Why is 13C26 better?

[thombrogan]

This really has made an impact on how people use knives? It changes their scope of work? I have been meaning to look at that because I am looking for a knife for a person with a severe hand disability (rheumatoid arthritis) who has problems with even the better holes/studs.

I think it can be argued that some of the curves on those knives change the amount transferred from the hand to the material being cut at angles not seen on run-of-the-mill recurves and that the Leek made the handiness of wharncliffe pattern rediscovered among people used to using clip-pointed pocketknives. As for the AO, well, it ain't my bag, but my father in law seems to love it. Don't know if it's because of his arthritis or because he loves automatic knives.

Or you can buy any blade and have it regound and rehardened, or do the former yourself in 1-2 hours.

I couldn't do a good heat-treatment by myself. Don't have the equipment or experience.

It would really odd if it didn't, the critical part is the presuppostion.

Good point. I wonder if steel with lower carbide volume is more prone to plastic deformation than higher carbided steel at the same hardness as that would be another factor. It's what I do.

The sister of tactical stainless.

I think it's fun to call such knives 'sporting cutlery.' Sure, the only sports are mumblety pegs and speed food-prep, but it's still fun to say.

There has been mass promotion of the toughness of knives by Thompson and others which use thickness=quality which also tends to stand out to people because of the long standing association of junk with the stamped knives. Just look at kitchen knives and the high priced and much thicker forged knives vs the thin stamped ones.

I volunteer Thom to go door to door and demonstrate the advantages of thin stock.

Thicker knives are harder to bend. Since few folks hit the kitchen store at the mall with a bag of butternut squash and veal shanks, the tests for quality are limited. The weight of that granton-edged santoku that is so thick that the grantons actually matter inspires a confidence which says "Screw you, spiral-sliced ham! You're going down!" louder than a knife which may be more capable of cutting better.

First you volunteer to have my Fallkniven forged and now you want to send me door to door. I feel like the knifeworld Beaker to your Bunsen Honeydew (both my being high strung and you having incurable jaundice...).

 

[Cliff Stamp]

I think it can be argued that some of the curves on those knives change the amount transferred from the hand to the material being cut at angles not seen on run-of-the-mill recurves ...

Yeah, I would like to see more discussion of these aspects compared to "normal" blade patterns and note what is gained for what is lost. I have used some radical blade shapes and while I would not want to carry them as a singluar EDC's, they can be really useful in a lot of situations. They do tend to strike some people as scary though, silly, but true. Even sillier, if you make the knife colorful it tends to compensate.

I couldn't do a good heat-treatment by myself.

Neither can I, however there are lots of people who will. If you have a charming personality like mine, it isn't hard to find them.

I wonder if steel with lower carbide volume is more prone to plastic deformation than higher carbided steel at the same hardness as that would be another factor.

Landes found that the exact opposite happened at the edge. The high carbide steels take more severe damage under direct micro-loading because of the carbide instability, they actually thus test softer. The higher carbide steels will take their revenge though for slicing with coarse finishes and in general all work at a lower sharpness once the edge inhernetly stabilizes through thickening.

As a fairly radical idea, imagine a micro-laminate with a center core of 10 microns full hard AEB-L/W1 with sides of ZDP-189/maxamet. When fully sharpened, the center core achieves maximum push cutting sharpness, but once it wear to the point it achieves geometrical stability then the high carbide sides start to form the edge and now their insane wear resistance takes over. Of course this laminate has some severe problems such as actually making sheets that thin as well as actually grinding the primary so precise so the edge would center on the core.

However assuming machining starts to become far cheaper then the forming/sharpening issues would not be a problem and then there is just the issue of making the laminates which is pretty nontrivial to say the least.

I think it's fun to call such knives 'sporting cutlery.'

Much nicer than than prohibited weapons anyway.

-Cliff

 

[STR]

Yeah, the last part is kind of critical though.

