Cutting tests

One thing I've always done, with every blade I've made, is test it. Both for cutting ability, edge-holding and toughness. Reason is, most of the blades I make have been tools, not wallhangers. Something like the dagger, I know, isn't likely to be actually used much, but it might. And it might be at a critical time. The other stuff, even the somewhat fancy, I expect will be used, sometimes a lot. And one thing that could keep me up at night would be the thought of someone really needing a knife I made to work and hold up to stress, and failing. It's not bridge engineering, but it's still not to be tolerated.

So I worked up a routine, varying a bit for different blade types. First step is to look the blade over very closely after heat-treating. Then sharpen it*. The most basic test is toughness, for which I take the blade, clamp the tip in a vise(how much in the vise depends on length/thickness) and flex it back & forth. It should flex and return to straight, repeatedly(amount of flex depending on the blade).

Second is the edge hardness with the brass rod, posted before.

Third is cutting. For edge-holding, I use 1/4" sisal or manilla rope, depending on which I've got or can find. I clamp a piece of 1x3 or 2x4 lumber in the vise. Then I use a marker to mark an area about an inch long. Then lay the rope on the wood, set the blade on it a little back from the end and push it down to cut through, then move the blade back a touch and repeat, over and over. A blade made of O1 or 5160 or harrow tooth, any good high-carbon steel, should make at least fifty cuts, and that area still be sharp enough to shave hair off your arm, and at seventy-five cleanly slice a piece of typing paper**.

That's for all knives. For a big one that might well be used for heavy cutting(firewood, etc.), I save branches pruned from the trees to test with, limb thickness depending on blade size, I usually use 2-3" for this(a lot of makers use 2x4). Set the branch on a solid surface(bigger branch) and chop it in two, then repeat. It's got to do this at least twice with no damage to the edge or bending of the blade, and still be at least usably sharp. The typing paper is good for this; you hold it by a corner, start near your grip and slice. If it won't cut it, or snags the paper where the blade's been cutting, problem: if it just won't cut it dulled too much, if it snags the edge roughened or nicked. If the latter, check the wood. I've seen a knot in some types of wood hard enough to mess with a knife edge, and if it's an old limb or used 2x4 there might have been a nail or staple in it.

That's the general process I use. It is subject to adjustment depending on the individual knife(I wouldn't expect one forged from a railroad spike to hold an edge like harrow tooth, for instance, but it'll be hell for tough).


*Remember, if the final grinding and polishing did not move the edge back any, you may well have an edge with a little bit of carbon loss from the heat-treating. I've read a couple of makers who say they don't expect a knife to show it's best edge-holding until it's been sharpened at least twice to make sure that decarburized layer is removed. And most bladesmiths leave the final-forged blade just a bit oversize, so the final grinding removes that layer.

**This is subject to the type of steel AND the use expected. Make a blade a little too hard and, while it may well pass the tests just fine it'll be a bitch to sharpen when it dulls; pain for the owner. Something of a lower carbon content- generally speaking- won't hold an edge as well, but can be made incredibly tough and will be easier to sharpen. Everything is a balance.