I don't know! Am looking for the same advice.
Presently thinking of checking a hardware store for
some kind of super strong sandpaper or a diamond
grinding wheel. I wouldn't use the wheel on a drill, but
use it manually to smooth out the chips.
The other thought is to take it to a glass blower.
It might be possible to heat the chip of the goblet
so that it melts. Wouldn't try this myself as
believe the goblet would crack if not done right.
R Richard Layman, September 2004