It’s a little bit slower to cut a
vessel because a lot more gotes into switching tools and cutters than
handheld, but the cutting is done withoutany stress or concern. There
is almost no feedback at all from the tool, so I think you almost need
the laser to measure or risk cutting more vessels in two pieces. The
vessel in the pictures was 2.6 ozs finished, and was probably not any
different than what I could have done by hand (very carefully).
Everything you need to build one is sitting in the pictures I’ve attached. It ain’t rocket surgery…
-- Steven
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