Monthly Archives: May 2015

Frame Handled Knives

I’m currently working on a new dagger project, as I had very good results with the last one. For this one I really wanted to use some ironwood scales, but I only have some thick enough for full tang (where the wood sandwiches the tang rather than the tang is inserted into it, which would be a stick tang). So for this project I’m trying for the first time a frame handled construction.

A frame handle construction is where you have a blade with a stick tang. Around this stick tang is assembled a metal case, in my case, copper, essentially transforming it into a full tang. On top and bottom of this, the tang is sandwiched with wood. This way you have the appearance of a full tang, yet before assembling the blade you can slide on a crossguard, which you cannot do with a normal full tang knife (due to the pommel normally being wider in diameter than the shoulder for the guard).

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Cocobolo and Maple Field Knife

The bolster of the original handle broke soon after assembly, and I wasn’t happy with the repair job I did, so I destroyed the old handle and replaced it, this time in cocobolo with a curly maple bolster, using the ricasso for a finger choil. The blade was forged from 5160, with forge scale left on. I’m considering removing it but leaving the texture.

Lucky

This was a project in trade for a friend, for a variety of woods and some leaf spring steel. T’was also her birthday very soon so I spent some extra time on it, something I need to focus on doing more with /all/ my knives, not just this sort.

So-called “Lucky” because I had several instances in which things had about a 50-50 chance of going horribly wrong, but in each case they worked up perfectly. When I was fitting the tang to the wood, I drilled all the way through it thinking the tang would be that long. In fact, because of the thick guard, It was shy of the edge of the pommel by about half a centimeter. I would need about half a centimeter further if I wanted to peen it over. This left me with a gaping hole in the pommel. The way I fixed this was by inlaying some turquoise into the pommel, very carefully carving out a depression around the hole with a dremel, and using epoxy and the end of the tang to support the stone. It worked perfectly. A bigger problem that scared me far more was when I was fitting the pin. The drill bit was too aggressive, and chipped the wood around the pin’s hole. The chip was too deep to grind down to. I nearly had to throw it away and restart right then, but managed to find the tiny splinter that had been thrown off by the drill. With a bit of epoxy it fit perfectly back into place, without a trace where the seam was.

The last bit of luck was with the heat treat. This blade is very thick, and so retains heat very long. When I quenched it in oil, only the steel near the tip hardened, and not the inside of the curve. I tried the quench again, with the same result. I tried it once more at a different angle and again it failed. My guess as to what was happening is the tip of the blade cooled and transferred the heat to the oil, heating the oil too much to harden the next section of steel. Whatever happened, I needed a more aggressive quench. I decided on the risky proposition of warm water. Water usually cools the steel too fast, putting a lot of stress of the steel and one time out of two will fracture it. If it cracked, I would have to throw it away and start the blade again. It went perfectly, quenched the edge, counted to three, took out of the water, waited a second, and repeated. Once the spine had lost color I cooled it fully. I took this photo just after quenching. The lighter area is hardened steel.

A perfect quench line. The darker area remains soft, while the lighter is very hard

All in all this knife was very fun to work with. The steel was forged from a rasp which belonged to the customer’s dad, which he had originally got when he was a kid. The guard is wrought iron, a type of pre-bessemer iron which is characterized by many slag inclusions, which show up with a light etch in acid. I used a brass spacer, brass and steel mosaic pin, rosewood from the customer, and turquoise inlay in the pommel.

The Southern Gentleman

This blade I forged several months ago but hadn’t got around to finishing, due to my being out of sharp drill bits. Recently I found out an efficient way to re sharpen them and so set about to finish it. The morning of the day I began work however, I went on an Art of Manliness article reading spree, which resulted in the unique finish of this knife. The style is called Brut de Forge, where many rough forged parts are left in instead of ground. This gives Brut de Forge blades and extremely tough and rustic look, which is enhanced when I combined it with the tough shape and thick, heavy steel, forged from a farriers rasp. The incredibly beautiful ironwood and brass pins balances this out, in a very smooth and refined finish. This combined tough and manly with comfortable, smooth and polite, all ideals that manifest themselves in the art of manliness, and especially the ideal of the “southern gentleman”, hence the name.

