"Jim Chandler" wrote in message
news
SNIP----------------
This may be considered by some as silly, but have you considered
mounting something like a Dremal with a saw blade on your cross-slide
and using the saw to slice out the fin areas while you turn the lathe
chuck VERY slowly, by hand even? That should relieve any problems
with digging in and will allow you much more control over the whole
process. Just a thought.

Jim

Actually, what will work better - I've done it to make very fine features in
ebony, is to use one of those high speed carving tools - mine is 200,000
rpm - it's like a cheapened dental drill - put a straight sided bur in it,
set the lathe to turn medium slowly and then slowly advance the tool
(running, of course) into the work to the desired depth. I cut some fins in
ebony that were about .020 thick with this method - it puts almost no load
on the material. you could use a ball ended burr if you wanted a rounded
bottom to your grove - get the burrs free from your dentist - that's what I
do.