“If I Had a Hammer (Hammer Song)” is a little tune that defined a movement and a generation, a ditty with a killer hook and deceptively simple lyrics. Though Peter, Paul and Mary popularized it when they covered it in 1962, “If I Had a Hammer” was penned with a greater purpose in mind than merely topping the charts. Pete Seeger and Lee Hays, a pair of artists with strong political opinions and purported ties to Communism (although the jury is still out on the depth of their connection to that particular movement), definitely had a message to communicate. The desire to hammer out “danger” and “a warning” and takes on a different tenor when you consider its authors’ backgrounds. However, the song’s cultural prominence, manifold covers by diverse artists, and plain diction have caused it to take on a different, more proverbial meaning: To a man with a hammer, every problem looks like a nail. Such a thought would’ve likely made Seeger and Hays blanch, but just consider the obvious silliness of lines such as “I’d hammer out love between my brothers and my sisters / All over this land.” Real-life problems rarely get rectified through singular solutions.
Something similar is true when dealing with knives, be they folding pocket knives or OTFs. There’s no singular best length, grip material, or specific sort of blade steel. Every material choice represents a tradeoff between various factors. In this article, we will discuss the various reasons why steel selection matters, different qualities of steel that you ought to be aware of, and specific steels that work well in many different sorts of blades.
Why Is Steel Selection Important?
“Artistic unity” is an idea in various kinds of creative endeavors that emphasizes the importance of the various parts of a painting or novel or song being arranged in a specific way so that they harmoniously mesh. In other words, they become more than the sum of their parts. This idea holds true across multiple fields, knife design included. There’s something magical about how a blade’s elements combine to create a truly unique tool. But unlike a poem, picture, or a pastel, a knife depends utterly on the quality of its materials, so much so that any reduction in them can pose an existential threat — particularly when it comes to steel.
Steels seem simple on the surface. As alloys comprised primarily of iron and carbon with tiny percentages of other elements, different kinds of steels have existed since at least 1800 BC. Over time, though, smiths have honed their understanding of this metal and learned to alter its essential characteristics by varying the ratio iron and carbon, as well as by introducing elements such as chromium, cobalt, manganese, molybdenum, nickel, tungsten, and vanadium. Such changes can yield a knife that can thrive in harsh, damp environments or one that holds an edge far longer than other options.
That being said, no knife blend can give you everything. Make a poor decision, and you may end up with a knife that’s soon stippled with rust. Or that needs sharpening nearly every time that you use it. Or that simply snaps on you. That’s why it’s important to understand the various characteristics of steel and their importance relative to different kinds of tasks.
What Are the Attributes of Knife Steel?
The key to finding the “best” knife steel is to match its innate attributes with whatever task you’d like to perform. Are you considering a knife for everyday carry? Backwoods use? Self-defense? Filleting your latest catch? Perhaps you just want a beater blade that you can put to hard use and easily sharpen when it inevitably dulls. Whatever you’re looking to do with an OTF or any other knife, you need to see where it intersects with the natural qualities of its steel.
Whenever you try to place any technical subject into categorical boxes, you will run into experts who disagree, and the same holds true when discussing the attributes of knife steel. We will talk about knife steel having five attributes, but don’t be surprised if you find others highlighting slightly different qualities.
With that said, the first and most obvious quality of knife steel is its …
Hardness
Hardness is easy to define, but it’s often confused with other characteristics in this list. According to an archived article from the University of Maryland’s A. James Clark School of Engineering, hardness is the “resistance of metal to plastic deformation, usually by indentation. … The greater the hardness of the metal, the greater resistance it has to deformation.” The technical way by which one measures hardness is with the Mohs scale.
The eponymously named scale was Invented over 200 years ago by one Friedrich Mohs, a German scientist who initially trained at the University of Halle. Mohs assigned arbitrary numbers ranging from one through 10 to minerals in ascending order of hardness and then seeing if they could make a non-plastic deformation (i.e., a scratch) on an unclassified material. Mohs then ranked the various materials, creating a practical scale where super-soft metals such as potassium have low numbers like 0.4 and the hardest like titanium carbide have high numbers like 9.3.
About a hundred years later, a pair of Americans named Hugh Rockwell and Stanley Rockwell used a similar process to make the not-so-creatively named Rockwell test. While the test measures the hardness of materials by creating a scratch like the Mohs scale, it also has complicated alphanumeric coding that sorts materials into various classes and then applies different levels of corresponding force using a specific indenter.
On the Mohs scale, most steels rank somewhere between 4.0 and 4.5, and the Rockwell test done by a Rockwell hardness tester will typically measure them on the HRC scale, which will include a number after the prefix. For both measurements, a higher number indicates greater hardness. (Note that knife makers will often drop the “HRC” designation for the Rockwell test and simply list denote a blade’s hardness using a plain number. Again, higher means harder.)
Toughness
Though you might expect hardness and toughness to serve as synonyms for each other, they actually describe subtly different things. Whereas hardness deals with how much force a material can withstand before it undergoes non-plastic deformation (i.e., a change in shape that can’t be reversed), toughness is a measure of its ability to absorb energy without breaking.
The technical measurement of hardness is the the Charpy V-notch test, which involves taking a square metal sample of a particular metal that measures 10 mm by 10 mm, machining a notch on its face, and using a pendulum to swing a hammer at the material with increasing increments of force until it fractures. Hard steels can sometimes be brittle and suffer from decreased toughness.