Yes. Perhaps so and I apologize if it hurt you. Perhaps it was your charm that brought that out in me. In an effort to let the water roll under the bridge I'll just add this last bit.

in experimentation, you don't simply let your data constrain your viewpoint.

I agree with you here but I find it hard sometimes to see how you can apply the data collected about a particular steel and what is on paper or in results you may have seen compared to what happens when the human hand is involved with holding it and using it. The CATRA tests for example don't duplicate what we see in use all the time. I don't think so anyway. Does that make sense? I think sometimes you can't always correlate data to what people do with a steel in thier hands. I seriously doubt that the average Joe using these 13C26 blades knows or even notices a difference in the way the knife performs from a 440A or AUS6 blade or one of the knives like your nephew gave you. That is all I mean when I say its working fine in their hands my friend. Nothing more elaborate or technical than observation.

Believe me I like thin. Heck Thom and I see eye to eye on a lot but you put thin in the hands of the masses and, well you just have to see what they do with their knives I guess. Maybe you do and don't see what I see I or something. Anyway I really hate arguing with you. Also, I recognize you know a lot and should probably know by now not to involve myself in technical detailed type metal discussions for most threads where you are posting but in this case I did feel like I could provide somewhat of a real world cross sectional view of how the knives are being used. No matter what the data says or what the steel can be made to do at optimal shapes and hardness people use them for cleaning engine blocks, and spark plugs and really it does that as well as anything else they have had access to. Being tougher it may actually hold up better and save the company a few pennies at the same time.

Perhaps it isn't optimal or even close, but Kershaw is happy with it, I certainly am, even at the current hardness. Truthfully I never really meant to get into all that. I just mention what I see going on with the hands holding the knives. I'll leave the science to you and Landes and others.

STR

 

[Larrin]

The CATRA tests for example don't duplicate what we see in use all the time. I don't think so anyway. Does that make sense? I think sometimes you can't always correlate data to what people do with a steel in thier hands.

Machine or not, I don't know if silica impregnated card stock is similar enough to what we actually cut.

 

[Cliff Stamp]

In an effort to let the water roll under the bridge ...

I was unclear in the above, I don't have any issue with you for any comments you made in the above, I was frustrated at times with some issues that seemed to be unable to be communicated, but that is a reflection on my inability to make a coherent arguement, nothing else.

I had been meaning to ask you if you are interested in making a small custom lockblade, the individual has a severe physical disability so it has to be very easy to open but at the same time very secure once closed (purse carry). I'd also like it to be "pretty", it should have an element of jewlery as well as be a functional knife.

I agree with you here but I find it hard sometimes to see how you can apply the data collected about a particular steel and what is on paper or in results you may have seen compared to what happens when the human hand is involved with holding it and using it.

It is very difficult because you either have to be able to make a sound physics arguement to show for example the forces are directly similar, and given the dynamics are nontrivial it would be very difficult to do so. How generally such connections are made is simply by seeing what works in actual use and then seeing which materials tests show the same pattern.

This is very critical because you can do a machine based test with significant precision and end up measuring something which has no meaning at all. The evolution of the q-fog machines for example are an illustration of that because the origional measurements, while very precise (lots of numbers), had little accuracy.

The CATRA tests for example don't duplicate what we see in use all the time.

Yes, and what is worse is how they are presented which gives a really horrible misrepresentation of how edges actually blunt in use. But again, what you are seeing here mainly is the effect of someone trying to sell a product rather than educate the customer.

I just mention what I see going on with the hands holding the knives.

That is a perfectly valid point of view and could easily be argued to be the most critical. I spent a lot of time handling knives from tradesmen for those exact reasons. My point was more of along these lines :

Lets say there was an individual who made a small utility knife, spending years perfecting a lock design which is highly stable and very strong. It handles impacts, torques and there is no way to release it aside from simply breaking it. However no one uses it seriously, just for cutting papers. To make matters worse, other knives are compared and found to be just as good for light work even when cheaper.

