General Hardness of Blades

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Less Than Sharpest

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I was thinking that I shouldn't even say anything as I'm new to posting and I didn't want to upset anyone on here, being that there are a lot of collectors, but this morning I thought differently. I'm not trying to hurt anyone's feelings, but there does seem to be a problem with manufacturers posting the hardness of a steel they use on a knife and the actual hardness that a given knife can be measured at. First, I was a knife sharpener for many years and was able to handle many different types of steel and was always amazed by the rare example of a blade that was perfectly hardened. Some steels were beyond all reasoning when it came to this somewhat non-scientific approach, but just imagine that I sharpened well over 100,000 knives and I always paid attention to what I was doing.
Secondly I personally made about 60 knives myself, all in ATS-34, and every one of them was Rockwell tested by myself to make sure that they were at the stated hardness which was 61 on the C scale. Also I want to say that I'm not a scientist and my overall methods were somewhat less that scientific, but I think that applies to most of us.
I have a few knives in ZDP-189, and they are all of San Mai construction, that is there's a softer steel on either side of the cutting steel, so I don't know how a company would measure the actual hardness of the edge. But I can tell you that the person sharpening can tell you right away. Many years ago there was a particular manufactured knife that was very much in demand and I discovered that there were some that were not hardened at all! They were all about 45-50 Rockwell and I had to argue with some people to not ship those blades. When we would get a shipment of blades back from the heat treater we would pull a few off and measure them, and there was quite a variety when it came down to what we would measure. But I can tell you all that very few blades were ever cast aside because they weren't up to par hardness wise. That is manufacturing. That is the real world.
So now there's some discussion about the merits of M390 vs 20CV and what it all means in term of edge retention. I can say for certain that it means everything. An ATS-34 blade that is actually 61 Rockwell will out cut a 20CV blade that is only 58. And I own some blades that are not as hard as they should be. When I watch a video of someone performing a cutting test, that is with two knives if the same steel, first I admire them for trying, but are they really comparing an apple to another apple?
I'm not an expert, and I welcome your responses. Please let me know what you think. I have carried a couple of different blades in M390, and a couple in 204P and I have some opinions on which steel is better.
Thanks for reading.
dt
 
Hi, there was a big fuss here a while ago about "oh noes these knives are too soft" from few new users were obsessed with hardness.

It tuned out they weren't performing the test accurately and they had to walk back their comments, apologize and then they packed up and left never to be seen again.

They pretty well all noted themselves as expert users too.

You'll have to note that this isn't meant to upset you but no human can accurately verify hardness by hand or eye. Regardless of experience. Sure you can hit it with a file Forged in Fire style but that just makes for good TV; not for accuracy.

The manufactures test the knives in batches and there is an acceptable range for the batch. That's good enough for me.
 
Danke42,

No hurt feelings here. Perhaps you didn't read my whole post; I wrote, "I'm not an expert."
I think that many of us tend to forget that this is one place where ordinary people can come together and post ideas or opinions, and that's what makes it interesting for most people. For the record, I have sharpened far, far more than 100,000 knives over the years, and that one can verify relative hardness by the way that something feels. When you do it over and over again, you can honestly tell if something isn't right. This is something that we as humans have turned our backs on. I worked for a major knife manufacturer and I've sat down at the Rockwell scale quite a few times, and I know that there are acceptable limits for hardness. Regardless of experience.

So thanks.
 
For a fact, I know that some knives do not rockwell at the reported ranges...stuff happens. I'm willing to believe that in the great majority of such cases, it is an accident and not an intentional oversight.

But what is the main takeaway you are offering us for consideration? Most of us are not going to have our blades rockwelled, nor are most testing the hardness of various steels with files the way it used to be done.

So, do you have a suggestion or are you just getting this off your chest? Your points are valid, I'm just trying to understand the action plan you have in mind.

ETA: I have had occasion to return a knife or two, (custom knives), to makers who agreed with me upon receipt of the knives that there must have been a failure during the heat treat for the issues I reported, and they verified, to have occurred.
They also remedied the situation. But these were standup, reputable custom makers.
 