Ductility
The term ductility isn’t as commonly used as hardness and toughness, but it describes a related concept. When metals are subjected to tension, some of them will stretch and deform rather easily whereas others will break. A ductility measurement will quantify just how much a metal can be drawn prior to fracturing. There are at least eight different industrial ductility standards.
Edge Retention
“Edge retention” means exactly what you might think: It measures how long a knife can cut prior to losing sharpness. This quality is usually positively related to hardness, and while many hard knives may keep an edge for an exceedingly long time, they can also prove harder to sharpen once they inevitably become dull.
Corrosion Resistance
When time and moisture combine with steel, the result is oxidation, the consumption and destruction of the metal through its transformation into rust. Specific types of steel excel at resisting rust. However, they often exhibit decreased hardness and edge retention.
Excellent Applications for Specific Knife Steels
To go back to our song example in this article’s introduction, knife steel has more in common with The Rolling Stones’ 1969 classic “You Can’t Always Get What You Want” than Seeger and Hays’ hammer. Finding the best knife steel has less to do with discovering an ideal formulation than measuring the tradeoffs between hardness and toughness, corrosion resistance and ductility — and price. In an ideal world, we’d be able to achieve top marks in every area, but this is reality. We can’t always get what we want, but through careful analysis, we can get what we need in a knife steel.
Following is a list of different kinds of knife steels, their characteristics, and how you’ll typically find them used.
440C
The most basic steel on the block is good old 420 stainless steel, which provides excellent toughness and corrosion resistance at the expense of low edge retention. It’s a cheap option intended for hard-use knives where you don’t care if they get banged up a bit. But what if you wanted a somewhat more balanced steel that didn’t carry a premium price tag? Enter 440C. Slightly more expensive and with a little less toughness than 420, 440C was once a top-tier premium steel. It’s much more common today, but also a good option for EDC knives that you don’t plan to use in survival scenarios.
1095
Passably tough and incredibly easy to sharpen, 1095 steel owes its qualities to the nearly one-percent carbon content in its composition. Due to the way in which it resists breaking and how easy it is to hone it to near razor sharpness, 1095 has developed a following among outdoorsmen and backwoods types. The main drawback of this type of steel is its tendency to corrode when exposed to moisture. If you want to use 1095 in your blade, you will need to regularly clean and oil it after use.
D2
In the past, D2 was dubbed a tool steel due to its toughness and subsequent use in, well, tools. Though it doesn’t technically qualify as a stainless steel, it does resist corrosion much better than 1095 while remaining very hard and holding its edge for extended periods. But when you need to sharpen a blade of D2, expect difficulties. While it may stay sharp for a long time, D2 requires quite a lot of effort to put a keen edge on it. A good steel for hardworking blades. Check out the TacKnives Double Action OTF, which is just one of the knives we offer with D2.
A2
A2 also started its life as a metal intended for tools used in woodworking, plastics manufacturing, dies, planer blades, and more. While experts are divided about exactly when A2 came to the market, it is an older steel formulation, and Larrin Thomas of Knife Steel Nerds argues that early examples of this steel existed prior to 1940. The main metallurgical differentiator of A2 is its relatively high carbon and vanadium content, which makes it hard and easy to hone it to an incredibly sharpness. A2 turns up in combat knives and survival knives. Note that will dull quickly and is prone to corrosion
154CM
Like D2, 154CM wasn’t initially intended to serve as a knife steel. Instead, Crucible Industries (its creator) made it for use in the manufacturing of jet turbines. But this mid-level steel is just as balanced as its price, earning high marks for edge retention, corrosion resistance, and ease of sharpening. It is slightly less tough than other options, but remains far from brittle. We use 154CM in several of our knives, such as our TAKCOM-branded Hornet.
AUS-8
Japanese steel manufacturers have a reputation for creating high quality and somewhat exotic steels. AUS-8 doesn’t so much put the lie to that impression as nuance it. This steel shares some similarity with 154CM, functioning as a well-rounded metal with easy sharpening, the ability to stand up to rust, and robust hardness. It does have a tendency to lose its edge, though, and AUS-8 can see its fundamental properties change for the worse if poorly heat treated. This is a very good steel, but you should make sure that you’re buying it from a reputable knife maker.
M390
A premium knife steel, M390 is created by sintering, which is a process where powdered material gets simultaneously heated and pressed into a solid. Instead of employing an exotic blend of elements, it uses judiciously portioned amounts of molybdenum, vanadium, chromium, and carbon. This leads to a steel that excels in every area except sharpening. Unless you have specialized equipment, you will find it very hard to put a keen edge on an M390 blade. TAKCOM OTF The Shepherd comes with a blade of M390.
MagnaCut
MagnaCut may not quite be knife-steel royalty, but it comes darn close. Larrin Thomas, who we mentioned above in our A2 steel section, specifically formulated this steel with knife creation in mind. Almost entirely impervious to corrosion (at least as much as a steel can be), it also scores top marks for both toughness and ease of sharpening. Surprisingly, it also enjoys average edge retention, a rarity for easy-to-sharpen blades. The only downside to MagnaCut is its rarity and concomitant expense. Our TAKCOM Barracuda OTF incorporates MagnaCut in its design.
We use high-quality steel in both our TacKnives and TAKCOM brands. Check out our selections today!
