From what everyone has said, and looking into the tools mentioned and
more, I have an impression that the tools that have a 'better result' (
I include safer in that) are essentially a very mechanical construction,
almost similar in operation to the tools on a metalworking lathe, albeit
quite a different construction. i.e. the user is not really a part of
the equation other than for moving the tool.

I have found an interesting design in the poolewood catalogue

http://www.poolewood.co.uk/cgi-bin/s...%3a%2f%2fwww%2
epoolewood%2eco%2euk%2facatalog%2findex%2ehtml&WD= reeks%20dave&PN=Dave_Re
eks_Hollowing_Tool%2ehtml%23aDRHT30#aDRHT30

if the link doesn't work try http://www.poolewood.co.uk/
and search for 'dave reeks'

I think that in the coming months I will be constructing something
similar, combined with the ideas mentioned elsewhere in this thread for
the toolhead design. The most obvious extension of the design would be
to include laser guidance

I wonder if anyone here has tried/used a dual laser design for guidance,
all I have seen are single lasers. My thought is either one vertical
laser which is common and one horizontal both pointed to the tip of the
tool edge, or both from above but at 90 degrees to each other Using this
method the thickness of the form could be determined by how close the
lasers are on the surface

Oooh so many ideas to play with
--
John