I am turning a bowl (about 6" in diameter by about 6" deep, side grain) from
green Black Walnut. I have shaped the exterior of the bowl. When I started
to power sand, I noticed that the outside of the bowl had several concentric
ripples. These ripples are a bit too deep to remove by power sanding, but
have eluded removal with a bowl gouge or scraper. I have not hollowed the
bowl yet, so it shouldn't be moving too much.

I have tried taking a very fine cut with a sharp bowl gouge, but the new
surface had just as many ripples. What is going on here? I'm pretty new to
green wood turning. Do I just need to rough the bowl and let it dry for a
couple of weeks before I proceed? Any suggestions will be much appreciated.
Thanks.

Barry
BRBR

Barry,
It sounds to me like you may be getting a harmonic vibration from the wood,
causing the ripples. Try varying the speed up or down and see if it helps.
Harmonic vibration results from imbalance and just the right speed. If you slow
it down or speed it up so the harmonic goes away it may do the trick.
-Jim Gott-
San Jose, CA