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azraelsblade
72
Jun 15, 2017
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Anyone know how hard they are running the S35VN? I'm a bit frustrated with so many production knife companies running it soft (58-59) compared with how well it could perform at a higher Rockwell-C (60-61).
Jun 15, 2017
Epic_Enkidu
197
Jun 15, 2017
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Legitimate question, what kind of an impact would a differnce of one or two ponts make?
Jun 15, 2017
Bobraz
1699
Jun 15, 2017
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Is really 1 point less (say, 59 instead of 60) that much difference in reality? Is this a non-linear scale?
As for me, I'm more a collector than an EDC'er, so I don't really care. I just carry a small Pingo with custom carbon fiber scales. Anything else and people are really afraid. I'm in Canada.
Jun 15, 2017
azraelsblade
72
Jun 15, 2017
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Rockwell-C is a log scale so "one or two points" would actually represent an exponential increase in hardness. Thus is could have a relatively profound impact on edge retention, wear resistance, toughness. CRK used to run their S35VN at 58-59 and more than a few people complained about it being too soft and with recent batches they have run it harder at 59-60 with arguably better edge retention. Most custom knife makers (eg: Rick Hinderer, Jim Skelton) run their S35VN at around 61 HRc and this is where the steel really shines for what most people would use their EDC knife on (paper, cardboard).
Jun 15, 2017
azraelsblade
72
Jun 15, 2017
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AAAANNNNDDDD Eliot just replied to my IG message about it. 61 HRc confirmed! WOOT! I'm in like Flynn.
Jun 15, 2017
Epic_Enkidu
197
Jun 15, 2017
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Thanks for the reply! The knife world seems to be a lot more technical than I thought :P
Jun 15, 2017
WE runs S35VN at 60-61 RHc and your question is vastly more complicated to me than most people would. Bear with me on this one, it will circle back to your question after I lay some groundwork. When it comes to martensitic steels there are tens of thousand of different alloys, some specifically made to have specific characteristics for specific requirements, others are more generalized and can do lots of jobs. Knives have a rather peculiar set of operating conditions and within the category of knives, pocket knives have one of the broadest set of operational demands at this point in the history of knives. The general consensus is we want pocket knives that are easy to sharpen, but stay sharp for a long time, don't rust in our pockets, and are durable enough to endure misuse (filling in as a screwdrivers or prybars) from time to time. The problem is those desires are, for the most part, inversely related to each other when it comes to high carbon stainless steels. One of my favorite completely made up term (it has no real standardized test, CATRA is not a standardized test) is "edge retention". "Edge retention" gets really really tricky to define when you look closer at what it actually means and the variables it brings into question. The initial supposition would be that it is measure of how long the edge is retained, but there is no quantification of start point or end point in that duration, so ascribing a duration without a beginning or ending parameter makes the term inherently nebulous and indefinable. However for the sake argument let create a start point called "sharp" and claim that "sharp" cuts an ASTM standardized material like PVC tape (electrical tape, the black kind) with 1 joule of force (fairly small amount of force) with the edge of the blade perpendicular to the tape (push cut). Let's say that, and this is all completely hypothetical, our blade will cut the tape 300 time with the same force on the same material before is doesn't cut the material with the same amount of force in the same vector. Now we have end point we can call "not sharp". Now we can ask the question "why did it stop cutting". The answer is wear for this particular test. PVC, like most plastics is fairly abrasive and adhesive (nothing to do with the stickiness of the tape), so we can assume there is abrasive and adhesive wear, meaning as our two materials are interacting with each other molecular bonds are being broken on both materials through the two main vehicles of wear. I find adhesive wear to be tough to explain with any kind of brevity so I will quote the least complex definition I have found: "Adhesive wear is caused by relative motion, "direct contact" and plastic deformation which create wear debris and material transfer from one surface to another. " It's a tricky thing to explain, but it is a component of the wear our blade is experiencing. In short the tape has less wear resistance than the steel in the blade so it's bonds get broken more, but there is still molecular loss on the blade too so over time it loses material at its apex and eventually can no longer cut because the apex is now rounded off. Now there are standardized tests for wear resistance, there are quite a few, ASTM and STLE have the most widely used tests. But they produce conditional results, things that require an understanding wear testing and what the test is actually testing for since they are set up as X vs Y (material in question vs a standard test implement martial, in short it's not a very sexy, easy to compare set of results even though wear is the most common "dulling" agent. The next most common reason for loss of cutting ability is deformation, either a rolling of the apex or micro-chipping along the apex. This "dulling"agent is not accounted for in our PVC cutting test because we were using small and constant force in one vector, but in the real world knives encounter large and variable forces in all axises of motions. There are a few standardized tests the can give us insight the performance of a steel, but just like in the wear resistance example they are not particularly attractive or succinct numbers that grant us the ability to cross-compare very well unless you do this stuff for a living and a lot of time converting units like Mpa and joules into things like ft/lbs and then run then through equations to get an idea what the number means in the real world. For example I often ask about the flexural strength of a steel with a specific heat treatment in a specific cross sectional thickness so I can have idea how much someone can pry with the tip of a blade before it snaps off. Similarly I am concerned with impact resistance, not because I expect people are going to be chopping with their folding knife, but because I make flippers and the blade will be slamming into the stop pin of the knife with frequency and over long periods of time. I also ask this question of the stop pin material. Deformation is a major engineering concern and is, in my mind, a vastly more important measure of a blade steel's performance than any specific wear resistance characteristic. But while I have been discussing them