Heat Treating part VII

Summary and Miscellanous
 

This is the last of the articles series on basic heat treating. I'll be putting them all together in a PDF for E-book form shortly, and I'll keep you updated on the progress of this. With the close of this series, I'll be starting a new one next week, and haven't yet settled on a subject. If there's anything you're curious about and would like to have addressed, shoot me an email!

Today we're running through a basic summary of the past six articles. 

The first element to understanding heat treating is that of hardness, and toughness. A hard knife will stay sharp (hold an edge) but is brittle, a tough knife will not break but will easily dull. The harder a knife is, the less tough it will be. The tougher a knife is, the less hard it will be. The point of heat treating is to get at just the right point between the two extremes. Coincidentally, this is often yielding in a springy steel, one that will not take a set when bent. 

Now the second element in understanding heat treating is at the molecular level. 
Iron is an element, carbon is also an element. Steel is an alloy; a mix of the two, and often other elements. Steel requires a certain amount of carbon in order to be properly heat treated, generally between .40% and 1% Carbon by weight. This is known as high carbon steel. 

High carbon steel, at room temperature, is generally in a small, tight cubic formation called Body Centered Cubic (BCC). When heated past critical temperature, which can be tested by using a magnet (it loses magnetic attraction at this point), the atoms switch formation into face centered cubic (FCC) which is also a cube formation but slightly larger and more open. Carbon atoms, which interspersed between BCC cubes, now move inside the FCC cubes.

If cooled extremely slowly over many hours, the FCC slowly changes back to BCC and the carbon atoms slip out into nice, easy locations, and the entire piece of steel moves to the easiest, most "relaxed" state. This is known as annealing, getting the steel dead soft.

If cooled at a normal pace (air cooled), much the same happens but the steel retains some hardness. Doing this several times (heating then cooling to black), each time will refine the grain structure of the steel. 

If cooled at a very rapid pace, using a quenchant liquid such as oil or water, the carbon does not slip out in time. The structure becomes very rigid, tough to move in relation to one another but when they do it's at the breaking point. 

Normalizing is done, as mentioned above, by heating a bit above critical and allowing to cool until it's completely lost its color. Why? Steel is made up of "grains"; granules of atoms that are all linked together in a cubic formation oriented the same way. A bordering grain will have its atomic orientation a slightly different way. This border is a weak point. The larger the grains, the weaker the steel. You can see the grain structure in the broken surface of steel, ranging from milky looking to coarse sand. 

Normalizing then, is to refine; that is, multiply and shrink these grains. The more a steel is kept at a malleable temperature and forged, the larger these grains grow. Now, when the steel is heated past critical, FCC grains begin to form at the borders of BCC grains. Once it's been completely converted to FCC, the steel is left to cool and now BCC grains form at the border of the FCC ones. This is repeated several times, each time because there is little time to keep growing, the grains get smaller and smaller. 

Hardening is done by heating to critical and cooling very rapidly, using a quenching like water or oil. The rapid cooling entraps carbon atoms inside cubes too small for them, and a lot of rigidy is put over the structure of steel. The atoms are hard to move in relation to each other (thus it will not dent or bend) but when they do, it's by breaking. 

Tempering is done by heating anywhere in between 350 F to 450 F or so for an extended period of time; this eases up on the steel's pressure, toughening it and making it less brittle. 

Warps

Often during a quench, the steel becomes warped due to uneven cooling or stirring in the quenchant. It is unwise to try to straighten it directly after a quench, or even putting pressure after tempering. I've found that by far the most effective and least risky way is to make a jig to bend it slightly in the opposite direction of the warp, and temper like this. The heating makes it slightly more plastic and more likely to take a set, and it is far more controlled then trying to bend it after tempering. 

Differential Heat Treating

As mentioned above, a good blade is one that can hold an edge and that is tough enough to withstand shock in use. One way to get the best of both worlds is to leave a spine that is soft and tough, and so can take much stress, and an edge that remains hard, although brittle, so it can keep an edge. 

This can be done in one of two stages. During tempering, and during the quench. 

If done during tempering, the process is simple. Using something like a torch, the smith heats up the spine only, to a bluish temper color, avoiding heating the edge as much as possible. 

If done during hardening, we can again break it down into two methods, both based on a simple principle which is this: if the steel is heated to critical temperature, and cooled within a certain time frame (i.e., if the steel cools within 3 seconds, it hardens, if it takes 4 or more, it remains soft), it will harden. 

Based off that principle, the first method is by heating the edge only to critical, then quenching. Thus, only the edge hardens. 

The second, you can simply heat up the entire blade but only quench the edge in the quenching liquid. This means the edge cools within the required timeframe but the spine does not. Similarly, a method was developed by the Japanese called Yaki Ire- the clay quench. An insulating clay is applied over the blade's spine, and the blade is heated and quenched in full. The clay slows the cooling rate of the steel underneath it, and so that steel cools too slowly to harden. The benefit of a clay quench is that when polished and/or etched, the steel exhibits a border line between the soft and hard steels, which is often breathtakingly beautiful. 

This covers and summarizes all the articles so far. I apologize for today's article being rather late, but I'm glad it's finally out. Once again, suggestions for future articles are welcomed, shoot me an email, or if you have any questions I would be glad to help out!

Caleb Harris

I’ve always fooled around with tools and hardware, but I think my passion with blades started far back in my childhood: wooden swordfights with the neighborhood kids. I became the neighborhood “blacksmith”, using my grandfather’s tools to hammer little crossguards onto wooden sticks. I always tried to find the best scrap wood: lightest, strongest, trying to get the perfect length and shape for each “customer”. This started my passion with blades.
 
When I was ten years old, I joined a local rock and gem club, learning stonecutting and cabbing, and through that came to take silversmithing lessons from a local jeweler. It wasn’t until around the age of 13, that I turned my attention to bladesmithing, which has captured my heart. 
 My personal obsession with bladesmithing, as I’m sure you can relate, isn’t just the joy and passion of the making: the musical clang of the hammer on steel, the shower of sparks on the grinder, the whisk of the blade over the sharpening stone, but also of the fulfillment in creating something that is twofold: that of beauty, and that of function. It’s trying to make something that is as much an art piece, as a tool that you can trust your life with. That’s what caught my heart, and the pursuit of that perfect combination still drives me.  

An Intro to Heat Treating, Part VI

Differential Heat Treating

As mentioned way back in the first article of this series, there are two basic qualities of steel. Hardness/Brittleness, Toughness/Softness. A harder steel will be less tough, and a tough steel will be less hard (capable of holding an edge). 

