Why HRC Matters...and Why It Doesn't

Added: 2026-05-25

[00:00:00]What's going on, guys? Uh, back with another video today. This is kind of an impromptu video. Um, it was based off, uh, actually what made me think about it was this knife right here. Uh, the topic of today's video is going to be why HRC matters and why it actually really doesn't sometimes. Um, there's been a lot of talk lately about HRC. again with all the results from the hardness testing. Uh the website steel hardness lab or if you follow him on Instagram, Taylor Hardness, he does a lot of hardness testing. Um I think he's up to like four or 500 different knives tested at this point and the results get shared on Facebook groups, Instagram, that kind of stuff. So uh it generates a lot of discussion and uh I think it's a good thing to talk about. Again, I was part of a movement, if you want to call it that, uh, some years back, pushing for higher hardnesses, and I think overall it was a good thing. Uh, we see more companies now pushing the envelope with seals and hardnesses than we ever did before. Uh, Spyderco's always been good at it. Um, but there's all sorts of them now. Kershaw is doing a pretty good job.

[00:01:04]Benchmade does a decent job on some steels. Uh, a lot of the companies now are pushing higher hardnesses and you're now seeing more companies willingly disclosing what they're running uh, their knives at, which is cool. That wasn't a thing, you know, seven, eight years ago and and now you're it's more easily found. Overall, I think that is a net positive for the consumer. It's always good to know exactly what you're buying. Um, I think that is just a overall good thing in the market. If you guys have been around for long enough, you know I've always been a proponent of high hardness steels. Um, Maximit, Rex121, K390, um, all that kind of stuff. Uh, but as my knowledge has grown on this topic, my opinions on some things have changed on this. Now, I think it goes without saying that hardness is not the end all beall of knife performance. Um, case in point is this knife right here. This is Rex 76. and edge retention on it isn't like absurdly outstanding compared to stuff like Maxim or or Rex 121. And this is just as hard as those seals are. This is like 68 69 HRC.

[00:02:17]So obviously hardness isn't everything.

[00:02:20]Um steel and heat treating is incredibly nuanced and you can follow that rabbit hole forever. You can literally research this for years and years and years and that's why there's a whole profession about it. uh there's always new stuff being uncovered in this in this field.

[00:02:36]Now, assuming all other variables are equal, I believe that the three factors that control abrasive wear resistance, which is what most of us encounter on a day-to-day basis, you know, cutting cardboard, opening packages, uh that kind of stuff, the three factors I believe that control that type of wear resistance the most are hardness, carbide volume, and carbide type in that order. There are sacrifices to higher hardness though. Uh we all know that higher hardness leads to lower toughness um which is your resistance to lateral stress which is why you see uh maximate you see if you're part of Facebook groups and stuff you see these broken on a semi-regular basis because people use them for stuff that they're just not supposed to and they break. Um this is a very high hardness steel, high carbide steel and it just doesn't do good with those stresses. With that being said, higher hardness though does lead to an increase in edge strength. Um, which is your resistance to edge deformation. So, the mode of it doulling is just going to be the flattening of the apex instead of any chipping or rolling. The other sacrifice that isn't quite as obvious is the carbide volume. Higher hardnesses require higher oenetizing temperatures, uh, which is the temperature the steel is soaked at during heat treat. And there's an inverse relationship with oenetizing temperatures and the amount of carbide in the steel. The higher the oenetizing temperature is, it leads to more carbide being dissolved into solution, which means there's less available to help in wear resistance.

[00:04:05]Um, steel actually has the most carbide volume in its annealed state like this, just in a bar. This bar of S125V has the most carbide it's going to have right now in this state. as it gets heated up, it loses more and more and more and you have less carbide volume. This is why whenever you see a microraph of a steel uh that shows the carbides and an osatizing temperature is listed below it normally um since the volume varies quite a bit based on what temperature it was heat treated at. Now we know that fine grain structure is preferable for better toughness, edge stability, sharpening and other qualities. Um the carbides actually help in that too.

[00:04:44]Carbides help pin grain boundaries so they can't grow. So, if too much carbide gets dissolved into the steel, excessive grain growth can occur, which leads to inferior uh properties. It's going to have lower toughness. It's not going to sharpen nearly as well. The edge isn't going to come up as crisp. And in this case, the hardness may even be the same or higher. So, a hardness test isn't going to show that. So, I think that goes to say, I think there's a balance to be struck between the properties. Uh the highest possible hardness may not be the best in all scenarios. You want the best balance of carbide volume and hardness to support those carbides properly in the steel matrix. Now, there is kind of there's two examples I have here. Um, number one, I think is a steel like this. This is uh 8670. Uh, this is just a plain carbon steel. Really about as basic as you can get. On Lens charts, it is the lowest edge retention steel.

[00:05:35]Um, but that's because it's run at a low hardness. It really doesn't have super high attainable hardness, but it also has super low carbide volume. And the carbide type is just cementite, which is just iron carbide. It's the softest car.

[00:05:49]It's the softest carbide type there is.

[00:05:52]So, in this case, the carbides may not be crazy important. If you run this at a higher hardness, like this is 63 HRC, you're going to get better edge retention out of it. Now, I think the best example of this though, uh, is this knife or this steel right here. It's 15V.

[00:06:09]This can touch 69 HRC, but all the Spyderco stuff that we've seen tested, which has actually been quite a few has been testing between 64 to 66 and a half. Uh, if you just looked at the data sheet and saw 69, you' think that Spyderco is running these super soft.

[00:06:25]But because Shawn wanted these run at a certain hardness to get the properties that he wanted, I've never heard anyone complain that this steel doesn't perform phenomenally. This is literally, I think, the best steel in the market at this point. That's not to say that hardness isn't still an incredibly important metric, though. Looking at Laren's edge retention chart, the overall trend is harder steels just cut for longer. Uh, it goes from the bottom left all the way up to the top right, the harder the steel gets, generally the more that it cuts. That metric is also the most easily measured. Hardness testers are far more common and cheaper than the microscopes that it takes to see steel microructure and carbide volume. So, while hardness doesn't tell the whole story, I think it's a great indicator of edge retention. Overall, I think the hardness testing that's going on right now is great. Uh, I think it's building a great database of steels and the hardnesses for them. Just like the 15B here, we've got like I think it's 20 20ish tests on it now. So, you kind of get a good range of what Spyderco's been running them at. Uh it's kind of fun to look at and compare certain steels and see what they're run at across the industry based on company and all that.

[00:07:34]Uh but the big picture is a little bit more complex than who's running what at higher HRC's.

[00:07:39]What it is great for is seeing what companies are delivering on the hardnesses that they advertise. I think now more than ever, it's important that people are getting what they are spending their hard-earned money on.

[00:07:50]Money's tight, so you want to know that you're getting the performance that you're paying for. And testing like this is a good way to hold companies accountable to hitting their marks. With all that being said, I think that's going to do it for today's video. If you guys enjoyed the video, drop a like down below and subscribe if you aren't already. Thanks so much for watching.

[00:08:06]Have a great day.