Howdy All,
Since things appear a little slow here - maybe folks are distracted by the coming holiday weekend - Let's be safe out there - don't M-80 any fingers or poke your eye out with a sparkler as you'll need those for turning - otherwise hope all have a sunny, pleasant 4th!
Awhile back I looked into messages about turning bone and even messaged a tad with Arch- as I recall - about the characteristics and qualities of bone as a turning material. My project was turing a small ring that would become an insert in a candlestick. This is what I encountered:
Finding bone: To make the rings, I needed bone that had a predetermined outside diameter with enough wall thickness to true it to the proper outside and inside diameters. That turned into a challenging task. I looked at many places, including my grocery store for "raw" bones and the pet and feed stores for the dog chew bones. I found the best course was to paw through the bins at a couple Petsmarts for the bleached, non-filled bones. These are clean and white with no need to do any boiling, scraping or bleaching. Try to pick out the bones with the thickest walls and accept the reality that both the roundness of the shape and the thickness generally changes from one end of the 4"ish bones to the other. Buy a couple since you really don't know if the bone has the proper dimensions for the length you need until you cut it apart. Cost was $3.00 each.
Prepping the bone: To make the required rings, I elected to bandsaw disks off the length so I could use a glue block on the lathe to begin the shaping. The bone cut easily using my standard 3-tooth blade - I tried a finer 6 or 10 tooth but the gullets seemed to fill with the bone powder. The smell is pretty easily ID'd if you have ever had a tooth drilled - smells just like it to me. Sawing it is a dusty process but goes easily.
Gluing: The bone glued easily and securely to both the glue block and into the candlestick using CA and epoxy, respectively.
Lathe Turning: I found that shaping proceeded more smoothly with a scraping action rather than cutting. This could be a matter of the size and shape I was turning since I didn't have a more spindle orientation to really try a gouge. It is a dusty process and the dust will collect onto and into the chuck recesses. A dusting with a brush or air is needed once you complete the turning. I believe the bone has a more abrasive action on the tool edge than a dense wood, like African Blackwood or other tropicals, does. Perhaps it's just a matter of hardness or it might be an factor of the calcium or whatever. Frequent touchups of the edge is required or the bone won't respond to shaping very kindly. It seemed to me that the speeds that yielded the best shaping results were on the lower end of the spectrum - in the 500-1200 rpm range. Given that my lathe's lowest speed is 500 rpm I can't speak to speeds slower than that.
Sanding: Bone sands easily and beautifully - this is where bone's appeal as a component in a turning will become evident. I started with 220, then 320 and worked up to 4000 using Mirka's Abralon from 500 and up. Once you get to the 1000 and higher you will see the polish develop and the surface begins to look like ivory. Just beautiful.
Finishes: The finish I used was Behlen's Rockhard varnish applied to the entire turning once it was assembled. The bone seemed to accept it just fine and didn't change in appearance much, if any. Though I didn't use any other finish, I don't see why the bone would be affected negatively by whatever you use. As to leaving it unfinished, it appears to dull just a little over time. If it's a piece that's frequently handled I believe the white will soften to an ivory color. (I have an old bone burnisher/letter creaser (whatever it's called) on my desk that came from my grandparent's desk - it has a beautiful, smooth, light-ivory colored surface.)
For more info and visuals on bone and other non-wood materials for turning, look into Bonnie Klein's "Turning Unusual Materials" video.