JR Johnson wrote:
Guys, I am building a coring lathe to cut bowl cores from half a log
section. That's right, I am primarily a wood turner, but I built both my
lathes from scratch, so I am somewhat metal capable.

The coring lathe will take a log half section and secure it with a
faceplate. Then the largest coring cutter that will fit the log half will
pivot into the faceplate side of the log and cut the corners, etc. away,
leaving the outside of the largest bowl. Then the next coring cutter will
pivot into the log half and remove the largest bowl. And so on down to the
smallest bowl.

To support the cutters, I need perfect (essentially, plus/minus 0.0625 would
be ok) spherical sections. In a perfect world, the largest section would
have a 12" inside radius, the next a 10.5" radius, the next a 9.0" radius,
then an 7.5", 6.0", 4.5" and finally an 3.25" radius. Wall thickness
needs to be 0.250".

What's wrong with simply using a bar bent into a circle?
Remove some metal at the appropriate edges to thin it while retaining
the stiffness.

First drill/cut out a 2" or so conical plug inside the 3.25" bowl.
Now, place a couple of bearings on a really, really thick bit of metal
supporting a sickle-shaped cutter in the hole.
The sickle shaped bar with cutter on the end is then advanced into the
work to cut a hemisphere.