11-21-2016

Knife Steel

Forget about the search for the "best" knife steel. It isn't about the best steel, but about understanding the strenths and weaknesses (pros and cons) of different steels. Every year there are several new "super steels" and there is no denying that it is interesting learning about them.

I am not a knife maker or a metallurgist. This is my own summary of what I have learned about knife steels. You can read about this topic at great length. Lots of people who don't know tell you what they have heard from other people who don't know.

One thing is certain. Proper heat treating is as important as the steel itself. All that most folks can do is to select a manufacturer with a good reputation and trust that they have people who know how to get this done right. The design and manufacture of the knife is almost certainly more important than what steel the blade is made from.

What is the best knife steel? Why, S30V of course. This is almost an honest answer, the real answer is that "it depends". S30V offers an excellent balance of toughness and edge holding hardness. it has also been around a long time, people know how to work with it and get the best out of it. It is well proven. S30V is the steel to reference all others to. For a folding knife, S30V is ideal, other steels are good and there are some new steels that may be better. I consider S30V as the first of the "super steels".

Note that the "super steels" with high vanadium content hold their edge very well, but are correspondingly a real task to sharpen. It is best with them (and with any knife) to keep them sharp rather than let them get dull and then try to get them sharp again. It has been said that S90V and S110V are almost impossible to sharpen.

I classify steels into the following categories.

Crappy steels

If you are spending decent money for a knife you won't see much in this category. 440 steel that is not explicitly labelled 440C could be considered in this realm. Any knife that doesn't designate the steel it is made of is almost certainly in this class.

Carbon steels

Steels like 1095 are non-stainless, but extremely tough and are ideal for chopping tools, machetes, tomahawks, and the like. If they are not used in a big chopping tool, you are probably looking at a cheap knife that will be easy to sharpen, but rust and get dull quickly.

OK steels

Here we have AUS-8, 440C, 8Cr13MoV, CTS BD1 and others. All good stainless steels. In general easy to sharpen and affordable. People say that AUS-8 and CTS BD1 and 8Cr13MoV are effectively the same steel. The claim is sometimes made that 8Cr13MoV is an "upgrade" to AUS-8. This is probably true and may have been a selling point when AUS-8 was in common use. These days, with steels like 154CM and S30V available, there is little excuse for using one of these steels unless the knife is offered at a low price. Steels in this class should be easy to sharpen and take a good edge. However they won't hold that edge as long as one of the super steels.

So you face a conundrum. Do you want an affordable steel that you can sharpen well (but need to sharpen more often). Or do you want a hard to sharpen steel that because you are unable to sharpen it, actually gives you a poorer but long lasting edge? The truth is that many people without advanced sharpening skills may actually be better served by a steel in this class than one of the super steels.

Great steels

Here we have S30V and 154CM. Both are wonderful steels. 154CM is essentially the same as ATS-34. ATS-34 is made in Japan (by Hitachi) and no longer exported out of the country. 154CM is used for some big blades where S30V is perhaps too brittle. VG10 is a japanese steel that is very similar to 154CM. You hear again and again how VG10 is easy to sharpen to a fine edge. You don't see VG10 as much as you used to though.

S35V is S30V with some niobium added. This makes it easier to machine, but is not especially better than S30V for the end user.

The thing about S30V is that it has been around a long time, is well understood so you can feel confident that people know how to properly heat treat it. S30V seems to loose a fine edge quickly, then keep an excellent working edge forever.

Super Steels

Here we have S110V, S90V, M390, M4, CTS204P and others. Be the first on your block to collect them all!

Note that the numbers in the S-series indicate the percentage of vanadium. S30V has 3 percent. S90V has 9 percent. S110V has only 9 percent though.

Also note that S30V is tougher and easier to sharpen (but not easy) than S90V or S110V. What you get with S110V is superior edge holding. The concensus seems to be that S110V is a tiny bit better than S90V.

X50CrMo14

I have some kitchen knives by Wusthof and am told that they use X50CrMo14 at 56 HRC. X50CrMo14 is very similar to 425M. Note tha 425M is similar to 440A and in the above list would barely make it to the "OK steel" category. So this is an easy to sharpen stainless steel that will need frequent sharpening, but take a good edge. It is not in the same class as the pocket knife steels being discussed above. Buck used to use 425M in its knives, then moved up to 440C and 440HC.

Note also that many pocket knives get hardened to 60 HRC or so.


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Tom's Knife Info / tom@mmto.org