The Truth About Blade Steels
What is the soul of any knife? What defines a blade as a knife? Sure, boxcutters do many knife related tasks, but are they knives or simply edged tools? I would argue that the importance of any knife style and design lies in its heart and soul. The steel.
Hello, my name is William Woods and I am a knife maker . . .
Since The Truth About Knives is just taking its first steps this week, Chris Dumm and I thought we would start things off properly and start a discussion about blade steel. Now enough of the introductions: let’s talk blades!
The single most asked question is always, “What is the best steel for a knife?” Well, like all simple questions the answer is far from direct and concise. Choosing the steel that fits your needs is kind of like picking a car. Can you tow a horse trailer with a Porsche? Sure. Will it perform terribly and eventually fail? Yes, yes it will. The most common complaint that leads many to bad-mouth a certain alloy of steel is to try and force one type of knife to perform tasks it is ill suited to.
Three things determine the “performance” of any cutting blade. Blade geometry (the style and shape of a knife), alloy (the particular mix of steel), and the heat treatment (the process used to harden the alloy). In this article we will be discussing steel alloys and their performance characteristics.
OK, so the big first distinction most people are familiar with are “stainless” and “carbon” steel. These are slight misnomers, considering that stainless steel is only stain “resistant” and ALL steel has carbon in it. [Ed: if it didn't, it wouldn't be steel.] Semantics aside, it is generally accepted that to be considered “stainless” a steel alloy must contain 13% chromium. Now here is where it gets complicated. There are hundreds of steel alloys that are suitable for making knife blades and the individual composition of those alloys mean they can contain anywhere from 0% to 25% chromium. Great, let’s add a bunch of chromium and make the most super-duper stainless blade ever! Right? Hold on: unfortunately metallurgy is insanely complex, and the more chromium you add the worse the steel gets at important things like staying sharp and cutting things.
The point is that blade steel metallurgy is a delicate balancing act. Every alloy is made to balance corrosion resistance, edge holding, machining, wear resistance, and toughness. There is no magical unicorn horn steel that can live in salt water, slice paper all day, and cut down trees in its down time. It doesn’t exist.
Since we are talking about corrosion, let’s say you asked me for recommendations of corrosion resistant steels. I would say the most popular and highest performing stainless steels on the market today are 440C, CPM-S30V, 154-CM, 12C27, AUS-8. In no particular order these stainless steels offer superior stain fighting powers and will hold an edge if properly maintained.
So we have covered what puts the “stainless” in stainless steel. Let’s talk toughness. Toughness is a very particular metric. Specifically it means the ability of a material to absorb energy and plastically deform without fracturing. Knives that break are blades that have been pushed beyond the limit of that alloy’s (and heat treatment) capability. Many many elements contribute to the toughness of an alloy but commonly manganese, molybdenum, nickel, and silicon are used to control the hardness/toughness of an alloy. Toughness is typically a one way street. The tougher the steel the worse is holds an edge and vice versa.
Typically really tough knives made for extreme tasks like chopping, prying, and hammering are made with equally suited alloys. Some are very simple like the good ol KA-BAR. KA-BAR’s are made with 1095 steel which is essentially iron, .95% carbon, and .4% manganese. Tough, holds an edge, re-sharpens easily. All the things you want in a combat/survival blade. Like all things though technology has advanced the metallurgy field and more companies are releasing “super steels” with complex compositions and precise heat treating specs.
The king of the hill these days for tough steel alloys is probably CPM-3V. It’s expensive, semi-stainless (only 7.5% chromium), and practically bomb proof. I’ve personally cut dozens of card board boxes and then chopped down a 8” tree trunk into kindling and still been able to shave my arm. Amazing stuff, but leave it in a hunting bag in the back of a truck for a few hot and humid Georgia summer days and hello pitted rust! It is just not designed to resist moisture without constant oiling and maintenance.
So for the tough alloys we have discussed 1095 and CPM-3V. Is that it? Hell no! 5160, D2, INFI, SR-101, and CPM-S35VN are all great tough steels. Each alloy has its place and usefulness. They all have great toughness but many have varying degrees of wear resistance with brings us to…
Here is the most subjective part of any blade steel. Wear resistance or edge holding is difficult to measure as a metric. Most end users measure the time it takes for a knife to go dull. This can be misleading since on a microscopic level there are at least 4 different types of edge failure but that is a different topic for a different day. The old stand by tests of slicing paper and shaving hair are reasonably good metrics for testing sharpness so let’s stick with those.
