I use armbraces extensively, many hollow forms per week. When I see
discussions like this I am reminded that they are possibly the most
misunderstood tool in the woodturning universe. You *CANNOT* reach far
over the toolrest with those things. With the standard Stewart setup, 8"
deep is about maximum for my comfort level, and I'm good at it. I have a
15" extension that I add which gives me around 33" in front of the handle,
and with all that I figure 12" deep is pushing the limits. When I saw
Clay Foster demonstrate a 30" deep hollow form, he had a bar about 10
feet long that was HEAVY. It gives you an idea of what is really needed
to counterbalance the forces working against you. Use the Stewart tool
within it's limits and it's a wonderful tool. Try to do something you
shouldn't, and you get in trouble.

Kevin's remark about just don't get a catch is not merely a wisecrack,
despite his well deserved reputation for wisecracks, it's for real.
Scraper tip hollowing tools realistically should absolutely never get
catches. All you have to do is keep the tip above center. Then the
rotation of the piece is trying to force the tool away from the wood, not
into the wood which is where catches come from and what can happen when
the tip is below center. This assumes you have drilled a center hole,
make your cuts from the center outward, and don't jam the tip into the end
grain. When sweeping across the bottom, you have to keep the tip below
center, of course.

Arch, post a picture of your plumber brace when you get a working model
you like, I'd love to see it. best wishes,

-mike paulson, fort collins, co