Barry:

I'd start by changing the speed a little bit and see if that helps. You
can run into speeds at which the blank resonates.

I think that a 1/4" bowl gouge is an almost useless tool. There just
isn't enough metal there to resist flexing even with a minimum overhang.
On the other hand, you might have tried a 1/2" gouge -- it may or may
not help.

I'd also look for defects in the blank. If there is a problem with ring
shake it often will show up as vibration and you would like to get it to
the firewood pile before it comes apart at 500 rpm.

Also, since I happen to know what lathe you are turning on -- make sure
that all 4 legs are sitting on the floor.

Bill

Barry N. Turner wrote:
I was hollowing a Sassafras bowl about 11" in diameter this afternoon. The
walls were about 1 1/4" thick and I was using my Crown PM 5/8" bowl gouge
with Ellsworth grind. Near the rim of the bowl, at the beginning of the
cut, I began to experience some vibration.

I put a fresh edge on the gouge and finished with little problem, but still
with some vibration. Then a thought entered my mind........had I switched
to a smaller gouge, say a 1/4" bowl gouge, which would remove less wood per
cut, would it lessen the amount of vibration? Thanks.