"Robin S." wrote in message
...
You could also use some math and calculate some depths for a grooving tool
(say, 1/4" wide if you have a heavy lathe, smaller if necessary) to rough
out the groove. Then file finish. Sounds like a lot of work, but
building/buying a radius attachment for your lathe could cost serious
hours/dollars.

I think I would try something like this. Grind yourself a tool bit with a
round nose and have a radius gage. You now want to cut your radius profile
by eye and checking after each light cut with the radius gage. It would be
slow going but if all you need is one or two this might suit you.

It might also be easier to make your die in sections cutting a quarter
radius on a plates and then assembling the two plates together for use.
This way you could mount a pivot on the tool rest and clamp the tool bit to
swing your arc with a lever.

--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
they come up with this striped stuff.