When people ask for knives for significant work they don't mention the knives by the maker who refined his lock. He makes it clear they are capable of much more, they are in fact superior to a lot of the lock types which are supposed to be better. If people would just use them as you designed they would be so much more impressed as they are far more capable than being letter openers. But no one listens.

-Cliff

 

[Sal Glesser]

CATRA's edge tester is, at this time, the most consistent, mechanical method of testing abrasion resistance on edges. CATRA worked very hard to create the tester and fortunately 20 or so companies world-wide have invested the large amount of funds necessary to own one.

Certainly it does not replace "real world testing", but it is an excellent way for a knife manufacturing company to determine if they want to puchase steel.

Many foundries come to manufactures with "buy our steel, it's great". CATRA testing helps decisions.

As far a using the equipment so "sell a product", I think that is an unfare blanket statement. For example, I have posted very few CATRA test results, and when I have, it has been to share our findings, not to "sell" the steel. In fact, I've seen very few posts that used CATRA to push a particular steel. I also read all kinds of posts on "tests" because of interest and the ability to learn. No tests are perfect, but they all help to learn the truth about a steel.

sal

 

[Larrin]

As far a using the equipment so "sell a product", I think that is an unfare blanket statement. For example, I have posted very few CATRA test results, and when I have, it has been to share our findings, not to "sell" the steel. In fact, I've seen very few posts that used CATRA to push a particular steel. I also read all kinds of posts on "tests" because of interest and the ability to learn. No tests are perfect, but they all help to learn the truth about a steel.

I agree, you rarely see any CATRA results from the companies that have them, it would be pretty cool if more of the information was available. Also, I don't think CATRA designed their machine to make anyone's knives look good.

 

[db]

Talking about real world use rather than theory or second hand info I still wonder.

I cann't find it so I'll just ask. Cliff what knife do you have or used that has this blade grind and heat treatment of 13c26 that you are promoting?

Or has anyone in this thread used or tested one?

 

[Larrin]

Talking about real world use rather than theory or second hand info I still wonder.

Or has anyone in this thread used one?

I think I've already said I've used several knives with AEB-L and 12C27.

 

[STR]

Please know that I am not dismissing the CATRA testing or those involved with the development of it or those that currently use it. I'm just saying that when a human is involved there are always variables. No two people use a knife the same way, look at sharpness or even overall performance the same way so its very hard to let a machine tell you some things or all things that are going to be possible with a blade or a steel. Anyone thats been to a cutting performance contest knows this I think.

My understanding is that the CATRA testing is limited to slicing cuts only so my first question when I heard that was ok, what about push cuts? But thats another topic though. All I was ever saying is that its basically always subjective when it comes to data vs hands on testing and performance. I say these knives work, Cliff says not and thats fine, its just uncomforable bickering about it and I was trying to put a stop to it. Perhaps the CATRA tests were not the best one to mention.

STR

 

[Cliff Stamp]

As far a using the equipment so "sell a product", I think that is an unfare blanket statement.

There are exceptions, Spyderco doesn't tend to use it in that manner from what I have seen. However there are some horrible misconceptions about edge holding and performance in general from how it is used. These were not created by CATRA data, they were around long before it from what I have seen.

One of the biggest problems for example is that the blunting responce is nonlinear. I took CATRA data awhile ago from Buck and showed the exact curves which the data followed and showed a number of things, such as for example at what point you compare sharpness will change the cut ratio as well as if you compare the cuts needed to achieve a specific level of sharpness.

What is usually done however is that some specific point is chosen and the cut ratio used to argue a general measure of edge retention. This is quite frankly very misleading for many reasons. Note for example if you compare AEB-L vs S30V in CATRA work then AEB-L will perform very poorly, AEB-L has a very low abrasion resistance compared to S30V.