But what if you could get the best of both worlds? This is the thinking behind differential heat treatment.

If the edge is harder than the spine, this should increase performance a good deal.

However, a disclaimer is required. Tempering is still very much necessary even with a very tough spine. Most fully hardened steels are too brittle to hold up as an edge; no, they will not bend and dull, but it can chip. Tempering (though possibly at a lower temperature than normal) is still required. 

 There are two main ways to do a differential heat treat. One is in hardening, the other in tempering. 

Tempering is fairly simple, and I touched on this in last week's article. Differential tempering is done by heating the spine, while leaving the edge cool. Usually this is done with a torch, carefully heating the spine to a nice blue color or so (around 600 Fahrenheit). It's risky to do this in air however, as the heat can very easily creep down towards the cutting edge, ruining the temper. 

The other way is by differential hardening. There are several ways to do this. Now, the basic principle is this: if a steel must be cooled from a certain temperature in a certain timeframe, it will be hardened. To keep a portion of steel from hardening, you simply need to either slow down the cooling, or not get the steel hot enough. 

So, firstly, we can heat only the edge to critical temperature. This can be done with something like an oxyacetylene torch; heat up the edge, test with a magnet, heat some more, and quench. 

A second method would be to do an edge quench. This is done by heating the entire blade, and only holding the edge of the steel in the quenchant. With experience, this can be done with great results, but beware too much heat creeping down from the spine. 

A third method would be to quench the entire blade, keeping in mind cooling rates, temperature, and mass of the blade, and remove the blade quickly enough. With enough mass on the spine, and little enough thickness on the edge, it is possible to use timing and calculation to produce an "autohamon"; where the edge is hardened and the spine remains soft.


The fourth and most famous method is to use an insulating clay in a "clay quench". This method, used in traditional Japanese bladesmithing, is to coat the spine in an insulating clay, heat up the blade, and quench. The edge hardens normally while the clay slows the cooling of the spine. This leaves the spine soft while the edge is hard. With careful controlling of temperature and especially the clay, absolutely insane hamons can be produced.



Hamon 刃文

When a blade is differentially hardened, there will be a section of soft steel and a section of hardened steel. If the steel is properly polished and/or etched, the border between the hard and soft steel while become visible as a line of varying appearance. This visible line is called a "hamon", and is highly prized. It can appear either as a dark line separating a gray section from a silver, or it itself can be a ghostly white flame flitting through the steel. Collectors of Japanese swords deal quite extensively in the shapes and characteristics of hamons.


Bringing out a hamon again is based on a fairly simple principle: one area of the steel is hard, another is soft.
There are two standard ways then, to bring out a hamon. The first is the traditional Japanese method: polishing. Learning to do this perfectly takes years and many expensive natural abrasive stones, but it can be replicated by hand to a lesser extent. Exact methods are beyond the scope of this article. However, the idea is using various abrasive stones to rub away at the surface of the steel: the softer steel will wear off at a faster rate than the harder, and proper application can bring out some very stark contrast. 

The second method is by acid etching: acid eats away at the softer steel at a different rate than the harder, and a different rate at the border line itself (hamon). The ideal acid is diluted ferric chloride (circuit board etchant), but boiling vinegar or even lemon juice will work. Everyone has slightly different steps in etching; a black oxide layer forms on the surface, and it must be cleaned of periodically throughout the etching process. The surface finish pre-etching, longer etching, more or less frequent cleaning, acid concentration, and cleaning type will all have some effect on the appearance of the hamon. 

Deep-hardening and Shallow-hardening steels

In the world of differential hardening, there's an important factor to keep in mind: steel. Basic carbon and tool steels can be divided (so much dividing in this article!) into shallow and deep hardening steels. The difference is based on required cooling rates. 

For example, we take a made-up steel, Steel D (D for Deep hardening), in order to harden, must cool from 1600 F to 400 F in five seconds. If it takes six seconds to cool this far, the steel will not harden. However, five seconds is quite a long time. A plain blade in oil can cool this entire rate in three seconds. So if we apply clay, which slows the cooling of the spine by one second, we still have a blade completely cooled in four seconds. Thus, the clay has no effect. The blade has hardened through and through. 

Steel S, (for Shallow hardening) takes three seconds at the same temperatures to cool. If we retard the cooling by one second using clay, the surface underneath the clay takes four seconds, exceeding the upper limit required for hardening. And so, this area remains soft. A thicker chunk of shallow hardening steel, even if quenched without clay, may differentially harden due to the extra mass and residual heat, or the surface may even harden while the core remains soft. This last point is what is referred to when we say deep or shallow hardening.

Whether a steel is deep or shallow hardening depends on its chemical content. As a general rule, the more complicated the makeup, the deeper hardening the steel is. Some elements may extend or shorten the time required to harden. This is why one steel, such as W2, more readily takes a hamon, while another, such as 1084, is a little tougher to selectively harden. 


So there you have it, the basics of differentially heat treating. This process can be broken down into two main branches: differential tempering, done usually by heating the spine post hardening, and differential hardening. Differential hardening in turn can be broken down into either selectively heated edge quenchingmono-temperature edge quenching, creating an "autohamon", and clay quenching
The Hamon is the visual effect of a differentially hardened blade, brought out either by polishing, acid etching, or a combination of the two. 
The type of steel will affect whether it is possible to selectively harden a blade, given the same processes. Some steels are shallow hardening, requiring a short window of time to harden, and some are deep hardening, allowing for a longer window of cooling rate to harden.

This is the sixth and second to final article on basic heat treating; next week I'll do a basic run-through of the subjects we've covered as well as some anomalies that didn't fit into the subject titles we've named so far. 

Caleb Harris

I’ve always fooled around with tools and hardware, but I think my passion with blades started far back in my childhood: wooden swordfights with the neighborhood kids. I became the neighborhood “blacksmith”, using my grandfather’s tools to hammer little crossguards onto wooden sticks. I always tried to find the best scrap wood: lightest, strongest, trying to get the perfect length and shape for each “customer”. This started my passion with blades.
 
