Some people think it’s never a good idea to split wood with a knife and baton (“Knives aren’t made for that purpose, and they’re bound to break” etc., they say). Other people seem to do all their splitting with a “bushcraft knife” with a 4-inch blade and have never had any problems. Whether you agree or disagree with the practice of splitting wood with a knife, one thing that can’t be denied is that it works. It may not be perfect or ideal in every case, and there is plenty of evidence and examples of blades breaking, bending and getting stuck in knotty logs, but often enough, knives can be used successfully to split wood.
I first used a knife to split wood about 3 – 4 years ago. I split a lot of wood like that for a while, but nowadays I tend to use an axe for bigger stuff and only split kindling with a knife. One thing that I never really thought about until recently was whether there is a right way or wrong way to baton a knife. I usually just put the knife on the piece of wood and started hammering. This often worked, but I did run into problems with knotty pieces of wood and was concerned by several accounts of knives (thick-bladed, strong knives) breaking while being batoned. I had also experienced minor loosening of a handle on a stick-tang knife back a few years ago. After getting a new big blade recently, I wanted to make sure I didn’t mess the thing up by using it incorrectly.
This led me to think about splitting in a more “scientific” way. When we split with an axe, we apply the power of the swing and mass of the head to a relatively short cutting edge backed up by a wedge-shaped head. This is a very effective combination for splitting wood parallel with the grain. When splitting with a knife, there is a major reduction in the power of the swing (one-handed, using a baton) and the thickness of the blade. Instead of a swift and powerful blow with an axe, a knife is placed horizontally on the end of a piece of wood and hammered progressively deeper until the wood splits. Seeing as how this puts a greater amount of stress on a knife, I thought I would try to figure out the “best” way to baton to reduce the stress on the blade and handle, reduce the amount of energy expended and maximize the efficiency of splitting. I mainly focused on larger, heavier knives which could possibly compete with axes and hatchets. My findings don’t apply as much to smaller knives due to their light weight and short blade length, which make the physics of batoning less relevant and which I personally wouldn’t want to subject to heavy batoning anyway.
I started by thinking about the differences between how the force is applied to the wood when splitting with an axe and a knife. With an axe, the force is applied directly to the center of the end of the piece of wood (in most cases). If the axe gets stuck, the wood can continue to be pounded against a chopping block, further driving the axe head through. The force of the split is always in the axe head, and therefore centered in the wood. When batoning with a knife, the force is only centered in the wood when first pounding the blade into the wood. Once the spine of the knife is level with the top of the wood, force can no longer be applied to the center of the piece of wood (unless you use some kind of wedge on the spine). When the knife spine is flush with the wood, you have to start striking a part of the blade that is outside the piece of wood. What you now have is a lever (the knife) on a fulcrum (the point of tightest contact in the wood). When you strike down on one side of the blade, the other side goes up. This is less efficient than striking directly over the center of the wood.
One solution to this is to push the handle down while striking the blade sticking out of the other side of the wood, but this has been repeatedly shown to weaken and break knives (especially non-sandwich tang knives) due to the stress that results near the handle. So pushing down on the handle is not a good idea.
Striking the blade on the same side as the handle would require the handle to be held upward as the blows are struck. I think this would probably have a similar effect as described above and put unnecessary strain on the handle. I will look into this further, though.
So how do you make the best use of the force being applied while minimizing the lever effect and putting less stress on the knife? My solution is to arrange the knife and the wood in a way that directs the splitting force as close as possible to the center of the wood. The way to do this is to position the knife on the wood so the amount of blade that will be left sticking out on the tip side is just enough to be solidly struck with the baton, and also to strike the blade as close to the piece of wood as possible on the tip side (in other words, striking as close to the fulcrum as possible). Here, the mass and longer lever on the handle side counterbalance the baton blows on the tip side (the balance point of the knife itself should ideally be outside the piece of wood, on the handle side). These opposing forces on both sides of the knife enable the power of the blow to be directed as close to the center of the wood as possible, making splitting more effective. This greatly reduces the lever action of batoning, because the much shorter side of the lever (the tip side of the blade) is the side being struck.
After testing this “theory” I found that it worked surprisingly well in practice in both green and seasoned wood (I tested wood up to about 8 cm/3 inches thick with a 23 cm/9 inch blade), with and without knots. While I was testing, I did see a small amount of the lever effect, with the handle side starting to rise up, but it was only minor, and I just pushed the handle back down between baton blows (I kept my hand loosely on the handle just to keep the whole thing steady, but did not push down on the handle while batoning). I should mention that I started striking the spine of the knife directly over the center of the wood to get the split started and maximize the force. The results of my limited testing are very promising, and I will go out and try some thicker pieces of wood next time.
I would be very interested to know what you think about this and if anyone else has thought this much about this topic. 🙂 If my ramblings don’t make a lot of sense, I can try to make a simple diagram to show what I mean.