Blues,

I really didn't have an action plan in mind, I was just stating for the record of sorts that there's a lot of emphasis put on what we are told by manufacturers with regard to specific steels, and I've noticed that some people want to argue the point just because they feel they're correct when the whole issue is a very grey area. My main point is that we should take the time to realize that most knife companies don't always ship what it is they're selling. And it's not intentional, it's not like a company sets out to deceive their customers (okay, some do), but stuff happens. I just don't think that most people realize what happens in manufacturing. Or to be more specific, knife manufacturing.

I have over the years read of some people who want to argue their point when they should just enjoy the hobby and realize that it's not a hard science. If there's a problem with a certain knife then by all means contact whoever produced it and let them know. But don't bad mouth a specific maker or company if their product doesn't match what you had in mind without giving them a chance to make up for their shortfall. Of course, if you run into to same problem over and over then it's probably not something that they're willing to correct.

Fair enough?
 
I think the HRC of laminated blades is a guess based on expected hardness, because if you quench and temper at computer controlled temps you can kind of reliably predict the outcome of the hardness (Or should be able to predict it to a rough degree of 1-2 points) I understand what you are saying though, because laminated blades usually dont have hard unjacketed steel on the flat riccaso, and you need a perfectly flat portion of the blade to put in a HRC indentation machine, you cannot put the angled bevel portion in those machines. But you can actually get high tech computer HRC testing devices (Don't know if knife companies use them) So it is technically possible to get chemical composition and hardness readings by using other devices than HRC indentation machines.
I have a set of Japanese hardness testing files but they only give HRC results in intervals of 5. So 40-45-50-55-60-65 and so on, so I can tell if a blade I make is above 60 and below 65, but I cannot tell if it is exactly 64 for example. But I can tell if it's closer to 65 or closer to 60 depending on the level of bite each HRC testing file gives. Even with basic heat treating equipment (Not using a computer controlled evenheat oven) I can reliably estimate the hardness to a certain degree of some 1095, by water quenching, and then tempering at 200 degrees, I know roughly what HRC it will be at, and I know roughly what HRC it will come out if I temper higher at 220 degrees.
Some companies batch test (Not sure about laminated blades those are probably educated guesses) Some companies do individual testing though for each knife, like for example Rockstead are known to individually test each knife, I'm not sure about William Henry, but they do stamp the blades hardness on each knife as well, maybe they do small batch testing, but I know Rockstead do test every knife. Lots of custom makers test every single knife as well, like Big Brown Bear, I see shawn testing every one of his knives after he makes them.
 
Londinium Armoury said:
Lots of custom makers test every single knife as well, like Big Brown Bear, I see shawn testing every one of his knives after he makes them.
Click to expand...

Shawn, @DeadboxHero has the passion. I had a long phone conversation with him the other night and I felt like I was at a revival meeting. :p

The man's got it bad. And that's good for the rest of us. :cool:
 
My main concern with hardness is the difficulty in sharpening. I don't mind sharpening but don't want to take longer than the cutting task to do it. I'm a fan of traditional steels. 52100 and 1095 particularly.
 
kvaughn said:
My main concern with hardness is the difficulty in sharpening. I don't mind sharpening but don't want to take longer than the cutting task to do it. I'm a fan of traditional steels. 52100 and 1095 particularly.
Click to expand...
Have you used diamond stones? Not only will they sharpen high carbide % knives quickly but you can even reprofile or thin a knife relatively easily. I'm talking steels like s110v, zdp189 and other of the sort.

Op:. I am not sure what you want the people testing the knives to do, as most people don't have access to a machine to truly test hardness before doing a cut test. Also seems like you sell your self a bit short, if you made almost 60 knives you must have a pretty good understanding of heat treatment and hardness .
 
