Lloyd E. Sponenburgh wrote:
"Randy" wrote in message
...
I have an 11 inch diameter 1/4" thick 304 ss disk, no matter what I
try I get chatter, anyone do this? I need both sides flat and
parallel. 4" hole in center. no combination of feeds and speeds got
rid of the chatter. it has some holes through it and they seem to set
up chatter. I was chucked on the OD.

Embed the disk in a thin 'tray' of fixturing metal. It should help damp
vibration.

Or... adhesive laminate a sheet of lead to the backside before chucking.

Toolpost grinder.
SFM at the center is going to be much lower than the outside. Hard to
setup a single point cutter for that kind of range.