Knowledge You Can Build On — Est. 1998
reaction wood
DWFII
>In saw something in one of the threads that made me wonder if there was a problem with reaction wood...I mean as a general rule?
I've cut more than a few blanks out of what is probaly reaction wood...from limbs...and since I occasionally have problems with cracking (especially with my black locust stash) during or just after roughing out a bowl and I wonder if that could be the cause?
DW
In the High Desert of Central Oregon
Re: reaction wood
Carole in VA
>Certainly could be. There is a lot of pent-up stress in some limb wood. But then turners will turn just about anything we can get our gouges on, so keep spinning it. It's good practice.
Re: reaction wood
John K Jordan
>From Turning Green Wood: "Reaction wood is different in structure...and has different properties. Shrinkage, particularly in the longitudinal direction, can be 20 times greater than in normal wood... one of the reasons the timber industry avoids limb wood. But...turners can use timber with reaction wood effectively."
I would just be aware of the shrinkage factor, and keep an eye out for ring shake and cracks.
JKJ in East TN
cut orientation?
DWFII
>John, Carole,
Thanks to both of you. One follow-up...?
Does it make any difference how the blank is cut within the log?
I mean, some bowls might be cut opening towards the bark--pith at the bottom. Some might be cut opening towards the pith. And I could visualize a bowl cut so that the pith was at one edge of the bowl only (is that the same as "quarter-sawn?").
How will that affect shrinkage? Or turning?
DW
In the High Desert of Central Oregon
Re: cut orientation?
Carole in VA
>I try to cut the pith completely out, either when chainsawing the blank or immediately thereafter by rough turning. Get Bill Grumbine's video. He talks about how to cut blanks and seeing is worth a thousand words. You might also get that book "Turning Green Wood". I think the idea is not to have compression wood on one portion of the bowl and tension on the other...look for balance.
Re: cut orientation?
John K Jordan
>DW,
You might try to find a copy of the Turning Green Wood book. The author discusses (with great illustrations) most of the ways you can possibly cut a bowl from a log, burl, or crotch.
He has illustrations to help you visualize what the grain will look like after you hollow the inside, as well as a good discussion on drying and shrinkage in a chapter called "Shrinkage, stress, and distortion of bowls" along with illustrations of how the shrinkage is likely to occur based on the orientation of the blank in the log. I don't think he specifically illustrates shrinkage from reaction wood, but it could be inferred from the earlier observation.
JKJ in East TN
Re: reaction wood
Joe Herrmann
>About the only thing you will notice about cutting the wood with the bark out or the bark in will be in the orientation of the grain pattern. One orientation will produce a concentric cirle pattern on the inside of the bowl (bark out) while the other will produce the winged pattern.
Joe