When I was ten years old, I joined a local rock and gem club, learning stonecutting and cabbing, and through that came to take silversmithing lessons from a local jeweler. It wasn’t until around the age of 13, that I turned my attention to bladesmithing, which has captured my heart. 
 My personal obsession with bladesmithing, as I’m sure you can relate, isn’t just the joy and passion of the making: the musical clang of the hammer on steel, the shower of sparks on the grinder, the whisk of the blade over the sharpening stone, but also of the fulfillment in creating something that is twofold: that of beauty, and that of function. It’s trying to make something that is as much an art piece, as a tool that you can trust your life with. That’s what caught my heart, and the pursuit of that perfect combination still drives me.  

An Intro to Heat Treating, part V

Tempering The Blade

The first thing to remember is the principle I brought up in the very first article of this series:

Steel can be thought of on a sliding scale of Toughness/Softness to Hardness/Brittleness. 

If hardening jumps us to the extreme hard and brittle end of the spectrum, tempering is the process to bring it back down to the ratio we want. That said, tempering is really a very simple process. 

The basic idea is to thoroughly heat the blade at a fairly low temperature, ranging from 350 F - 450 F. The hotter the temperature, the softer the steel. Many folks use a kitchen oven (use a thermometer; the built in one is usually fairly inaccurate), but a toaster oven is plenty ideal.

Now many people use a method called "torch tempering", which technically works okay, but it's inconsistent and risky. Torch tempering is using a torch to heat only the spine of the blade anywhere from a straw yellow to a blue color (called "temper colors"), thus toughening the spine and leaving the edge hard. However the problem with this is that it's incredibly easy to heat the cutting edge, softening it too much and thus ruining it. This would result in having to re-harden the entire thing. The other issue is that the steel isn't completely "soaked" in the heat for a sufficient time, and it can still remain very brittle. 

So, the ideal way to temper is for several hours. Various makers will temper anywhere from 3 to 6 hours, ensuring a thorough heating. A common method is to temper in several cycles: for instance a few hours at 420 F, cool in water, then a few hours at 375 F. 

Now remember, the temperature you use depends on the steel. This can be found by googling different heat treating charts for the steel type. 1095 steel tempered to 400 F will not act the same as 1084 steel tempered to the same temperature.
Not just this, but a sword will require a higher temperature than a paring knife, for example. A sword needs to be much tougher than a paring knife does. 

So, that gives you quite sufficient to perform your own heat treats. The key to getting excellent results (chopping boards of wood while retaining the edge, bending without snapping, etc.) is constant testing, noting, modifying, and retesting.

Walter Sorrels has an excellent video on testing, I highly recommend checking it out. 

Now, as tempering is indeed fairly simple, I'll move on to the subject of warps, and more specifically, removing them. 


Warps and Straightening

Especially with longer blades, it's very easy to get a warp during the quench. This is usually due to uneven cooling in the quench, mostly something like stirring side to side rather than in a cutting motion. In any case, a warp is always possible, even when you think you've done everything to prevent one. 

So, straightening the blade. There are several methods to doing this. A common one, is to flex the blade in the opposite direction of the warp directly out of the quench, while the blade is still steaming or smoking. It's generally able to take a change in direction before it's completely cool and set, but this is incredibly risky. One pound too much force and snap goes your blade. This can be done effectively, however it's best left to those with a lot of experience and have a deep intuition to know the breaking point. 

Another method is to try putting pressure on after tempering. Assuming you've tempered the steel soft enough to take a set rather than spring back in blade, you can set up a jig in a vise using a few pegs to straighten it. Two pegs on one jaw of the vise, on the inside of the warp's curve, and a third on the other jaw, on the outside and center of the warp's curve. When you tighten the vise, this will bend the blade in the opposite direction, hopefully enough to take just enough of a set to straighten it. 

However, if you didn't temper hot enough to take a set, one of two things will happen. First, you'll have to bend it very far to take a set. Second, it may snap before it gets quite that far. Tough though blades may be, they're not meant to be flexed that far. 

The two methods above are known as cold straightening. I've snapped many a blade trying these and it's not pretty, though it does enable you to see the grain structure to check your normalizing job. 

So, since then I've elected to take a much safer, and in my opinion, more effective, of an approach. 

Quite simple, really. I've found that if you straighten the blade while it's tempering, it's in a hot state, and changing, and is more susceptible to taking a set. My preferred method for doing this is get a flat bar of fairly thick steel and gently clamping the blade along it using a c-clamp (inside of the warp's curve against the steel). Sometimes if this still springs back I'll put two pegs between the blade and the bar, each peg at opposite ends of the warp. The C-clamp's pressure in the middle causes a reverse flex, and while not enough to take a set cold, it should do so nicely while tempering. Be careful not to over tighten before it's begun tempering; hardened steel is extremely brittle. I like to sometimes just get the blade "taught", then tighten at several intervals throughout the tempering cycle. 

This technique has produced the highest rate of successful straightening for me. Another method that I've found to be effective without risk of snapping is when cooling in between tempering cycles. When you cool with water between cycles, if you cool in a sink or something and spray the water on the outside of the warp's curve, that will cause that side to contract slightly faster than the opposite side. With experimentation, proper application, and a dash of luck, you can bring the blade back to perfectly straight using just water. This of course depends how serious the warp is. 


So, tempering is the process of heating hardened steel anywhere from 375-450 degrees fahrenheit. This softens and toughens the steel just the right amount, to bring the steel to the desired balance between toughness and hardness. Warps can occur during the quench, and I've found that straightening is best done during tempering, both for effectiveness and to lower the risk of snapping. 

With tempering, we've covered just about everything in basic heat treating. Next week, I'll delve a little bit into selective hardening and hamons. Note however that I'm not an expert on clay heat treating, but I've done my bit and will pass on what I've found most helpful. 

Caleb Harris

I’ve always fooled around with tools and hardware, but I think my passion with blades started far back in my childhood: wooden swordfights with the neighborhood kids. I became the neighborhood “blacksmith”, using my grandfather’s tools to hammer little crossguards onto wooden sticks. I always tried to find the best scrap wood: lightest, strongest, trying to get the perfect length and shape for each “customer”. This started my passion with blades.
 
When I was ten years old, I joined a local rock and gem club, learning stonecutting and cabbing, and through that came to take silversmithing lessons from a local jeweler. It wasn’t until around the age of 13, that I turned my attention to bladesmithing, which has captured my heart. 
 My personal obsession with bladesmithing, as I’m sure you can relate, isn’t just the joy and passion of the making: the musical clang of the hammer on steel, the shower of sparks on the grinder, the whisk of the blade over the sharpening stone, but also of the fulfillment in creating something that is twofold: that of beauty, and that of function. It’s trying to make something that is as much an art piece, as a tool that you can trust your life with. That’s what caught my heart, and the pursuit of that perfect combination still drives me.  

