RC Hardness us vs them thread. Let's talk about the rumors

[jtoler_9]

I am still new to knives and over the past few months I have done the BST with a few of my favorite vendors. There's a lot of hype out there when comparing knife vendors. One common dispute I run into is RC hardness. For example. Vendor S does better heat treat than vendor B therefore an M4 blade with Vendor S is superior. Or Vendor S runs their M390 steel harder than vendor B so it's better. What I haven't been able to find is where these data points are coming from. I have NO way to test RC hardness in my home, nor do I know anyone who would know how to do it. Are these rumors accurate? Most vendors give a range of where the RC hardness will fall, since production knives are never going to get it at 62RC every time. So it stands to reason that if I had 1 knife from Vendor B and 1 from vendor S and I just happen to get one at the high end of one and the low end of the other, then my data would be specific to that test group. But I don't think that is enough data to make a definitive claim that vendor S Runs their M390 or M4 steel harder than vendor B every time.
So cutting out all the hype, is there truth in these rumors? Is there any test data to corroborate these findings? Is there a knife manufacturer that reigns supreme in RC hardness? Or is it all BS? All feedback welcome here. I am trying to learn.

 

[unit]

Wow, there must be something in the air today.

I would suggest that not everyone agrees on ideal hardness for some steels (both knife users and knife makers). Compound that with the concept that some knives are designed and built with different purposes in mind that might warrant different desired hardness. (for example a large fixed blade might be run a bit softer than a small folder for some obvious reasons)

I would further suggest that some companies have been known to change their target hardness for some steels based on various factors. (for example, a company runs a steel very hard and numerous complaints roll in from users that chipped or broke the blade, so they back off on hardness...much to the disappointment of a handful of enthusiasts...depending on which user you are, which hardness is supreme?).

I would also suggest that there are a lot of people out there "testing" knives and associating differences in performance with steels and or hardness of the steels while ignoring glaring differences in blade geometry.

Short answer...be careful with rumors.

 

[jtoler_9]

Short answer...be careful with rumors.

Thanks for the post. There is definitely more to it than I yet know. I think your short answer is perfect.

 

[Ankerson]

Wow, there must be something in the air today.

I would suggest that not everyone agrees on ideal hardness for some steels (both knife users and knife makers). Compound that with the concept that some knives are designed and built with different purposes in mind that might warrant different desired hardness. (for example a large fixed blade might be run a bit softer than a small folder for some obvious reasons)

I would further suggest that some companies have been known to change their target hardness for some steels based on various factors. (for example, a company runs a steel very hard and numerous complaints roll in from users that chipped or broke the blade, so they back off on hardness...much to the disappointment of a handful of enthusiasts...depending on which user you are, which hardness is supreme?).

I would also suggest that there are a lot of people out there "testing" knives and associating differences in performance with steels and or hardness of the steels while ignoring glaring differences in blade geometry.

Short answer...be careful with rumors.

Yep, so true.


Also there are so many idiots out there the makers have to back off on the HRC hardness somewhat so that's why we normally see blades that are below optimal hardness 1 or 2 points and or thick blade geometry around .025" -.030" plus behind the edge.

They just don't know what all the joe six packs or keyboard commandos will do so the have to go by averages....

 

[michaelm466]

From my experience, you want super steels (super in the edge holding category) to run harder to get the most out of them, this does make them lose some toughness depending on what particular steel you're talking about, in general in my experience, Company S, generally runs (now ran) say CPM-M4 about 2 points harder than Company B and there is a perceptible difference, however as of this year company B has bumped up their hardness range on M4 (62-64 instead of 60-62) at least and I think M390 as well, to match company S's hardness range, therefor as of this year, both should perform equally. IMO, if you're going for a super edge retention steel you want it specifically for edge retention, therefor you want the highest hardness the steel can support, not to sacrifice some edge retention for toughness or ease of sharpening, if you wanted that you'd go for a good all arounder like S30V, 154Cm, VG-10, etc

For steels that are more all-arounders like say S30V (good at most things, not great at anything) you can run it harder for better edge retention sacrificing ease of sharpening and some toughness, or run it softer for ease of sharpening and better toughness at the sacrifice of edge retention and their is a spot for both of these in the knives depending on what the knife intended uses are.

Anyway bottom line, that was true in the past (RC numbers came from each companies websites) however they're now running the same target hardness for their super steels so they should be pretty much equal.

 

[Ankerson]

Anyway bottom line, that was true in the past (RC numbers came from each companies websites) however they're now running the same target hardness for their super steels so they should be pretty much equal.

Nobody knows unless they have the blades tested......

Production heat treating is done on an average range, usually + or - 2 points so the real numbers can vary some between blades and batches.

 

[michaelm466]

Nobody knows unless they have the blades tested......

Production heat treating is done on an average range, usually + or - 2 points so the real numbers can vary some between blades and batches.

Well yes, they're both going for the average range of 62-64, but each blade will probably differ, but at least its not 60-62 for one and 62-64 for the other.

 

[Tsujigiri]

I think I know what the "S" and "B" stand for...

Another factor people who make these claims might be missing is that "S" tends to have much thinner grinds on their knives as "B." So a typical knife from "S" will seem sharp even after it's gotten dull, because the grind is more conducive for slicing.

 

[Ankerson]

Well yes, they're both going for the average range of 62-64, but each blade will probably differ, but at least its not 60-62 for one and 62-64 for the other.

