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

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

"Jim Gott" skrev i melding
...

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.



I agree absolutely with the vibe-thing.

But: The wood being green, it is already drying as you work with it.
So, it will slightly move and warp as you work, and you will never
find the good finish.

If you manage to finish it anyway, you will see it warp out of shape
as it dries further.

Rough the bowl to half-inch thickness or slightly more, leave material
for holding, inside and out, let dry thoroughly, finish.


Bjarte

Immediately plunge it into LDD and let it soak for a half a day. Remove,
drip dry, wipe with shop towel, remount and start turning. That ought to
take care of any potential cracking or warping. I am just wondering if you
might not be having problems between softer grain wood and harder grain.
The softer comes out easier and can leave a ripple effect. This was
discussed quite a few posts ago. The considered opinion was that it wasn't
from harmonic vibrations, but from the variation in softness between the
grains.

Leif
"Barry N. Turner" wrote in message
...
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

Another thing you might do is rub in a little of your finish in the problem
area and it will change the cutting properties.