Knifemaking

Intended cutting use and blade style help determine the ideal alloy for you and your knives.

Three critical aspects of creating or choosing a quality blade are steel selection, heat treatment and geometry. This feature focuses on the first of these, and the first any aspiring knifemaker or enthusiast will be tasked with—choosing the right blade steel for you and your knives.

To the casual observer, the steel selection process wouldn’t seem like such a big deal, but as in-depth as this article is, it barely scratches the surface of the topic.

Not all steels are created equal. Each varies as much as knife style and is designed for a specific application. So, matching the correct steel to the specific blade, intended use, and maker or user can be critical in creating a quality tool. Choosing the best alloy for your purpose can mean the difference between achieving the highest performance by effortlessly allowing the steel to do what it does best and struggling to pound a square peg into a round hole by forcing it to do something it was never designed to accomplish.

From my observations after a lifetime of providing metallurgical consulting services for various industrial clients and countless knifemakers, the latter rarely select steel with the same analytical vigor as the former. Rather than independent research to match steel chemistry to a process and product, knifemakers often choose whatever alloy everybody else is using.

Be it a ubiquitous old favorite or the newest rage in the “steel of the month club,” no single alloy is the best fit for every knife, use or maker. On the other hand, the one area where knifemakers often exceed my industrial clients is letting frugality make the choice. The number of knifemakers who have told me they use a specific type of steel because of their access to a cheap or free supply is unfortunate.

The trouble with these approaches is needlessly steepening the learning curve for many a new maker or knife user. I can’t count the number of times I have heard a frustrated knifemaker state that an alloy they have tried is a bad steel. But there is no such thing as bad steel. Industry wouldn’t bother wasting time, effort or money on steel that wasn’t optimum for its intended purpose. There are poor application choices and bad heat treatments. Any fault lies with the knifemakers or bladesmiths and not the steel.

A36 is an excellent steel choice for use in buildings and bridges, but it is a bad reflection on knifemakers if they insist on making a blade with it. The steel properties of A36 are not conducive to knife blades. Alloys like 1095 or O-1 can make good hunting knife blades, but if the steels are heat treated like 5160, they won’t measure up in edge performance. I can’t tell you how often I’ve bitten my tongue when shown a blade fashioned from steel with barely enough carbon for adequate strength or an abrasion-resistant edge.

If knifemakers have to deviate from standard heat treatment practices with unorthodox extra steps, it is most likely the result of a steel choice that does not match their application or methods. You can under-soak or over-temper a 1% carbon steel sword or use an alloy better suited for such a blade. You can add several steps to heat-treating richly alloyed steel in your forge or choose a steel that readily responds to that heat source.

Intended Knife Use

The problem is that we often proceed from the wrong direction. Whatever the reason, many knifemakers have already settled on their steel before determining what knife they will fashion, but how can you make the right choice in a material before you even know its intended use?

A better model for success is letting the primary tasks a knife is meant to perform determine needs and goals. Develop a plan to achieve those goals by designing a hand tool that will perform a specific task or even multiple tasks, keeping in mind that the intended uses of a single knife can be much more varied than people think. With the desired tasks for the edged tool in mind, choose the material based on the desired properties inherent to each steel’s specific chemistry. Equally important is recognizing the limits of a maker’s abilities to work with a given chemistry.

To explain how to choose the correct steel for you and your knives, the myriad of blade designs is distilled down to two primary categories. The first group—fine-cutting knives—is designed to perform keen slicing or aggressive slashing. They are most often used in a draw-type cut that is optimized like a saw at the microscopic level. Think of scalpels, skinning and hunting knives, and many kitchen knives. Their edges are thin, flat or hollow ground for cutting various soft, fibrous materials.

This group has a subcategory of blades, including some kitchen knives and razors, that will be identical in many design features and desired properties, but they are used more in a push cut. Regardless, impact toughness is not nearly as crucial as abrasion resistance for knives like this.

In contrast, the second group—choppers—is used in straight-on, push-type motions, cleaving, or cutting that often involves impact. These knives cut more like a chisel than a blade drawn into a cut like a saw. Camp knives, some bowies, and many swords fall into this category. They benefit from polished, beefier, convex edge grinds that don’t require abrasion resistance as much as impact toughness.

By definition, a knife is a cutting tool. If we should ever find ourselves detracting from a blade’s ability to cut in any part of our plan or execution thereof, we may need to consider whether making a knife or another tool is the better option.

Thus, all the properties discussed herein are relevant to cutting. A fundamental condition for a blade to slice through material is that it must be stronger than the cutting medium. There is tremendous load pressure at the microscopic level, where the cut is initiated. So, almost by definition, strength must be a top priority in any knife edge.

For this article, strength is the ability to resist deformation under load. Opposing this prized quality of strength is ductility, or the ability to easily deform without edge or blade failure. Knifemakers heat treat steel to replace ductility with strength. For millennia, it was the job of the blade maker to find the most acceptable compromise between strength and ductility for their blades to cut while avoiding brittle failure.

Steel Strength

There are many types of strength in steel. Examples are compressive strength and tensile strength. These and shear strength are not as apparent in general knife use, so knifemakers more easily conceptualize them as hardness.

The other quality prized in a blade is toughness, which should be viewed as the steel’s ability to withstand shock from sudden loads rather than bending in a ductile manner under gradual load. These are two entirely different behaviors, with one being more relevant to a blade used in chopping. Rather than the Faustian bargain of trading strength for ductility, the Holy Grail of blade making is maintaining high strength with impact toughness. In chopping-type blades, impact toughness is almost as valuable as strength.

