O1 vs 5160

AcridSaint said:
OK, now that we've seen that not only can I read the same data sheets you can, but I also own them, can we get on to the part where you show us properties in S5 that are desirable in a knife?
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My friend I'm happy to discuss this with you and others in detail, but you should not assume to know things about what I may or may not have done.

The reason I moved to shock resisting materials is that for my needs, which are hard use, the failure mode involved a lack of toughness. I am fully happy too resharpen a blade to restore the edge - wear resistance is not number one for me. I cant field fix a shattered blade or indeed a blade that has plastically deformed. I think we can all agree that if that was the key criteria none of us would be using tool steels and we would shift out attention to cermets and other composites such as Ceramics.

Crucible are not the exclusive authority on what shock resisting tool steels are used for. That category of tool steel is also commonly used for blanking knives and shredding knives. I prefer Carpenter for my supplies anyway.

Material selection depends on what the engineer wants out of the desired properties. For me, much trial and error has shown it is:

1. Toughness as first priority
2. Strength as second priority
3. No materials under 58 Rockwell C

When I went through all the materials I could think of I settled on S5. Yes, I have made blades out of S5 as well as other materials including S7, 52100, 5160, micro melt maxamet, aermet for tooling, 1095, others Ive probably forgotten. The S5 knife is so far the best blade Ive made for my use. I find its toughness prevents catastrophic failure much better than less tough materials Ive used and the down side of more regular sharpening is fully acceptable for my use. My adventures continue and I hope to improve my style of knives as time goes on with the best science has available to me. Its likely when Im happy with my hard use knives I'll move onto some kitchen knives probably starting with micro melt maxamet alloy as its wear resistance is almost comparable with some sintered cerments but has more toughness.

One thing I'm interested in with what you say mate, is that I have not found any definitive studies that shows what types of wear knives are subjected too under different use modes. You mention abrasive wear specifically, but Im sure your aware there is other forms of wear. Id be interested in you sharing any studies you might find on this.

What I have been thinking about lately is having an open source knife makers project. What Im talking about here is keeping everything out in the open. Using FEA we could come up with different studies in hard use, kitchen use, skinning use, butchering use etcetc and use those models on a supercomputer to compare how different materials perform, how different dimensions perform etcetc. Before people dismiss FEA as being a "theory" thing it really isnt and there is airplanes / military gear / cars etcetc that are prototyped exclusively in FEA and have them pass rigorous real world tests just as the FEA study showed. FEA is a central part of modern design. I dont know if fellow knifemakers would be interested and it would be a big project but I think it could give us allot of highly useful information. There is so many different things we could try that having to build them all in reality is too limiting.

cheers
 
Also folks I forgot to mention that when I called carpenter for my order I also discussed with them the abrasive wear characteristics of S5 vs S7. What I was advised was that in terms of abrasive wear (which is not the only type of wear) both steels are similar but in fact S5 has better abrasive wear resistance between 55 and 62 HRC than S7. I goto HRC 60 on mine as I know that there is a rapid drop off in toughness at HRC 62 and 61. The bloke said he had a paper on this and he would send me a copy of the study so if you like when I receive it I will share the conclusion of that too.
 
nullack said:
What I have been thinking about lately is having an open source knife makers project. What Im talking about here is keeping everything out in the open. Using FEA we could come up with different studies in hard use, kitchen use, skinning use, butchering use etcetc and use those models on a supercomputer to compare how different materials perform, how different dimensions perform etcetc. Before people dismiss FEA as being a "theory" thing it really isnt and there is airplanes / military gear / cars etcetc that are prototyped exclusively in FEA and have them pass rigorous real world tests just as the FEA study showed. FEA is a central part of modern design. I dont know if fellow knifemakers would be interested and it would be a big project but I think it could give us allot of highly useful information. There is so many different things we could try that having to build them all in reality is too limiting.

cheers
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I really find it hard to track your thought process. One moment you dismiss comments on several years of testing and refinement of a process of heat treating a steel made by a pillar of the knifemaking community as being anecdotal and not worth spit and here you are asking for a whole bunch of anecdotal testing results. What gives?? There have been a number of instances where I've been reading your comments and I can't help but think, Troll! Maybe I'm overreacting.
 