An Intro to Heat Treating, Part IV

Hardening

After several cycles of normalizing, and after the blade has been ground to rough shape, you still don't have what many knifemakers will call "a knife".

The more philosophical among our craft will call it a "knife shaped object" at this point. 

The quench is where the steel begins to become a proper and capable blade. 

So, let's get down to what happens

If you remember the very first article in this series, in blade terms there are two basic qualities that are on opposite ends of a sliding scale. The first is toughness/softness, and the second is hardness/brittleness. A very tough blade is rather soft and will not hold an edge, but a very hard (edge retaining) blade is rather brittle and will break easily. 

The final heat treating in simple terms is broken down into two basic parts. Hardening and Tempering. Hardening comprises of hardening the blade (who would thunk?) and Tempering softens it sightly, to the exact hard-tough ratio you like. Today we're talking about hardening. 

The smith begins by heating up the blade as evenly as possible in a furnace, kiln, or forge, to reach critical temperature. Professional smiths will use a very controlled heat treating kiln, to reach just the right temperatures and hold those temperatures (soak) for just the right amount of time. These times and temperatures of course vary from steel to steel, but for basic terms in the scope of this article we're just concerned with getting a nice even hardening. 

In something like forge with a single area of heat that might not reach the entire length of the blade, the best method is to slowly draw it back and forth to get an even heat over the entire length. If possible, keep the blade out of the direct flame, this helps to reduce warping, scale buildup, and uneven heat. A common technique is to use a scrap steel pipe as a "mini kiln", which is place under the flame. You can then draw the blade back and forth inside this pipe to get a near perfect, even heat. 

In the absence of a thermometer there's one way to test whether you've gotten up to critical temperature or not. Once the phase change happens (atomic structure goes from BCC to FCC), the steel loses it's magnetism. So, you can touch a magnet to the steel as a test: if the magnet sticks, it's not hot enough. Put the steel back in the forge and heat it up some more, then remove it and test again with the magnet. 

An excellent technique is to always heat treat at night or in relative darkness. That way, after you've heat treated a few blades using a magnet to test, your eye will grow accustomed to the glow and color of the hot steel, and you'll know exactly when you're at the right temperature without having to magnet test. If you heat treat at various times in various lighting, the steel will appear different each time. 

Now that the steel is up to temperature, the next step is the quench

The basic idea behind hardening is this. The steel, at roughly 1600 Fahrenheit, switches atomic structure. If you can cool the steel down to a certain temperature within a certain timeframe, the steel convert to a hard, almost glass-like state. Cooling in plain air is too slow for most steels (there are exceptions!), and so a liquid is the best bet for an even, fast quench. 

That said, let's have a word about different quenchants. Plain water is a common quenchant, traditionally used in Japanese bladesmithing, but it's often too violent of a quench. Both because it's extremely fast of a quench, and because the vapor bubbles create a very unstable environment for the now-glassy steel, and the shock often results in a sharp *PING* noise, indicating a fracture in the blade. 
Because of this, various oils are used. The standard professional oil, Parks 50, is of course ideal, but other oils such as motor (not healthy when burned, so be warned) oil, peanut oil, olive, canola, etc. work very well. Often using a brine helps eliminate the violent bubbles in a water quench. Preferably do some preheating (120 F or thereabouts being ideal) for the quenchant, this lowers the viscosity and makes for a more thorough quench. 

Now sometimes there can be issues with using just oils (too slow), as well as just water (too fast or too violent). This is where you can experiment with interrupted quenches, but that'll be a future article. 

The actual quench must be very quick and very precise. Have the quench tank nice and close to the forge but give yourself plenty of room. 

You can quench either horizontally (edge first) or vertically (tip first), but for our intents and purposes it doesn't really matter all that much. Quenching horizontally, if you can, gives you the ability to edge quench (again, more on that in future articles) and observe different factors that may lead to a failed heat treat. 

Completely submerge the blade in the liquid. For constant cooling, move it back and forth in a cutting motion: don't go side to side, as the blade is still in a plastic state and this can cause warping which is a nightmare to get rid of. 

If you quench in oil, there can be flame, but really you don't actually want this. Any portion of the steel hot enough to cause a flame should be completely submerged. To put it simply, fire needs three things. Oxygen, Fuel, Heat. If the hot steel is completely submerged, there's no oxygen immediately adjacent to the oil that's actually hot enough to catch fire. 

Continue to stir back and forth until the smoke is nearly gone, and the steel will be cool enough. I like to remove it, wipe off with a rag, file test, check for warps, examine for any cracks, then immediately go to tempering. 

The File Test

There are numerous factors that could lead to a failed quench. Whether too cold of steel or oil, uneven heating, too slow of transfer, even things such as atmosphere humidity can affect a quench. So, it's important to check whether the steel hardened up properly. 

The way to do this is with a file. Files are heat treated to a very high hardness; the teeth need to be extremely hard to stay sharp, but a file isn't put under much stress so it can be fairly brittle. Of course, they are still tempered (softened slightly), so a file is the perfect thing to test hardness. 
It's quite simple. 
If the blade hardened successfully, it will be harder than the file. If it failed, it will be softer than the file. So, if the file is harder than the blade, then when it's drawn across the blade's edge, it will cut in and drag. If the file is softer than the blade, then the file will simply skate over the surface as if it were glass. 

Examining for Cracks

Possibly the most heart dropping sound in bladesmithing is the tiny *ping* or *tink* that comes with a fracture forming in the quench. The fractures that come from this rarely form across the entire blade, rather being anywhere from a few millimeters to more than a centimeter in length, perpendicular to the blade,  and starting at the cutting edge. 

Unless you're making yourself a scrap blade, if you find a fracture, it's time to scrap it or see if there's enough steel left to chop it into a smaller blade. Never try selling a blade with a crack in it, even if it's practically invisible. 

Now the blade is usually covered all over with black oxides from the quench and it's often hard to see if what you're looking at is a crack, or something like a scratch filled with oxide. So long as you see a matching mark on the other side, indicating it went all the way through, then you can be sure it's a fracture. Scrap it.

So, you've heated, quenched, tested for hardness, and examined for cracks. The final step before tempering is to check for warping. It is very easy to do this. Hold the blade up so you're looking down the length of the spine, as if you were looking down a rifle or shotgun barrel. This enables you to see very clearly any wobble or warp. If the spine looks straight, flip it over and look down the cutting edge. If they check out, it's on to tempering.