The problem with your theory is that blades from either range could come in at 61-63 in actual testing given the variables....

Rockwell testing is in general + or - 1 RC so 62-64 could in fact be 61-65 and 60-62 could be 59-63 so there is some overlap.

So in the end it depends on what they are shooting for and how tight they really want the RC range to be, that's why the ones who do post the RC data give a range.

The maker however depending on who is doing the heat treating and how good their furnace is can get them to hold the tolerances to + or - 1 RC so that would narrow down the variables somewhat.

That's if they don't overload the furnace to save money or aren't HTing more than one grade of steel at a time........

Lots of things can happen so I wouldn't take those numbers too seriously most of the time.

That's not even getting into how steels can change from batch to batch and those variables involved.

Not all makers can take on 10,000 LBS of one steel at one time.

 

[knarfeng]

I am still new to knives and over the past few months I have done the BST with a few of my favorite vendors. There's a lot of hype out there when comparing knife vendors. One common dispute I run into is RC hardness. For example. Vendor S does better heat treat than vendor B therefore an M4 blade with Vendor S is superior. Or Vendor S runs their M390 steel harder than vendor B so it's better. What I haven't been able to find is where these data points are coming from. I have NO way to test RC hardness in my home, nor do I know anyone who would know how to do it. Are these rumors accurate? Most vendors give a range of where the RC hardness will fall, since production knives are never going to get it at 62RC every time. So it stands to reason that if I had 1 knife from Vendor B and 1 from vendor S and I just happen to get one at the high end of one and the low end of the other, then my data would be specific to that test group. But I don't think that is enough data to make a definitive claim that vendor S Runs their M390 or M4 steel harder than vendor B every time.
So cutting out all the hype, is there truth in these rumors? Is there any test data to corroborate these findings? Is there a knife manufacturer that reigns supreme in RC hardness? Or is it all BS? All feedback welcome here. I am trying to learn.

I have access to a Rockwell tester and have tested the hardness of many of my knives.
*Jim Ankerson is right that, when comparing the results of two Rockwell testers, the results cannot be compared beyond ±1, because that is how accurate the calibration standards are. The machines themselves will measure to a fraction of a point. But machines calibrated to two different official standards are only good to ±1.

From my tests I have reached some conclusions.
1) Not all companies heat treat the same alloy to the same hardness. The hardnesses were far enough apart that they could not have been the same. You can even see that in the published hardness specs that some of the companies publish. I have seen specs showing AUS 8 as hardened to a 56-58 and others showing a 58-60. Jim Ankerson and Unit did an excellent job of explaining the reasons why knife companies sometimes choose a lesser hardness range for their blades.

2) I have never measured a blade hardness and found it to be outside the published spec of a manufacturer. Not all manufacturers publish their hardness specs, but I have found the specs which were published to be accurate.

 

[hardheart]

I have taken it to mean that the target hardness for the heat treat is, for this example, 63, and that the range is advertised so the different machines will still measure within the ±1 range. Knives are pretty small pieces of steel that change temperature quickly and do not vary from surface to center a great deal, one would hope hardnesses would not vary a great deal. A quarter inch is fairly thick for a knife, while foundry recommendations for heat treat give soak time changes per inch of difference.

 

[spydusse]

Benchmade is running their m4 harder this year to match spydercos. That should answer your question. They even had blade put the m4 s hardness of a new blade in the knifes decription in last months issue

 

[JNewell]

Short answer...be careful with rumors.

I'd further add: be careful with facts. Jim's testing thread shows that primary and secondary grinds can influence performance, at least under a specific test protocol. And, I'd bet that using a different test protocol, Jim's results might come out differently. In short, there are a lot of facts that, if changed, can change test results. Your cutting needs may not mesh well with the way even a well-controlled test is being conducted!

Personally, it's easy to get excited about the differences that show up in testing like Jim's, but in real life (as I've said before), anything from properly hardened ATS-34 on up is a great blade from my perspective (YMMV). :thumbup:

 

[Ankerson]

I'd further add: be careful with facts. Jim's testing thread shows that primary and secondary grinds can influence performance, at least under a specific test protocol. And, I'd bet that using a different test protocol, Jim's results might come out differently. In short, there are a lot of facts that, if changed, can change test results. Your cutting needs may not mesh well with the way even a well-controlled test is being conducted!

Personally, it's easy to get excited about the differences that show up in testing like Jim's, but in real life (as I've said before), anything from properly hardened ATS-34 on up is a great blade from my perspective (YMMV). :thumbup:

Not really because I have very strict criteria that the blades have to meet or they just aren't tested to start with to cut down on the variables as much as I could.

While not perfect as it's done by hand it's very accurate and the results are repeatable.

 

[JNewell]

Jim - was thinking, for example, of the different S90V results (Military and Paramilitary 2 vs. Manix 2) and M390 results (Spyderco Mule vs. Benchmade 710). I may be misinterpreting the significance of the differences, though.

 

[Ankerson]

Jim - was thinking, for example, of the different S90V results (Military and Paramilitary 2 vs. Manix 2) and M390 results (Spyderco Mule vs. Benchmade 710). I may be misinterpreting the significance of the differences, though.

They were different hardness, the Military and Para 2 at 60 and the Manix at 59, the M390 BM was at 60 and the Mule was at 60.5.