The next property to consider in a knife blade is abrasion resistance. Microscopically, the knife edge is subjected to tremendous wear, even when cutting seemingly soft materials. It is this wear that results in the tool dulling when used. Abrasion resistance is the steel’s ability to withstand such friction effects. While this property does increase with overall hardness, steel’s unique makeup gives it abrasion resistance above and beyond hardness and even independently from it. Within the steel, there might also be carbide particles with a hardness that far exceeds the overall Rockwell measurement numbers of the blade. Fine cutting and slicing blades benefit more from abrasion resistance than impact toughness.

Although the possible steel choices for modern knifemakers are endless, for simplicity’s sake, this discussion is limited to non-stainless alloys commonly used by forgers and grinders alike. Although many knifemakers have become dependent on AISI (American Iron and Steel Institute) or SAE (Society of Automotive Engineers) steel names, such titles as 1084, W-2 or 80CrV2 lack specificity and meaning compared to studying the individual steel’s chemistry in determining its potential properties.

I strongly encourage knifemakers to study the chemistry of any potential steel choices to decide which one to use and how to work it. A supplier that provides the chemistry for your steel understands this and is well worth doing business with rather than a source that omits the alloy’s makeup.

Carbon content is the first consideration within a steel’s chemistry and perhaps the most important. Carbon is the main element responsible for strength in steel. The more carbon a steel has, the greater strength can be achieved in hardening. However, this is only true to a certain point; maximum hardness in carbon steel is achieved at around .80% carbon, and beyond this, not much more is gained in that area. Putting more carbon than .80% into the solution during the hardening process can harm a bladesmith’s goals. However, carbon beyond this optimum level will add abrasion resistance if allowed to stay in carbide form.

This sweet spot in carbon levels around .80% is known as the eutectoid. It is the most efficient use of carbon in steel, with no leftover iron (ferrite) or any leftover carbide (cementite). Steels with less than .80% carbon content are inherently tougher and less brittle, while steels with more can have much greater abrasion resistance with a tendency to be less tough. This is important to consider when choosing steel for your intended blade purpose. Does a machete need abrasion resistance? Does a skinning knife need to be tough? Choosing 1075 for one or 1095 for the other could make all the difference in having a steel that will work for you or against you in creating that blade.

In centuries past, bladesmiths had no choice but to compromise between strength and ductility when working with simple iron-carbon material. But then, starting in the early 19th century, alloying changed everything. Finally, with the intentional addition of other elements to steel, bladesmiths could have their cake and eat it, too.

Steel Alloys

A sword in the 13th century that had to be kept in the low hardness ranges could now be just as tough at much higher hardness levels. Fine slicing cutters could have an abrasion-resistant carbide boost far exceeding simple cementite abilities. But with these gains in performance came greater demands for more precise controls in heat treating, atmosphere, and more refined blade quenches. Today, even the most basic carbon steels have enough alloys to radically differentiate them from the old steel. Anybody who thought they would water quench 1084, just like traditional tamahagane steel, can attest to this fact.

For this reason, another critical factor must be considered in proper steel selection beyond the type of knife being made. It is why the premise of this article is choosing the right steel for you and your knife. Our modern steel alchemists may have created the perfect high-tech steel for a knifemaker’s application. But if they’re learning the ropes, or all they own is a humble forge, it could still be a terrible choice for their knife.

If your shop is equipped with a digitally controlled oven, all the many modern alloy options are available if you learn the rules each steel choice requires. The same chemistry that makes one steel harden in almost any oil or air makes it much more finicky when heated before being quenched. An alloy steel may have the potential to outperform a simple carbon steel, but not if you lack the equipment necessary to unlock that potential.

Figure 1 shows the as-quenched hardness results of a series of tests involving simple heating versus a standard 10-minute soak on commonly used steels. Here, the effect of increased alloying is plain to see when looking at each steel’s time and temperature requirements, which many open-flame heat sources or forges may struggle to meet. Unless armed with an excellent understanding of the metallurgy, a smith desiring to stick with more traditional tools would be better served by more traditional steels. Simple carbon steels such as “W” or 10XX series are like what forges were initially made for and will allow the traditional smith to produce a fine blade effortlessly.

Knowing what each of the additional alloying elements brings to the table is valuable in knowing what to seek in steel. If you’re looking for impact toughness, consider chemistries that include nickel or silicon. These additions affect the iron’s atomic lattice, which acts like a shock absorber. For a knife needing abrasion resistance, a boost from the more powerful carbide formers can give you longer wear than simple cementite, with two of the most common examples being vanadium (above .25% of overall elements) or tungsten. Chromium will also help in this area to a lesser extent.

If you wish to achieve a fully hardened blade with minimal effort, manganese over 1% or relatively modest additions of chromium are just the ticket for leaving behind your stressful days of the water quench. And, of course, for applications where simple carbon steels would rust too quickly, chromium over 11% will also help resist corrosion.
The chart in Figure 2 brings together all these considerations. On a final note, it must be conceded that a skilled bladesmith with a solid knowledge of heat treatment could push several of these alloys into adjacent categories. Still, here, we’ve focused on the path of least resistance.

By capitalizing on the characteristics of an alloy’s chemistry, a maker can spend less time getting it to behave in the desired manner and more time maximizing its performance.

More On Knife Steel:

• Knife Steel Trends: What To Look Forward To In 2025
• Knife Steel Alloys: A Down-And-Dirty Guide
• Damascus Steels: What To Use And When