However does it mean that AEB-L has inferior edge retention. No. But is this how it is commonly used - yes. What it means is that if you compare those steels at that particular angle for slicing cuts into abrasive material to a specific point of blunting then that cut ratio will be obtained. Note all the constraints.

Landes showed that while AEB-L with the above heat treatment I quoted would fall behind steels like 154CM in regards to long term such as CATRA type edge retention, it was superior to holding a high push cutting sharpness at low edge angles. Thus it had better edge retention in that respect as do all steels of that class when they are very hard.

As I noted, Johnston showed the same thing with the same steel classes with acute edges, as have Elliott and Beach. This isn't an issue of theory it is a general point about the behavior of low carbide steels. To be very clear, all low carbide steels have that behavior. It is just as fundamental as noting that a large carbide volume gives high wear resistance or that chromium provides corrosion resistance.

Note the fact that certain steels can hold a finer polish at a lower angle means you need to test different angles for each steel to show their optimal results and as well present push vs slicing results as they will be very different. Or at very least make it clear that this is the case and don't infer general behavior which doesn't hold.

Further, consider Buck found the Ionfusion blades completely went off scale on the CATRA results so much they had to stop using them as the numbers were meaningless. They didn't represent the actual behavior of the knives in use by people. Yes they measured something very precisely but they had no accuracy. Now once you accept this then it becomes a fundamental issue which you have to consider in general.

There are still other issues such as for example bushcraft knives which see significant impacts and that becomes the critical factor in edge retention, not abrasion resistance. Does such testing have a use - of course. All measurements are by defination meaningful and precision is in general always a good thing. The tricky part is figuring out what they are actually measuring and how to interpret it.

-Cliff

 

[db]

Yes Larrin you've said you have used it at 60-61 RC, I give your comments on it alot of weight and credibilty. I believe the hardness Cliff is talking about is harder 64 RC and with a very low edge angle and extremely thin blade grind. To date I don't think I've read that anyone has even used such a blade, exsept for maybe Landes and I'm not even sure how or if he has used such a blade.

 

[Larrin]

Yes Larrin you've said you have used it at 60-61 RC, I give your comments on it alot of weight and credibilty. I believe the hardness Cliff is talking about is harder 64 RC and with a very low edge angle and extremely thin blade grind.

64 Rc isn't at all feasible. You get 64 Rc as quenched, what are you going to do, temper at 212F?

 

[Cliff Stamp]

You get 64 Rc as quenched ...

With what austenization temperature? Considering that you can put 0.6% of carbon into solution, assuming you can minimize the retained austenite, you should be able to move way past 61 HRC easily. Martensite hardness just depends on carbon content and percentage of retained austenite (assuming noninsane carbide levels). 12C27 gets 62 HRC with a 325F temper from 1975 F with oil/cold and 13C26 has a higher maximum hardness. That is an average of course, you would expect it to bounce around that given variances in the steel and heat treatment. Given what Wilson has noted with other steels, likely about 1 point or so.

Sandvik recommends a lower austenization for 13C26 but that is because of issues with retained austenite due to the higher alloy content assuming no cold treatment. The last part is critical and since buck and case have been using cold for forever you really don't want to use such a viewpoint. With proper cold treatements (no delays) this should not be an issue for such a low alloy steel and thus you can raise the hardness further.

What I am really curious about is 13C26 vs 1095 when they are both full hard. 1095 at 66 HRC vs 59 HRC stainless isn't overly interesting as it has already been done, that is also no different than 420J2 vs 420HC. Not really much of a fight. However 13C26 has a small volume of chromium carbides which are significantly harder than the cementite in 1095 and thus that actually could make it more stable with higher wear resistance or at very least comparable.

There are some other interesting questions as well. For example the Byrd steel is on the same tie line as 13C26, just to the right so it has a higher wear resistance at a lower edge stability. That is straightforward. However what isn't well known is the exact intersection point of those steels. How blunt do the blades have to get before 13C26 falls ahead signifiantly, how much lower of an angle can it take. What happens when you compare them both at the optimal angles.