as independent variables, they are not. Wear resistance and resistance to deformation are correlated, however the type of deformation resistance (primarily elastic and plastic) have inversely correlated relationship in high carbon steel most of the time. This is not a concrete rule though because there are enough instances where certain heat treatments can yield contrary correlations that i can't be definitive. If I haven't lost you yet, this is where we can start to talk about the hardness and the Rockwell C scale in particular. I needed to explain a little bit about wear resistance and deformation resistance so I can present a clearer picture of what Rockwell hardnesses actually mean and what we can infer from them. For high-carbide forming martensitic stainless steels (that amount of specificity is important for this claim), the general rule for Rockwell C hardness goes that the higher the number the less sharpening your knife will require over it's life span, at least that's what most people think it means. Just like most things in life the deeper you look the more you find this is not really the case. The Rockwell series of test press a diamond tipped probe in the test material, the divot left by the probe is then measured and a value can be ascribed based on the depth of the divot. For the C scale a diamond tipped 120 degree spheroconical probe is used at 150 Kgf (kilogram-force, it's the force of 1 Kg under the force of gravity, what we call the weight of a 1 Kg mass) of force. This is the equivalent of a 330 lbs weight. So what this test actually test is amount of plastic deformation (permanent movement of material). What we can say for certain based on a Rockwell C test number is that the test piece resist a 330lbs focused force to a level according to its test number, that is all. There are things we can infer from that number, since there are some demonstrable correlations. We know that the higher the Rockwell number the higher the tensile strength of the material. Tensile strength is a pretty useless thing to know in a knife since knife blades are almost never being pulled along the same axis and this in not in the operational paradigm of a knife. However we can infer a level of correlation (less significant than the correlation between Rockwell hardness and tensile) between tensile and flexural strength, or lateral yield strength or any test that seeks to ascertain how much force can be applied to our blade before it; bends and returns, bends and stays bent, bends and breaks. We can say with a reasonable degree of certainty that high-carbide martensitic stainless steels require less lateral force to break the higher their Rockwell C test number. This means that the higher the RHc the greater the chance for chipping and breaking, but the lower the chance for rolling the edge. The other corollary of hardness is wear resistance and at the particulate level the harder something is the less it will wear, but high alloy steels have very complex particulate make ups and structures and in some cases the sum of the parts can be greater than the whole. It is this very thing that high-carbide martensitic stainless steels are trying to achieve. This is the magic of steel at it's most basic level. We take iron and carbon, one soft and ductile, the other so hard it's usually crumbly powder and we put them together to form an alloy that can have a balance of the two major properties. Lest I start slipping into the intricacies of modern metallurgy and effect of alloy elements, let's circle back to the difference between 58-59 and 60-61 RHc. Given what I have explained above, and it's just a gloss, the highest tip of the iceberg, I hope you can see that at the base level the answer can be "not much" in one sense and "worlds apart" in another, depending on how close you are looking at the question. Published data for S35VN that concerns itself with test data that I look for with regard to heat treatment and thus end RHc values is rather sparse, often is for steels that are not used in larger industries like Aerospace and Plastics (these are the 2 industries that specialty stainless steel are normally designed for, they just happen to work well in knives too). Having sharpened and used S35VN at 58-59 and 60-61 I can say that the harder S35VN does stay sharper longer performing the cutting tasks (which are fairly consistent over time for me) that I use a knife for regularly. Now I am completely jaded and biased when it comes to sharpening so I find them both easy to sharpen (steels like S125V falls under the category of hard to sharpen for me). I will issue a very big HOWEVER at this point. The correlation between RHc and tensile strength is a linear correlation, but the correlation between tensile and flexural is not and it is nowhere close to one to one. This means that there is an unknown decrease in the amount of force it would take to chip an edge, but my educated estimate is that we are gaining, at the very minimum, an increase in resistance to edge rolling and the noticeable increase in wear resistance I see in an anecdotal way. I don't know if the causal knife user would notice any difference however. I hope that wasn't too confusing.
Jun 15, 2017
eksuen
704
Jun 15, 2017
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Thank you for the detailed response. That was very informative.
Jun 15, 2017
Gunmonkey1974
78
Jun 16, 2017
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I just talked about this in a video this morning... I know that WE runs thwit S35VN a good bit harder that CRK but I don't know exactly what Rockwell ... I would imagine you can look it up because they make most if not all of their knives out of that steel
Jun 16, 2017
rantng
702
Jun 16, 2017
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Is that a record for the longest ever single post in the discussions? :-) Much appreciated
Jun 16, 2017
Gunmonkey1974
78
Jun 16, 2017
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Yeah ... what Elliot said...
Jun 16, 2017
namhod
1980
Jun 16, 2017
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@FerrumForgeKnifeWorks
First I would like to say.
Neeeerrrrdddddd. You're a f***in nerd, and no one likes you.
No but seriously, I am buying the knife now. My wife will be upset if she finds out. Merry Christmas to me.
Thanks.
P.S. if you dont get the joke, watch hot tub time machine.
P.P.S. If you don't get the joke you suck.
Jun 16, 2017
chaosmagnet
68
Jun 16, 2017
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Great explanation, thank you!
Jun 16, 2017
Bflying
1038
Jun 16, 2017
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FFKW, wow, that was a great read. Thank you for taking the time.
Jun 16, 2017
azraelsblade
72
Jun 17, 2017
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This is why you are one of my favorite people in the knife industry.
Jun 17, 2017
hi808dave
9
Jun 24, 2018
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Wow, I genuinely appreciate your time to provide such a detailed explanation on the topic. Thanks again.
Jun 24, 2018
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