[snip]
I have a gauge and bleed valve and I wouldn't be without either,
especially
the gauge. Without it you are really flying blind and that might let the
piece go flying too! It is surprising how much leakage you can get through
some open-pore wood if it is thin. Another thing to consider is that the
force is pushing the bowl against the faceplate or drum chuck towards the
rear of the spindle. The only force keeping the bowl from sliding
perpendicular to the spindle is the "friction" of the bowl rim against the
faceplate. If the faceplate is covered with foam then the rim "digs in"
due
to the force and is held securely. The drum chuck likely has the curvature
of the bowl bottom against the chuck so it keeps it from moving.
Billh


As you can probabl;y guess, the faceplate for my vac-chuck is home-made too.
A 19mm MDF (fine at lowish speeds) disk screwed to a 6" faceplate and faced
with 5mm foam rubber. The foam itself is fairly porous, but with the high
air-flow that hasn't proved to be a major concern.

I've even made minor catches severe enough to seperate the bowl from the
faceplate and the high air-flow has sucked the bowl back down, albeit
off-centre. Fortunately, apart from when first learning /how/ to use a
vac-chuck, I haven't had any UFOs but I think that's probably because I've
had to learn to use a light touch rather than any inherent advantages of the
chuck.

For the record, I should say that I'm not advocating my system as being "as
good as any other," just that there are some very cheap ways to make a start
for someone with a little ingenuity. Anyone trying it should keep in mind
that you only get what you pay for. G

I am curious about drum chucks though, having never used one. I assume that
they're like jam-fit chucks where it's best to make a custom one for each
job, unless you've already made one that just happens to be the right size?

- Andy