69_knives said:
I really find it hard to track your thought process. One moment you dismiss comments on several years of testing and refinement of a process of heat treating a steel made by a pillar of the knifemaking community as being anecdotal and not worth spit and here you are asking for a whole bunch of anecdotal testing results. What gives?? There have been a number of instances where I've been reading your comments and I can't help but think, Troll! Maybe I'm overreacting.
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Similar arguments appear on other forums as well. I am no great knifemaker, but I have made a few, I really would like to know how many knives John Nullack has made. When people bring up a good counter point and ask questions or ask for references, he seems to just ignore them.
 
The usual argument is that folks would rather their blade deform because it can be fixed in the field. I am interested to know what kind of hard use the knives are going through that they suffer from either serious deformation or shattering. It takes quite a bit of force to put a set in a well heat treated blade. Judging solely by your criteria, S5 is likely the best steel for you, but I still don't see where it is an ideal knife steel in the majority "hard-use" scenarios where a blade might see impact.

Something else to consider are the carbides in S5. I haven't looked into this, but I think that it would be interesting to see how it compares to other "knife steels".

Have you looked at 3V for your hard-use knives? At your 58RC minimum, you are looking at 85ft lbs of impact toughness and a very high amount of wear resistance. In my opinion, this is a much more suitable "high-impact" knife steel.
 
69_knives said:
One moment you dismiss comments on several years of testing and refinement of a process of heat treating a steel made by a pillar of the knifemaking community as being anecdotal
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Im sorry if your offended. The problem with communication on the net is that sometimes things are read into statements which are not intended. It lacks that human quality of talking about our hobby in person.

I dont specifcally see what your objection actually is to doing a set of FEA studies - FEA results are in no way anecdotal, it is indeed used to crunch the numbers for coming up with highly accurate metrics.
 
AcridSaint said:
I am interested to know what kind of hard use the knives are going through that they suffer from either serious deformation or shattering.

Have you looked at 3V for your hard-use knives? At your 58RC minimum, you are looking at 85ft lbs of impact toughness and a very high amount of wear resistance. In my opinion, this is a much more suitable "high-impact" knife steel.
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My application usually involves the knife being used for things that are not ideal for such a tool in the absence of a saw / axe / hammer due to weight limits on hiking and similar.

Thanks for the suggestion on CPM3V. I havent made any knives from it and I'll look into it.
 
Sam Salvati said:
When people bring up a good counter point and ask questions or ask for references, he seems to just ignore them.
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Im happy to listen to reasoned criticism because afterall, that can only improve my knives. Rather than assume the worst, you could also consider I did not see the question or I my time was demanded elsewhere and I forgot about it. Ive been more than forthcoming about my tests and process - no secrets.
 
nullack said:
I dont specifcally see what your objection actually is to doing a set of FEA studies - FEA results are in no way anecdotal, it is indeed used to crunch the numbers for coming up with highly accurate metrics.
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I have no objection but you have made it pretty clear in several statements that if testing isn't done scientifically under laboratory conditions the results aren't worth spit and you dismiss them as being anecdotal.
 
69_knives said:
if testing isn't done scientifically under laboratory conditions the results aren't worth spit and you dismiss them as being anecdotal.
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I did not say anecdotal results are worthless. If you actually ask me that question my response is that anecdotes are interesting :) What I was trying to imply about having data to backup claims is that it shows what we think we are observing against what is actually happening in an objectively measured way. It richens our pitcure of whats going on. For example if Ed had of measured the HRC values against grain size and then graphed them that would help him and others to make the right decisions. Plus when we know exactly whats going on it leads us into coming up with solutions - like changing quenchants for a faster quench to combat the smaller grain size hardness issue.
 