Blues said:
Shawn, @DeadboxHero has the passion. I had a long phone conversation with him the other night and I felt like I was at a revival meeting. :p

The man's got it bad. And that's good for the rest of us. :cool:
Click to expand...

He does have a passion and a lot of knowledge about heat treating and getting the most out of steels. I've exchanged quite a lot of messages with him, he has taught me a lot about blade steels. Even when I was a difficult and annoying person to teach, he had the patience and drive to make sure he drilled certain lessons into my head. He knows his stuff.
 
I just spent about a half hour working up a Cold Steel Bush Ranger in S35vn on my KME using DMT stones up to 600. It takes some patience for sure.

I was sorta bummed I had to even do it. The edge has crumbled into serrations after using it on some single wall cardboard.

This is partially why I get more enjoyment out of softer steels. I prefer a quick tune up on an edge that won’t fall apart when contacted on abrasive material.

I do however like using high wear, high hardness steels when they are sharpened correctly and that don’t have over-heated bevels. It seems like many of my production blades have this issue.
 
MolokaiRider said:
I just spent about a half hour working up a Cold Steel Bush Ranger in S35vn on my KME using DMT stones up to 600. It takes some patience for sure.

I was sorta bummed I had to even do it. The edge has crumbled into serrations after using it on some single wall cardboard.

This is partially why I get more enjoyment out of softer steels. I prefer a quick tune up on an edge that won’t fall apart when contacted on abrasive material.

I do however like using high wear, high hardness steels when they are sharpened correctly and that don’t have over-heated bevels. It seems like many of my production blades have this issue.
Click to expand...

It's most likely due to the vanadium content and other hard carbides in high wear steels. They tend to resist grinding wheels and belts more in the factory, which leads to them spending a longer time in contact with the belt leading to over heating. Where as simple steels tend to grind faster and only take a few quick runs along the contact wheel or belt to put a bevel on them.
I don't know why so many dry grind, they have high tech factory workshops and can easily set up water jets or coolants to keep the blade cool while grinding.
I mean even in my back garden with my cheap rookie set up I just aim a garden hose on spray setting at my grinder, belt or wheel, it even works for using a high RPM angle grinder which gets very hot fast and I never burn any of my edges. I keep a bucket of water on hand to dip the blade in after every 1-2 runs. They could easily eliminate burnt edges if they just made a coolant spray set up, I mean I do it with a £10 hose and some cheap clamps.
 
Londinium Armoury said:
I think the HRC of laminated blades is a guess based on expected hardness, because if you quench and temper at computer controlled temps you can kind of reliably predict the outcome of the hardness (Or should be able to predict it to a rough degree of 1-2 points) I understand what you are saying though, because laminated blades usually dont have hard unjacketed steel on the flat riccaso, and you need a perfectly flat portion of the blade to put in a HRC indentation machine, you cannot put the angled bevel portion in those machines. But you can actually get high tech computer HRC testing devices (Don't know if knife companies use them) So it is technically possible to get chemical composition and hardness readings by using other devices than HRC indentation machines.
I have a set of Japanese hardness testing files but they only give HRC results in intervals of 5. So 40-45-50-55-60-65 and so on, so I can tell if a blade I make is above 60 and below 65, but I cannot tell if it is exactly 64 for example. But I can tell if it's closer to 65 or closer to 60 depending on the level of bite each HRC testing file gives. Even with basic heat treating equipment (Not using a computer controlled evenheat oven) I can reliably estimate the hardness to a certain degree of some 1095, by water quenching, and then tempering at 200 degrees, I know roughly what HRC it will be at, and I know roughly what HRC it will come out if I temper higher at 220 degrees.
Some companies batch test (Not sure about laminated blades those are probably educated guesses) Some companies do individual testing though for each knife, like for example Rockstead are known to individually test each knife, I'm not sure about William Henry, but they do stamp the blades hardness on each knife as well, maybe they do small batch testing, but I know Rockstead do test every knife. Lots of custom makers test every single knife as well, like Big Brown Bear, I see shawn testing every one of his knives after he makes them.
Click to expand...