If not, if you see a warp or wobble, then there's an extremely tense straightening process to do simultaneously to tempering. Most blades are ruined during the quench itself, but a close second is when you try to straighten and don't do it just right. 

I'll cover correct warps as well as tempering in next week's article. See you then!

Caleb Harris

I’ve always fooled around with tools and hardware, but I think my passion with blades started far back in my childhood: wooden swordfights with the neighborhood kids. I became the neighborhood “blacksmith”, using my grandfather’s tools to hammer little crossguards onto wooden sticks. I always tried to find the best scrap wood: lightest, strongest, trying to get the perfect length and shape for each “customer”. This started my passion with blades.
 
When I was ten years old, I joined a local rock and gem club, learning stonecutting and cabbing, and through that came to take silversmithing lessons from a local jeweler. It wasn’t until around the age of 13, that I turned my attention to bladesmithing, which has captured my heart. 
 My personal obsession with bladesmithing, as I’m sure you can relate, isn’t just the joy and passion of the making: the musical clang of the hammer on steel, the shower of sparks on the grinder, the whisk of the blade over the sharpening stone, but also of the fulfillment in creating something that is twofold: that of beauty, and that of function. It’s trying to make something that is as much an art piece, as a tool that you can trust your life with. That’s what caught my heart, and the pursuit of that perfect combination still drives me.  

An Intro to Heat Treating, part III

 

Note: As I'm writing this I realize that the amount of information I originally wished to contain in this article was far too much, therefore this week's article is focusing on Normalizing alone

Now that you understand what goes on in the chemical structure of steel, we can focus on applying this knowledge. 

First, a couple disclaimers:

You may do everything to the letter I've outlined in this article and in the past few, and you won't be chopping boards and shaving hair. This is because different steels require different temperatures, and for truly excellent heat treating, you must start out with the temperatures and processes outlined in steel charts for the steel you're using, then further test and tweak to get it where you want it. 

So, let's get to the actual process. Heat treating is a general term for using various heating and cooling rates to change the physical properties of steel. Underneath this we can break simple heat treating down into three basic processes: Normalizing, Hardening, and Tempering. Now there are a few others, such as Cryo Tempering and Annealing, but we won't get into them until the last few articles. 

Normalizing

After forging, steel has a lot of stresses and a large grain size, which makes the steel quite brittle without being hard. Normalizing is done in several cycles, two or three after forging and another cycle after rough grinding.

If you remember last week's article, a steel bar will be formed of many grains, which are composed of steel atoms arranged in a particular pattern (BCC) along a certain plane. One grain will have a pattern oriented in a slightly different angle than the grain next to it.

Larger (and so, fewer) grains produces a weaker structure than smaller (and so, more numerous) grains. The goal of Normalizing is to minimize the size of the grains. 

As the steel is heated past critical temperature, new grains (FCC structure) will begin to grow along the borders of the already formed BCC grains. Soon past critical temperature, all the BCC grains have been converted to smaller and more numerous FCC grains.

A side note: If this temperature is held, and further, if the steel is worked say by a hammer, some grains break down and join their larger neighbors, and the overall grain structure is made larger. This is obviously not what we want. 

The process for normalizing thus far is as follows: the steel is heated up to critical temperature, often a little hotter to make sure of full grain conversion. Once you're sure it's evenly heated, remove the steel from the heat and let it air cool until it's completely black. 

So what does that do? As the steel cools below critical temperature, the grains once again begin to convert; BCC grains form and the junctions of the FCC grains. Again, these grains are slightly smaller than the previous ones. 

Heating and cooling like this is one cycle of normalizing. This process is repeated, usually 2-4 times, each time further refining and shrinking the grain size. 

Many knife makers will occasionally make a test blade, and after various chopping and cutting tests, and finally testing it to destruction where the blade breaks, will observe the grain structure. The steel will not break through the grains, rather, the weak points are the junctions in the grains, so a broken end of a steel bar will show you quite clearly the grain size, as in the cover photo at the top of this article. 

So there it is, the process for normalizing. To recap, normalizing is done by heating a bit above critical temperature then letting it air cool until completely black. This cycle is done three or four times. Many smiths prefer two or three cycles after forging, and another cycle after rough grinding. The effect of normalizing is to refine the grain structure and relieve stress, creating a blade with much higher overall strength. 


P.S. As mentioned at the beginning of this article, I originally intended to stuff all the different parts of heat treating into one article,  but that was far too much information. So, next week, we'll take a look at hardening. Before hardening, you have a "knife-shaped object". If it survives hardening, a real blade is truly born. 

Caleb Harris

I’ve always fooled around with tools and hardware, but I think my passion with blades started far back in my childhood: wooden swordfights with the neighborhood kids. I became the neighborhood “blacksmith”, using my grandfather’s tools to hammer little crossguards onto wooden sticks. I always tried to find the best scrap wood: lightest, strongest, trying to get the perfect length and shape for each “customer”. This started my passion with blades.
 
When I was ten years old, I joined a local rock and gem club, learning stonecutting and cabbing, and through that came to take silversmithing lessons from a local jeweler. It wasn’t until around the age of 13, that I turned my attention to bladesmithing, which has captured my heart. 
 My personal obsession with bladesmithing, as I’m sure you can relate, isn’t just the joy and passion of the making: the musical clang of the hammer on steel, the shower of sparks on the grinder, the whisk of the blade over the sharpening stone, but also of the fulfillment in creating something that is twofold: that of beauty, and that of function. It’s trying to make something that is as much an art piece, as a tool that you can trust your life with. That’s what caught my heart, and the pursuit of that perfect combination still drives me.  

An Intro to Heat Treating, Pt II

 

Last week we ran through not what we do in heat treating, or how, but why. The why is always imperative. It's hard to go on a journey if you have no idea where you're going. 

For a quick refresher, there are two basic qualities of steel on opposite ends of a sliding scale. One the one side is hardness, which equates to brittleness. Think of it like glass. On the opposite end of the scale, is toughness, which equates to softness. Think of it like copper. A very hard knife will hold an edge but will break easily, a tough knife will keep strong and  intact but will dull easily. A good knife will be somewhere in between the two. 

We can put our blade in between those two qualities by varying heating and cooling at different rates. This is called heat treating. 

That brings us to today's subject, the composition and structure of steel.

If last week was why, and next week is how, today will be more or less whathappens in heat treating. 

