Some Thoughts on Splinter Pull

Sometimes, splinters will be pulled out of the first log, or the stump, or both. While this may not be important if you are cutting merely for fiber (such as firewood), it can be disastrous if you are trying to produce a high-quality product like lumber or veneer.

[splintered stump] A tree is composed of fibers that run vertically through the tree. The short fibers overlap, so that one, single fiber does not go the length of the tree. If the hinge breaks, it is because the fibers have failed, and there would seem to be two ways that can happen:

blank space

The fiber can break in two.
The fiber can be pulled out away from its neighbors -- pulled out by its roots, if you will. (You'll note that in the accompanying photograph, that's what has happened -- not surprising, since the center of the tree is rotten and there's nothing for the fibers that are left to hold on to.)

[splinter pulled straight] What can be done to help the fiber break, rather than be pulled out?
Well, assuming that if we bend the fiber it's more apt to break than get pulled out, let's think about that.
If we make an undercut consisting of only one, single cut, then cut in from the back, leaving only one single fiber left, then the pull on the fiber is straight tension.

[splinter bent] On the other hand, if we make an undercut of 90^o, then the fiber will be bent -- hopefully convincing it that it should break off, rather than be pulled out. Certainly, we have another reason to make an open undercut.

[thick hinge] Another instance where there will be a large, straight pull on some fibers occurs when the tree starts to fall with the hinge too thick. The fibers in the back will have a straight pull on them. (On a thinner hinge, all the fibers will be bent more before the stresses build up so high.)

[XXXXXX] If this happens because the tree falls before we can cut the hinge thinner, then what we need to do is to hold the tree until we've cut the hinge the way we want it. This is a common condition with trees that lean heavily in the direction in which we wish to fell them. And the deeper you make the undercut, the more this will be a problem.

[leaning tree] What we can do is to not cut the back of the backcut until we're ready. Modern chain saws allow us to plunge cut -- cut in with the tip of the bar -- so that we can cut the backcut up to the hinge, making it as thin as we'd like. The tree can't yet fall because it's being held by the wood left on the back of the backcut. When you're ready, continue cutting from the hinge back out to the back of the tree. Since the last fibers to be cut will be on the outside, the stress on them will be minimum they can be under the circumstances (that is, they have the most leverage) and they will be less likely to pull out. Besides, any splinter pull on the outside of the log will be of minimal value, since that wood would be slabbed off anyway at the mill.

blank space BUT! Be careful about kickback!

sarna@sarna.org

Last modified: Sun Mar 18 19:18:06 EDT 2012

	A tree is composed of fibers that run vertically through the tree. The short fibers overlap, so that one, single fiber does not go the length of the tree. If the hinge breaks, it is because the fibers have failed, and there would seem to be two ways that can happen:
	The fiber can break in two. The fiber can be pulled out away from its neighbors -- pulled out by its roots, if you will. (You'll note that in the accompanying photograph, that's what has happened -- not surprising, since the center of the tree is rotten and there's nothing for the fibers that are left to hold on to.)
	What can be done to help the fiber break, rather than be pulled out? Well, assuming that if we bend the fiber it's more apt to break than get pulled out, let's think about that. If we make an undercut consisting of only one, single cut, then cut in from the back, leaving only one single fiber left, then the pull on the fiber is straight tension.
	On the other hand, if we make an undercut of 90^o, then the fiber will be bent -- hopefully convincing it that it should break off, rather than be pulled out. Certainly, we have another reason to make an open undercut.
	Another instance where there will be a large, straight pull on some fibers occurs when the tree starts to fall with the hinge too thick. The fibers in the back will have a straight pull on them. (On a thinner hinge, all the fibers will be bent more before the stresses build up so high.)
	If this happens because the tree falls before we can cut the hinge thinner, then what we need to do is to hold the tree until we've cut the hinge the way we want it. This is a common condition with trees that lean heavily in the direction in which we wish to fell them. And the deeper you make the undercut, the more this will be a problem.
	What we can do is to not cut the back of the backcut until we're ready. Modern chain saws allow us to plunge cut -- cut in with the tip of the bar -- so that we can cut the backcut up to the hinge, making it as thin as we'd like. The tree can't yet fall because it's being held by the wood left on the back of the backcut. When you're ready, continue cutting from the hinge back out to the back of the tree. Since the last fibers to be cut will be on the outside, the stress on them will be minimum they can be under the circumstances (that is, they have the most leverage) and they will be less likely to pull out. Besides, any splinter pull on the outside of the log will be of minimal value, since that wood would be slabbed off anyway at the mill.
	BUT! Be careful about kickback!