My Tsubosan testing files that were made in Japan just came in today. They seem to be pretty accurate. My 1990 Buck 301 with 425M steel tested between 60 and 65 Rc. The 65 file bit into the steel and the 60 skated. My Kershaw Launch 1 measured between 55 and 60. Which seems right since their website says that their CPM-154 is 58 - 60 Rc.

Files-Rc-1a.jpg
 
000Robert said:
My Tsubosan testing files that were made in Japan just came in today. They seem to be pretty accurate. My 1990 Buck 301 with 425M steel tested between 60 and 65 Rc. The 65 file bit into the steel and the 60 skated. My Kershaw Launch 1 measured between 55 and 60. Which seems right since their website says that their CPM-154 is 58 - 60 Rc.

View attachment 1533623
Click to expand...

Those are the exact files I have, had to order them directly from Japan, strange that I couldn't find any British or European companies that make them. They are very good and should last a lifetime.
 
A few years ago a friend of mine was the head metallurgist in the engineering lab. I would occasionally wander in on a Friday afternoon when not many folks were around and he would let me use the Rockwell tester. Over time I tested about 30 knives from various mainline makers. I never found one which tested lower than the manufacturer's stated hardness.
 
Less Than Sharpest said:
When I watch a video of someone performing a cutting test, that is with two knives if the same steel, first I admire them for trying, but are they really comparing an apple to another apple?

I'm not an expert, and I welcome your responses. Please let me know what you think. I have carried a couple of different blades in M390, and a couple in 204P and I have some opinions on which steel is better.
Thanks for reading.
dt
Click to expand...

So when you see someone else compare knives with similar or the same steels, they’re doing it wrong, but when you do it, it’s different?
 
I wasn't trying to say that anyone is doing anything wrong. I'm sorry if I gave that impression. I mainly wanted to express that this is a 'soft' science and should be treated that way. Simple carbon steels are wonderful if you like them that way. When I need to cut down a box I look for something that I'm not gonna get irritated when it ends up very dull because I know that it's going to get dull. I have used my ZT 0804 a lot and carry it everyday but I'm not going to use it for every single cutting task. I'll look for a simpler solution, and they're available. And it's fun to look around, to see what's available.

My original point had nothing to do with saying that anyone is doing anything wrong. It's just that there's a lot of complaining and frankly some people enjoy having a forum where they can say whatever they want and not have to ever back it up. I once frequented a knife store that was a place where people could say whatever they wanted, within reason, and opinions were excepted for what they were. There were a lot of opinions! But I don't recall anyone ever telling me I didn't know what I was talking about because at any time I could take their knife and sharpen it back to the point when it was new. I'm not trying to impress anyone here, but that was how it was. I don't recall anyone ever being bent out of shape or having their feelings hurt. Maybe they did.

I have read examples of people testing knife steels and they are very thorough, very careful to make sure everything was as scientific as possible, but those are the exception, not the rule. My main point was that people need to relax a little bit and just use their knife and stop acting as if they knew all. That's the whole point. It's a soft science.

When I was in high school I had a neighbor who had a collection of about 100 Case knives, all displayed very nicely, and one day I asked if I could look at one. Oh no (!) he told me, those are never to be handled. And this was a guy who handed me the keys to his Rolls Royce and let me drive it alone. And I remember thinking that he had his priorities backward. Perhaps...

So back to the question of which steel is better; M390 or 204P. I have some experience with both steels in knives made by ZT, two of either. I have cut a few things over the years, and I have a 0456 that has never cut anything except the hair from my arm. Sorry, it's really a nice blade and perhaps I'm just waiting for something equally nice to appear before I use it. But I mention it because ZT has always done such a great job with sharpening their edges, better than almost any company except for William Henry. So here we have two steels that are very similar in composition and it's natural to want to compare them, and I would have to give a slight nod to M390, based on my own completely biased opinions. I carry and regularly use a ZT 0804CF, and it takes a hell of a edge, no real complaints, but I would have to say that the M390 steel that I've carried and used in the past was just a little better.