This guide will focus only on simple carbon steels, and not more complicated tool or stainless steels. If you wish to learn about those, a solid foundation of knowing carbon steel is again imperative. 

We start with the question, what exactly is steel? Steel can be defined as an iron based alloy containing carbon, and often a few other elements. Alloy, for the record, means a metal containing two or more elements. 

For knife making purposes, we are concerned with two types of steel: Mild steel, and Carbon steel. Carbon steel generally contains .3%-1% carbon by weight, and mild steel is generally anywhere below that, for our intents and purposes. Carbon steel is more specifically defined by the ability to harden. So, only carbon steel (also known as high carbon steel) can be used for blades. 

As you've probably guessed by now, steel requires a certain amount of carbon in order to be manipulated properly. So with that in mind let's get down to steel structure. 

Steel Structure

Steel, or iron specifically, generally takes on a specific atomic structure. Think of it as a lattice of cubes: one iron atom at every corner of the cube, and another atom in the center. Other atoms such as carbon are floating in between. This is called Body Centered Cubic, or BCC. 

Now, something extremely important to keep in mind is that this structure forms over a three-dimensional plane. In a given chunk of steel, you will have some areas where the lattice structure is oriented one way, and some where the lattice is oriented a slightly different way. These chunks, or grains, defined by specific orientation in which one atomic cube is connected to the same plane as the one across the grain, can be of varying sizes, from coarse sand size to almost powder. The border between two grains will be a weak point. A bar of steel with smaller and more numerous grains will require much more force to break than a bar with larger and fewer grains. We will get further into this in future articles, especially on normalizing, but this information is enough for now. 

BCC (Body Centered Cubic) is the standard formation for steel at room temperature. But, as soon as you heat it to roughly 1600 degrees Fahrenheit (varying from one alloy to another), grains of different atomic structure begin to grow and form at the borders of the BCC grains.

These new formations are again cubic, but instead of one atom at every corner and one in the center (BCC), they are comprised of one atom at every corner, and one atom at the center of every face. This is called Face Centered Cubic (FCC). So, while a BCC cube will have 9 iron atoms, an FCC cube will have 14. 

Like I mentioned in the previous article, this transformation is a phase transformation. Turning liquid water into a solid (ice) is one phase transition, turning liquid water into water vapor is another. Now while these two examples are liquid-solid, and liquid-vapor, the BCC to FCC transition is a solid-solid phase change. They each have specific temperatures at which they change, based mostly upon composition. 

The temperature where the steel is transformed from BCC to FCC is known as "Critical Temperature" among knife makers. An interesting thing to note is that as soon as this phase change happens, the steel loses its magnetism. So as a bladesmith, you can tell when you've reached the right temperature by touching the steel with a magnet. If it sticks, you're still BCC. If it doesn't, you've reached Critical and the steel has transformed to FCC. 

Make sense?

Now, the following gets more complicated the more one studies, but for a basic understanding, I am keeping it simple to suit our needs for basic heat treating. If you heat from room temperature to critical, you transform from BCC to FCC. If you let the steel cool slowly from Critical down to room temperature, it will transform from FCC back to BCC. The key word there is "slowly". If you can cool the steel quickly enough, and go from critical to a certain lower temperature fast enough, it's not merely changing to BCC. 

So what does happen? Let's go back to the structure. 

Remember, BCC are smaller compact cubes with carbon atoms floating in between one cube and another. FCC are larger and more spacious. So when the steel is converted to FCC, the carbon atoms slip inside the cubes. If the steel cools quickly enough, the FCC switches back to BCC, transforming the cubes, compacting them, and becoming smaller. 

And the carbon?

The carbon atoms are stuck inside boxes too small for them. This creates a lot of stress, and grains with large amounts of carbon in them while other grains have comparatively little. This creates a very rigid, hard structure across the steel. The atoms are rigid in relation to each other: it is difficult to move them, but when they do, they break bonds rather than deform

If you recall the previous article, this should seem familiar. Hard, but brittle. 

This pressure and stress may be removed by heating to a significantly lower temperature than critical, roughly 350-450 degrees Fahrenheit. This can be thought of as opening up the BCC cubes just a bit to relieve "pressure". The hotter the temperature, the softer the steel. 

To recap: 

Steel at room temperature is generally in Body Centered Cubic formation. Heated past critical temperature, BCC converts to FCC, or Face Centered Cubic. A fast enough cooling will revert formation quickly enough to "compress" and put pressure on the carbon atoms by trapping them in too small of cubes. This converts the steel to a very hard but brittle structure. This can be relieved to a varying degree by heating again, although to a significantly cooler temperature than critical. 

Next week, we'll be looking at exactly how this all applies and how we, as knifemakers and bladesmiths, or really anyone who works with steel, can use this knowledge to make the most physically capable blades and tools possible, through very simple means.

Remember, knowing the why and the what is the secret to knowing the how
 

Caleb Harris

I’ve always fooled around with tools and hardware, but I think my passion with blades started far back in my childhood: wooden swordfights with the neighborhood kids. I became the neighborhood “blacksmith”, using my grandfather’s tools to hammer little crossguards onto wooden sticks. I always tried to find the best scrap wood: lightest, strongest, trying to get the perfect length and shape for each “customer”. This started my passion with blades.
 
When I was ten years old, I joined a local rock and gem club, learning stonecutting and cabbing, and through that came to take silversmithing lessons from a local jeweler. It wasn’t until around the age of 13, that I turned my attention to bladesmithing, which has captured my heart. 
 My personal obsession with bladesmithing, as I’m sure you can relate, isn’t just the joy and passion of the making: the musical clang of the hammer on steel, the shower of sparks on the grinder, the whisk of the blade over the sharpening stone, but also of the fulfillment in creating something that is twofold: that of beauty, and that of function. It’s trying to make something that is as much an art piece, as a tool that you can trust your life with. That’s what caught my heart, and the pursuit of that perfect combination still drives me.  

The Basics of Heat Treating, part I

 

This is an primer on the basics of heat treating, which is a rather fascinating science full of mystery. Rather than tell you what to do in a step-by step process, I find it's far more beneficial to give you a look into the steel itself and explain what's actually going on. This helps for testing, for altering, and for troubleshooting and gives you a feel for what is likely to happen in any given scenario. 

So, basics basics. Let's start with a fairly simple question.

What physical qualities make a high-performance blade?

Much of it has to do with geometry and the angles of the bevels and shape of the knife, but right now we're interested in the physical characteristics of the metal itself. 
 