You can argue which steel is better for which aplication all day and then some. To me, whichever steel you've better mastered the heat treat on would be the choice. That said I wouldn't use 440C for a camp knife or 1095 for a dive knife. Outside of that most carbon steels properly heat treated for there intended use will work great.

The highest performance magical steel out there with a poor heat treat will do no better than simple carbon and iron with a heat treat by somebody who knows what there doing.

Me personaly I love L-6 and 5160 for big tough knives, and 52100 for medium to smaller knives, though I did make a 12'' bowie from 52100.
 
For sure Will, a bad heat treat will wreck any blade.

I see material choice as being like a triangle between Toughness, Strength and Wear Resistance that has many different optimal points depending on intended use. All of these three things are well understood in classical solid mechanics and dynamic mechanics. What seems not to be very well understood in engineering terms is the tribology of knives in use - i.e. how they wear. When I tried to talk with subject matter experts about tribology in knives the questions they ask cant be properly answered because I dont know the correct answer. I cant find any papers studying it either.

I think that there is one best material a knife can be made from provided the intended use is very specific and well understood. Otherwise if thats not the case I agree with your assertion that it becomes a circular argument because of the lack of definition or generalisation around what it needs to do.
 
From "Tool Steels", 3rd. Ed., Pg. 59

"Before discussing that phase of mechanical testing in which a stress is applied and the reaction to that stress observed let us establish what might be considered a logical definition for toughness since toughness is a highly desirable property in any type of tool steel. Toughness can be defined as a combination of two factors:

1. The ability to deform before breaking which represents the amount of plastic plus elastic deformation up to the point of failure (ductility).

2. The ability to resist permanent deformation or the elastic strength of the material (strength)."

Strength is an aspect of toughness. Strength is yield strength. My opinion is most knives need to be of a steel and HT that fails by yield strength, not plastic/elastic. That if a person wants to talk about the fat part of the bell shaped curve that is knives in relation to toughness, high yield strength is the definer.

Mike
 
I guess we need a new question...

Which one steel will allow us to use a knife as 1) a Knife, 2) a Prybar and 3) a chisel?
 
Mike Krall said:
Strength is an aspect of toughness. Strength is yield strength. My opinion is most knives need to be of a steel and HT that fails by yield strength, not plastic/elastic.
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Gday Mike. I think there is some confusion over terms. Can I offer some basic defintions in general terms (I dont have time right now to look up text book defintions):

* the yield strength is the point in force where the material gives (yields) under the load

* The elastic range is the part of the stress / strain curve under the yield strength. i.e. It bends according to the modulus of elasticity but does not permanently deform.

* The plastic range is the bit above the yield point where the material stops its elastic movement and goes into permanent deformations

* toughness is different to strength in that yield strength, compression strength, tensile strength etcetc mean specific things. Toughness has different types of tests such as izod and charpy tests with different unnotched and notched test samples are subjected to shock loads which is different to the loads in say in an ultimate tensile strength test. Some materials like glass can be pretty strong but not tough.
 
Strength is just hardness, no? It's measured by deformation of the steel against a diamond indenter.

I like 5160 for toughness. In applications where extreme toughness is needed, like heavy chopping, abrasion resistance is not needed. In applications where a lot of abrasion resistance is needed (like cutting), not much toughness is needed. That's been my experience, and besides, there are steels that are both very tough and wear resistant like CPM-3V and CPM-M4.
 
No mate strength is a separate property. There are three stresses - tensile / compressive / shear where they are each specifically tested and reported on e.g. ultimate tensile strength in mpa or psi for your imperial folk. In hardening our steels there is a relationship to the hardness vs strength but they are different mechanical properties.
 
I knew better than to start in on word definition... here's an apology to you all.

L6 is a very tough, readily forged steel with higher carbon amount than 5160. L6 is very tough at it's carbon amount or 0.70% to 0.75%.

Mike
 
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