But ZDP-189 is still the best steel (!) in my humble opinion. Sorry that it's so hard.

Cheers!
 
Less Than Sharpest said:
I wasn't trying to say that anyone is doing anything wrong. I'm sorry if I gave that impression. I mainly wanted to express that this is a 'soft' science and should be treated that way. Simple carbon steels are wonderful if you like them that way. When I need to cut down a box I look for something that I'm not gonna get irritated when it ends up very dull because I know that it's going to get dull. I have used my ZT 0804 a lot and carry it everyday but I'm not going to use it for every single cutting task. I'll look for a simpler solution, and they're available. And it's fun to look around, to see what's available.

My original point had nothing to do with saying that anyone is doing anything wrong. It's just that there's a lot of complaining and frankly some people enjoy having a forum where they can say whatever they want and not have to ever back it up. I once frequented a knife store that was a place where people could say whatever they wanted, within reason, and opinions were excepted for what they were. There were a lot of opinions! But I don't recall anyone ever telling me I didn't know what I was talking about because at any time I could take their knife and sharpen it back to the point when it was new. I'm not trying to impress anyone here, but that was how it was. I don't recall anyone ever being bent out of shape or having their feelings hurt. Maybe they did.

I have read examples of people testing knife steels and they are very thorough, very careful to make sure everything was as scientific as possible, but those are the exception, not the rule. My main point was that people need to relax a little bit and just use their knife and stop acting as if they knew all. That's the whole point. It's a soft science.

When I was in high school I had a neighbor who had a collection of about 100 Case knives, all displayed very nicely, and one day I asked if I could look at one. Oh no (!) he told me, those are never to be handled. And this was a guy who handed me the keys to his Rolls Royce and let me drive it alone. And I remember thinking that he had his priorities backward. Perhaps...

So back to the question of which steel is better; M390 or 204P. I have some experience with both steels in knives made by ZT, two of either. I have cut a few things over the years, and I have a 0456 that has never cut anything except the hair from my arm. Sorry, it's really a nice blade and perhaps I'm just waiting for something equally nice to appear before I use it. But I mention it because ZT has always done such a great job with sharpening their edges, better than almost any company except for William Henry. So here we have two steels that are very similar in composition and it's natural to want to compare them, and I would have to give a slight nod to M390, based on my own completely biased opinions. I carry and regularly use a ZT 0804CF, and it takes a hell of a edge, no real complaints, but I would have to say that the M390 steel that I've carried and used in the past was just a little better.

But ZDP-189 is still the best steel (!) in my humble opinion. Sorry that it's so hard.

Cheers!
Click to expand...

ZDP-189 is a good steel, when talking about "Best" it really comes down to personal preference in what quality each user desires. ZDP is good and shines when ground thin, much in the same way as VG-10 both shine when you take them down to very low edge angles. I would say many other steels out perform ZDP in other areas though, for example it will never have the high wear quality of Rex 121 or Maxamet. It's not going to be as tough as Elmax or K390. It's not going to take an easier polished fine slicing edge as Shiro white steels. It's going to be more brittle at high hardness than many other steels. It's not very suited for long blades, or heavy choppers it has too much C and Cr.
But in it's own way it is a fine steel usually with good hardness in the mid 60's
Right now I have a few favourite steels, I'm partial to K390, M2 at high hardness, and CTS XHP. XHP actually surprized me for how good it can be with edge stability, you don't often hear much about how great XHP is at taking and holding a razor fine edge, but it performed excellent in all the tests I put it through, I really like Spydercos XHP. Not sure if I got a strangely high HRC batch that was ran a little higher than usual, but my XHP Chap Raffir Noble performed great at holding a fine edge for a long time, without rolling or chipping. I was more impressed with the XHP than the K390 honestly.
We all have our fav steels for different reasons, ZDP is a good steel for a folding knife or slicing blade.
 
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