  • A good blade will need to have the ability to be made exceptionally sharp. 
  • A good blade will need to have the ability to retain that sharpness after repeated use. This is generally known as "the ability to hold an edge".
  • A good blade will need to have the toughness to not break under stress. Preferably, to spring back to position rather than break or take a set (or bend).


We can disregard the first point for now, as it is directly related to the other two. Now, this is an important principle. In general, there are two physical qualities at opposite ends of a spectrum that steel can possess. 

The first is Hardness. In essence, hard steel is made up of molecules that are very resistant to moving without breaking bonds in relation to each other. This means it will break rather than bend, and chip rather than dent. A hard steel will hold an edge (not dull) very well, but it will be brittle. Hardness and brittleness are the positive and negative features of the same state. Think of a blade made of glass

The second quality is Toughness. In essence, the molecules are more fluid in relation to each other, and in stress they will modify position rather than break a bond. This means it will bend rather than break, and dent rather than chip. A tough blade will not break under stress, but it will dull very easily. Think of a blade made of copper

Now these two qualities are on a sliding scale. The tougher a blade is, the easier to dull it will be. The harder a blade is, the more brittle. Ideally, we want a blade that is somewhere in between. We want a blade that will hold a sharp edge through lots of use, and we want a blade to stay tough and strong through lots of impact and stress. 

These two qualities are of course not the be all end all, but they are a huge indicator of what exactly the goal is in heat treating. Remember, the technological progression of humanity is always about making it better; more efficient, prettier, easier and cheaper to attain. In handmade knives, easier and cheaper often goes out out the window because we are focused on making it the best. If you keep the principles outlined in this article in mind, then you begin to see why and how different materials for blades were used and replaced throughout history. But especially, these principles show you exactly where the end goal in heat treating is. 

Next article (probably next week), we'll look very in depth to the molecular structure and composition of steel.

P.S.,

Just a tidbit for you to chew on for next week: steel is an alloy that has many phases. We are used to the common phases of water: namely, Ice (solid), Water, (liquid), and Water Vapor (gas). You may have heard of a fourth phase: Plasma. Steel however, has sub-phases, which are all solids. Manipulating these phases and the transitions between them is the secret to a high-performance blade. And, just like water, they are manipulated by heating and cooling, and proper timing.

Caleb Harris

I’ve always fooled around with tools and hardware, but I think my passion with blades started far back in my childhood: wooden swordfights with the neighborhood kids. I became the neighborhood “blacksmith”, using my grandfather’s tools to hammer little crossguards onto wooden sticks. I always tried to find the best scrap wood: lightest, strongest, trying to get the perfect length and shape for each “customer”. This started my passion with blades.
 
When I was ten years old, I joined a local rock and gem club, learning stonecutting and cabbing, and through that came to take silversmithing lessons from a local jeweler. It wasn’t until around the age of 13, that I turned my attention to bladesmithing, which has captured my heart. 
 My personal obsession with bladesmithing, as I’m sure you can relate, isn’t just the joy and passion of the making: the musical clang of the hammer on steel, the shower of sparks on the grinder, the whisk of the blade over the sharpening stone, but also of the fulfillment in creating something that is twofold: that of beauty, and that of function. It’s trying to make something that is as much an art piece, as a tool that you can trust your life with. That’s what caught my heart, and the pursuit of that perfect combination still drives me.  

Stonewash Finish

  I have a personal obsession with "inset" scales. This particular blade, still a work in progress, does well with the stonewash. This steel is reclaimed saw blade steel which was heavily rust pitted. The texture from the pitting on the flats contrasts extremely well with an inset scale style handle, all the while remaining simple and rough but stark. Once the scales are highly polished it'll really pop

I have a personal obsession with "inset" scales. This particular blade, still a work in progress, does well with the stonewash. This steel is reclaimed saw blade steel which was heavily rust pitted. The texture from the pitting on the flats contrasts extremely well with an inset scale style handle, all the while remaining simple and rough but stark. Once the scales are highly polished it'll really pop

 

There's a number of possible blade finishes, from machine, to hand-sanded satin, to polished. A slightly less common one that you've likely seen is the stonewash finish. The stonewash finish is basically a matte "utility" finish, especially useful for a knife that is likely to be heavily used and likely to get scratched. It looks closest to stone slate, from which the term "stonewash" comes from. 


As with all features, aspects, and possibilities with knives, whether you should stonewash or not of course depends on the design. Some blades lend themselves to it (especially utility and EDC knives), others do not. That's up to you. Some people absolutely hate it, some love it. 

I saw it, thought why not, and tried it out. Here's what I did. 

This particular finish is technically an Acid Stonewash. After finishing a few belt knives to 220 grit and a medium surface conditioning belt, I put them in standard household vinegar for an hour or so, taking them out to wipe off every fifteen minutes. The blades took on a gray finish, interesting in themselves but I had better plans. 

Next was relatively simple. I took a small bucket, filled it halfway with coarse sand (gravel is usually used), and stuck the blades in there. Then, I put on the lid and spent a good five minutes shaking vigorously, quite a workout in itself. The gravel marks and evens the acid-induced oxide, speckling the gray with silver. 

Have you ever tried to do a stonewash finish? Have any tips and insights you found out in the process? Email me and I'll share it next article!

Caleb Harris

I’ve always fooled around with tools and hardware, but I think my passion with blades started far back in my childhood: wooden swordfights with the neighborhood kids. I became the neighborhood “blacksmith”, using my grandfather’s tools to hammer little crossguards onto wooden sticks. I always tried to find the best scrap wood: lightest, strongest, trying to get the perfect length and shape for each “customer”. This started my passion with blades.
 
When I was ten years old, I joined a local rock and gem club, learning stonecutting and cabbing, and through that came to take silversmithing lessons from a local jeweler. It wasn’t until around the age of 13, that I turned my attention to bladesmithing, which has captured my heart. 
 My personal obsession with bladesmithing, as I’m sure you can relate, isn’t just the joy and passion of the making: the musical clang of the hammer on steel, the shower of sparks on the grinder, the whisk of the blade over the sharpening stone, but also of the fulfillment in creating something that is twofold: that of beauty, and that of function. It’s trying to make something that is as much an art piece, as a tool that you can trust your life with. That’s what caught my heart, and the pursuit of that perfect combination still drives me.  

