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Options on rotary carving


I’ve worked with chisels, but the delicate undercuts are getting to
where I need to look seriously at rotary.

Currently, I am carving in marble. The grains are very very small, so
I don’t need to worry about individual grains chipping out as a
defining limit on scale (more an issue in Danby marble than Rutland
or Carrara; if it’s even an issue at all). The stone is soft, so
resistance is minimal; though there are some hard spots every now and
then. Future endeavors will be engraving glass, carving semi-precious
gemstones and pearl cameos, embellishing wooden handles with
scrollwork, etc.-- some of those things are best suited with gravers
or a combination gravers/rotary, some might benefit from a different
beast of rotary. So I’ll ignore those for now and get what will work
for marble.

I’m thinking that marble is so soft, that diamond burrs will be
wasted on it, indeed, may just clog up.

I’m thinking carbid burrs, perhaps designed for aluminum with few
and wider-spaced flutes to take a larger bite and with room for more
material, rather than small flutes that may overheat or stop cutting
when the dust doesn’t want ot escape.

I’m thinking maybe glass-cutting bits, essentially carbide spade
bits reground for a variety of profiles or even homemade steel ones
if I can get the symmetry right.

Where do you get your burrs? Should I get steel or carbide; is
either reasonably resharpenable and how?

I’m thinking a Foredom, the L series with just 5000rpm for slower
speed. I’ll be removing a lot more material than the other extreme,
a 400,000rpm turbocarver-type rotary, is made for; though I
appreciate the possibility that a slower-speed, higher torque tool
might also catch some?

Are there alternatives to the Foredom L that you recommend? How
about old belt-driven dental drills; are the handpieces more self
supporting, giving more delicate control?

Or finally; how about building my own antique-style bow drill?
Slowest of all, won’t catch or get out of control easily because I’m
directly controlling the power and have perfect feedback, not just a
delayed response with the footpedal; but I also have only one hand
to control it.

let me know your thoughts,