Our guest author for the next two weeks is Todd Gdula, a professional bladesmith and member of the American Bladesmith Society. He does custom work and his website is www.toddblades.com.
One of the questions most asked of knifemakers is “What’s the best steel for a blade?” The correct answer is, “It depends on what kind of knife it's for.”
Volumes could be written on this topic, but today we’ll make it short and simple by only talking about blade steel choices for a survival knife, and a general purpose survival knife at that. This is my opinion on what the best steel choice is if you can only put one knife in your bug-out bag.
To choose a steel, we first need to identify what the knife needs to do. A survival knife needs to be a jack of all trades and very reliable. It can potentially be used to chop and split wood, de-limb branches, gut and skin game; act as a pry bar or a hammer, and to defend yourself. That’s a pretty tall order, especially when you consider that each of these tasks has knives specially designed to do them.
There are three general categories of steel to choose from, and each category has many types of steel within it. The three categories are simple carbon steels, stainless steels, and high alloy tool steels. Some types of steel may fit in more than one category depending on whose definition you use.
Types of SteelsSimple carbon steels include what are known as the “10” series steels; 1045, 1050, 1060, 1075, 1084, 1095, etc., as well as the “O” and “W” series and 5160 and 52100. The 10 in the 10 series indicates that it’s low alloy – basically the 10 means it’s iron with whatever percentage of carbon; .45%, .5%, .6%, etc. The O stands for oil hardening and the W for water hardening. Neither is as simple as the 10 series, but the alloying is fairly low. The 50 series starts to have more alloying, but is still relatively simple. The 50 means it has some chromium; 51 is low chromium, 52 is medium chromium. The second two numbers indicate carbon content; .6% and 1% respectively. (Editor's note: see Firehand's post for a more in-depth discussion about what carbon content means.)
Stainless steels contain enough chromium so they form chromium oxide instead of iron oxide, which inhibits rust. Stainless is a large and varied group; 420, 440, CPM154CM, 12c27, ATS34, and on and on. By definition – which is also somewhat variable, stainless contains at least 10.5% chromium, but some types approach 20%.
High alloy tool steels have lots of stuff added to the smelting recipe and most were created for a specific purpose. They include the “A”, “S”, “H “ and “D” series, Vascowear, and overlap into some of the stainless types, as well as 52100 and some others. The A stands for air hardening; the S for shock resistant; the H for heat resistant; the D for die steel and Vascowear is a high vanadium wear-resistant alloy.
Which Steel to Use?So it comes down to a process of elimination. I’m going to eliminate the high alloy tool steels first, because they have very specialized properties and we’re looking for a jack of all trades.
Next to go are the stainless steels. I can hear the outrage, so I’ll explain. The only advantage stainless has over non-stainless steels is that it’s rust resistant. And believe it or not, that’s not that important. However, it has two disadvantages that to me are very important: First, when it's heat treated, it through hardens, which means that the whole blade must become the same hardness. Second, compared to other steels, it’s not suitable for big blades because of its relative brittleness
We’re down to simple carbon steels then, and while there are several good choices here, there is one stand out: 5160. The main reason for this is it can be differentially hardened, which means that the edge can be made very hard and the spine fairly soft. This is important because it makes the knife very tough:
- When subjected to lateral forces it will bend, rather than break.
- You can strike the back of the blade with, or against, hard objects and it will deform rather than chip.
- You can make a very large (even sword sized!) blade from it and it can handle tremendous chopping stresses.
- You can easily sharpen it with a rock.
- While there are a number of steels in its category used to make springs, 5160 is the spring steel.
While there are other good choices, 5160 is, in my opinion, the best all-around steel for all the things a survival knife has to do.