Most blade steel alloys hardness is measured on the Rockwell C scale (from now on referred to as the RC). Most knives will register anywhere from 54-65 RC depending on alloy and heat treatment. Wear resistance refers to a blade’s edge holding capabilities. Some alloys can support finer thinner edges and will cut more easily. Some alloys take a “toothy” edge and consequently have nano-serrations that make excellent slicers but are poor for push cutting. So what chemically is making these alloys so hard? Well principally adding carbon increases wear resistance but vanadium and tungsten are commonly added to boost wear resistance. The basic principle is the formation of carbides during the heat treatment process to increase the hardenability.
So you can see getting a knife to be sharp and stay sharp is really a balance of the ability to take an edge and the strength to hold it. This is where the industry has really gone crazy in the last 20 years. Since higher and higher RC hardness steels have always been possible the issue was toughness. There is little use for a sharp brittle knife. Kershaw, Spyderco, and Benchmade have all been selling these super steels that boast never ending sharpness. ZDP-189, CPM-M4, S110V, and the current champ REX 121 (with an insane RC of 72) are all extremely hard steels that will outlast a more pedestrian alloy by 3 or 4 times before sharpening.
BUT…there always is a tradeoff. Sharpening a blade made of these exotic alloys is difficult. Quality sharpening stones are required and it is NOT for beginners. Coupled with the extra brittleness and general exotic nature makes knives made from these alloys more suited to very specific tasks. This also leads me to…
When customers are shopping for knives there usually is a limit. What’s the best knife for under $25/50/100/500? Well the moment you step outside the boundaries of “standard” industry steel and start shopping for more performance oriented alloys the prices start to rise. As a knife maker when I buy steel in bulk I pay by the pound. By weight a more common “mid range” stainless steel like 440C will cost 3-4X less than a more exotic alloy like CPM S30V. Add in the extra costs associated with machining, grinding, and heat treating exotic steels and you have a much more expensive knife.
It all comes down to perceived value. Is it worth it to you? Do you need a Spyderco Endura 4 with a ZDP-189 blade for $170 or would the VG-10 version for $100 be more than enough? These are questions every collector or enthusiast must make for themselves. I can say definitively though that when you have a knife you truly love in a steel that performs just as well you have something special. It is an intangible feeling of having the pinnacle of what science and design are capable of doing together in one package.
There are very few areas in our lives where we can honestly attain the absolute “best”. I will never be able to afford a Ferrari. I will never own an island or date a super model, or even own the finest 1911 man could want. But I can for $7-800 own one of the planet’s best knives, an elite group of people. That is the attraction of exotic super steels.
Country Of Origin
Now for every “What is the best _?” question comes “Hey check out my knife! I got it on Ebay / China / Pakistan / truck stop / flea market!” This is the moment when your unknowledgeable friend will attempt to impress you with their newly acquired stabbing implement. Hey, we were all 11 years old once so try and let them down easily.
Unfortunately, cheap and downright dangerous knock-off knives have been flooding the market for decades. The majority of which are made in China, Pakistan, or Indonesia. Now I will not say that a cheap import knife can’t cut well. I have been surprised 2 or 3 times in my life by a cheap Chinese knife. I have also been wildly unimpressed by HUNDREDS of crappy import knives. Many of these designs are so alluring because they 100% rip off designs from actual makers and manufacturers. (Anybody who collects Extrema Ratio or Rick Hinderer knives feels my pain) In many cases there are more fakes floating around than actual original knives, leading to some serious confusion.
“China pot steel” and “Pakistani car bumper” knives are also quite dangerous. Folding knife locks fail, blades snap, and they go dull faster than a knife fight in a phone booth. Honestly good knives can be had starting at $20. There is no reason to start diving in the “Bucket O’ Knives” at your local gas station.
We started this discussion by examining the question, “What is the best steel for a knife?” As you can see that is quite the loaded question. The only way to answer it is to ask some questions. What performance do you want from the knife? Will this knife be exposed to moisture? Will you be performing hard use tasks with the knife? What is your budget? These are some of the relevant questions that must be answered before a responsible answer can be made.
Well thanks for listening to me ramble on about steel. I hope you learned something or at the least weren’t terribly bored. I hope to post more of these articles in the future. If you want more please let us know in the comments. I will do my best to answer any questions you have in the comments as well.