This isn't even well known exactly for 13C26 vs ATS-34. It is known in general what happens, but not the specific intersection points, cut ratios, etc. . It is further complicated by manner of cutting, different angles, exact hardening, etc. .

-Cliff

 

[Larrin]

With 1925F and cryo, 63 is common, with an occasional 64. If you move up to 1975F, 64 Rc is more common. We typically stick with 1925F for greater toughness and for the reason that we think 59-61 is generally plenty of hardness.

 

[db]

Maybe I misspoke with the 64 RC, because I have seen the following and that is how I came up with it.

13C26 has inhernetly greater edge stability than 12C27M not less, so it should offer greater performance at more acute angles.



Yes, depending on the knife it would be full deep hollow or high flat. The heat treatment would be oil+cold for maximum as quenched hardness and tempered low to maximize edge stability. /QUOTE]

Typical as quenched (with cryo) hardness is 63-64, so to get 63 you'd have to have an extremely low temper, probably less than 300F.

To be fair looking through this thread I’ve seen 62RC was specifically asked for as a hardness. Also, I've seen full hard asked for, with a very thin blade grind and very low edge angles with that hardness. Have you used one like that?

 

[Larrin]

To be fair looking through this thread I’ve seen 62RC was specifically asked for as a hardness. Also, I've seen full hard asked for, with a very thin blade grind and very low edge angles with that hardness. Have you used one like that?

Every knife I've used starts with blade stock of .125" or less, and is flat or convex ground to zero, I don't know much about angles or thicknesses behind the edge, I've never worried about them. The highest hardness I've used was 61 Rc.

 

[Cliff Stamp]

We typically stick with 1925F for greater toughness ....

You actually have people impacting/prying the blades and seeing issues with brittle failure? Spyderco is running ZDP-189 at 65 HRC and that is much more brittle than AEB-L.

I really would like to understand the reasoning behind "plenty of hardness". The gain in strength you see from 56 to 60 is similar to 60 to 64, and generally there is also a linear gain in wear resistance. Unless there is a strong peaked behavior due to secondary carbide precipitation, the toughness is also linear as well. Stainless steels do have a peak, which is a concern toughness wise, but it is much higher, 950F or so.

-Cliff

 

[Larrin]

You actually have people impacting/prying the blades and seeing issues with brittle failure? Spyderco is running ZDP-189 at 65 HRC and that is much more brittle than AEB-L.

I really would like to understand the reasoning behind "plenty of hardness". The gain in strength you see from 56 to 60 is similar to 60 to 64, and generally there is also a linear gain in wear resistance. Unless there is a strong peaked behavior due to secondary carbide precipitation, the toughness is also linear as well. Stainless steels do have a peak, which is a concern toughness wise, but it is much higher, 950F or so.

-Cliff

By the same token, corrosion resistance can always be higher than the steels we typically use in knives, and we could all be using S5 if we don't think our steels have enough toughness. We haven't found the edges to roll, or seen premature blunting from "micro-rolling" or whatever it would be called. Of course, you could simply say that that is only the case for our uses, or that we haven't looked at it astutely enough to see it, but obviously, we haven't noticed any reason for an increase in hardness. I agree that for our preferred type of grind, higher hardness could be benificial. When I finally get to testing knives, it will be something to observe, and something I plan on doing. The problem is I'm still in limbo because of Darrin taking forever with his knives, after these knives I'll stick with my father and myself.

 

[Cliff Stamp]

By the same token, corrosion resistance can always be higher than the steels we typically use in knives, and we could all be using S5 if we don't think our steels have enough toughness.

These properties are different in the manner they effect edges, essentially one of the curves has a horizontal asymptote and the other does not. All edges blunt from wear/deformation, it just happens less as the hardness is increased. However with shock and corrosion you can actually prevent it completely with a specific amount of a property and thus increasing it has no functional gain.

-Cliff