Grain Structure

 

Have you ever seen the surface of a broken piece of steel? Chances are you have, especially in this craft. You'll notice it doesn't break like glass, or splinter like wood. It's closer to tile or concrete; the broken surface will be a grainy texture with varying grain size (which, by the way, is important to the strength of the steel, so keep that in the back of your mind). 

Grains, is exactly what this is. Let me break it down for you (pun intended). 

The atomic structure of iron is like a lattice; imagine a cube, with one iron atom at every corner and one in the center. The corner of one cube also forms the corner of another cube, so it's a continuing lattice, with iron atoms continuing at right angles to each other in three dimensions. A group of iron atoms, all linked together in this formation, is a single grain. 

The only reason a large bar of steel is not all a single "grain", is because one groups of atoms on one part of the bar will form their formations at a slightly different angle to one at the other. The place where grain A and grain B intersect then, is a weak point. And if enough stress is put on the steel to break it, it will be along these intersections. Thus, when you look at the broken surface of steel, you can see these boundary lines. 

Note: another way to see these grains, and perhaps the one most used for study, is to cut and polish the surface of the steel, then etch it with acid. Because some grains are orientated one way, and another a different way, the surface of one grain will etch away faster than another, making the surface of different levels depending on the grain. This will then show up under a microscope.  

The smaller yet more numerous the grains, the stronger the steel will be. The process of normalizing, which you are likely familiar with, changes the iron from "Ferrite" (it's natural room temperature formation state), to "Austenite" by heating to around 1600 F or so, then left to air cool. Every time it reaches the transitioning temperature, new grains from along the borders of the old. Heating and letting air cool results in the formation of multiple new grains, which are small yet numerous. I'll get into the details of the why's and how's of normalizing in a future post. 

For now, this should give you a full understanding of what grains are, and the true atomic structure of steel. Having a deep understanding of the scientific portion of bladesmithing gives you an intuitive knowledge of the steel, which helps with troubleshooting, estimating time and deforming rates, and exactly what you need to do to get the results you want.

Caleb Harris

I’ve always fooled around with tools and hardware, but I think my passion with blades started far back in my childhood: wooden swordfights with the neighborhood kids. I became the neighborhood “blacksmith”, using my grandfather’s tools to hammer little crossguards onto wooden sticks. I always tried to find the best scrap wood: lightest, strongest, trying to get the perfect length and shape for each “customer”. This started my passion with blades.
 
When I was ten years old, I joined a local rock and gem club, learning stonecutting and cabbing, and through that came to take silversmithing lessons from a local jeweler. It wasn’t until around the age of 13, that I turned my attention to bladesmithing, which has captured my heart. 
 My personal obsession with bladesmithing, as I’m sure you can relate, isn’t just the joy and passion of the making: the musical clang of the hammer on steel, the shower of sparks on the grinder, the whisk of the blade over the sharpening stone, but also of the fulfillment in creating something that is twofold: that of beauty, and that of function. It’s trying to make something that is as much an art piece, as a tool that you can trust your life with. That’s what caught my heart, and the pursuit of that perfect combination still drives me.  

Trading Your Work

 

At the beginning of human civilization, people would trade for whatever they needed. If a farmer needed a new shovel, he would trade a few bushels of grain to the local smith. The only problem that arose was when the blacksmith didn't need grain, so the farmer would have to find something the smith wanted, trade grain for that item, then use that item to trade for the shovel. Eventually, the idea of currency was developed. The farmer could trade five silver coins for the shovel, and the smith could trade the coins to anyone else. 

This is the basis of barter, and how currency was developed. However there are still a lot of advantages to trading a good for a good, rather than selling for cash, especially for starting makers. 

First of all, currency (money) is only needed when person A wants something person B has, but person B doesn't want what person A has. If they both are interested in goods owned by the other, there is absolutely no need for cash (unless if the two items are not worth the same). If I bought Tom's pellet gun for $75, and he bought a knife from me for $75, cash really hasn't changed hands. This is, of course, as long as the two items are of equal worth. 

Next, and this is the really important part, is that doing a trade between two makers is mutually beneficial. Instagram has shown huge success for many makers, whether knifemakers, leatherworkers, jewelers, etc. 
If you ask me, it is the media outlet for functional aesthetic craftsmen. Many of you found the broke bladesmith through instagram, so I think it's safe to assume you use it. 

Anyway, the reason it's so mutually beneficial is this: you both get a feel for the marketing of the other person, and bring attention to the other person's work. Many artists, like leatherworkers or woodworkers, have the same target market (same people who are most likely to buy) that knifemakers do.

Thus, if I trade a knife for a nice wallet from Bill the leatherworker, he will post my knife on his page. Many of his followers will then come see my page, and maybe even follow. I do the same for him. This is a huge source for followers, and it shows potential customers that you are trustworthy, friendly, open, and negotiable. 

Second, I can take observation from his work; the weight, little details, especially the way he both packaged it, and the "feel" about it. Is it rustic and tough, or more of a subdued "gentlemanly" feel, or maybe he's got a fresh, clean and snazzy modern feel. If your work has a similar feel, you can use his as a reference point to tweak yours. 

All in all, trading does everything except immediately put cash in your pocket. It increases your following, your trust, you're more likely to make a trade that's worth it to you than a sale (at least at first), your opening for future collaborations (say a woodworker selling you display cases which then boosts your knive's worth), and especially, it gets your work out into the world, and into use. From there, if your work is good, the tradee will publicly say so, and boost more following, potential traders, and then sales. It's a rapidly increasing good situation. 

Caleb Harris

I’ve always fooled around with tools and hardware, but I think my passion with blades started far back in my childhood: wooden swordfights with the neighborhood kids. I became the neighborhood “blacksmith”, using my grandfather’s tools to hammer little crossguards onto wooden sticks. I always tried to find the best scrap wood: lightest, strongest, trying to get the perfect length and shape for each “customer”. This started my passion with blades.
 
When I was ten years old, I joined a local rock and gem club, learning stonecutting and cabbing, and through that came to take silversmithing lessons from a local jeweler. It wasn’t until around the age of 13, that I turned my attention to bladesmithing, which has captured my heart. 
 My personal obsession with bladesmithing, as I’m sure you can relate, isn’t just the joy and passion of the making: the musical clang of the hammer on steel, the shower of sparks on the grinder, the whisk of the blade over the sharpening stone, but also of the fulfillment in creating something that is twofold: that of beauty, and that of function. It’s trying to make something that is as much an art piece, as a tool that you can trust your life with. That’s what caught my heart, and the pursuit of that perfect combination still drives me.