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Physics of Anvils

When looking for an anvil, we’re told a good trick to test if an anvil is good quality or not is the bounce test; let a hammer drop onto the face of the anvil using only it’s weight to push down and your hands just to stead the hammer. If it bounces only once or twice, it’s bad quality. If it bounces six or more times before coming to rest, it’s very good. But why is that? What makes an anvil good or bad and how does the above test reveal it?

Simply stated, a “bad” anvil will form the workpiece very little per given force in a hammer blow, whereas a “good” anvil affects the workpiece much more for the same force. So this is how it all works.

When you drop a hammer onto the anvil face, kinetic energy (whenever I use the term energy in this post, it will refer to kinetic energy) is transferred from the hammer to the anvil, and from the anvil deflected right back into the hammer. So why doesn’t the hammer bounce back up with the same speed it went down with? Why does it eventually stop bouncing? (remember nothing stops moving unless something, well, stops it from moving)

Let me explain elastic and inelastic collisions real quick. An example of an elastic collision are two hard steel balls, of equal mass and speed, hitting each other in a zero-gravity environment. Ball A is going five MPH to the right. Ball B is going five MPH to the left. They hit dead on. What happens? They bounce apart. Why? Ball A has transferred it’s kinetic energy to ball B, and vice versa, so after the collision ball A is going five MPH left, and ball B is going five MPH right.

An inelastic collision is where you have two balls of playdough in the same situation as above, striking each other dead on. What happens? They stick and flatten. What happened? Because the molecules were not rigid in relation to each other (the playdough is softer) the kinetic energy is used to expand the playdough outwards. Kinetic energy has to go somewhere, and as it cannot go as it had in the direction it was going, it is used to expand the playdough outwards, not into the other ball. The steel balls would do the same, but the force is not great enough to move the molecules in relation to each other, so it is transferred to the other ball.

So, going back to dropping the hammer on the anvil. If the anvil face is soft, (inelastic) the energy from the hammer is transferred into the hammer face, and then outwards and downwards, pushing the molecules away, into a dent. If the anvil face is hard (elastic) the energy cannot be used to move the steel molecules apart from each other (bonds are too strong), so it goes right back up into the hammer, pushing it back. Because no material we have is perfectly elastic (which would mean the molecules do not move in relation to each other at all, no material we know of has this property) some is used to move the molecules in relation to each other, and the rest goes right back into the hammer. Each time the hammer bounces a little more is lost until there is no more energy to keep it moving. If both the hammer and the anvil are hard, the hammer will fly back up with the same speed it had going down, which is why as a blacksmith you must be careful not to miss the workpiece.

So finally we can get to how this all relates to forging. For ideal forging, we want as much energy as we can to go into the workpiece, into moving the molecules in relation to each other. If the workpiece is hard, most of the energy is transferred from hammer, to workpiece, to anvil, and back to hammer with minimal amounts going into the workpiece. The ideal workpiece is inelastic. How do we make it harder? By heating it up so the molecules move easier in relation to each other. With a good hammer and anvil, the energy is transferred from the hammer into the workpiece. About half of the energy goes into moving the workpiece molecules, flattening it, and from there it spreads out from molecule to molecules until the effect is invisible. The other half of the energy is transferred through the workpiece to the anvil. Maybe half, but more like a third of that energy goes into moving the anvil molecules (but because the workpiece has spread the energy over such a large surface on the anvil, the effect is barely noticeable), then the rest goes right back up into the workpiece. Half of /that/ energy deforms the workpiece some more, while the remainder goes back into the hammer, pushing it upwards with just enough force not to shoot into the smith’s face, but enough to raise it so the smith doesn’t need to do any work to lift the hammer. Then the process repeats.