# Which Steel Has the Best Edge Retention?



## Larrin (Nov 19, 2018)

I convinced a major knife company with a CATRA tester to send me a giant database of their testing results. I used that database to figure out the relative effects of different variables on edge retention in knives. Enjoy. https://knifesteelnerds.com/2018/11/19/steel-edge-retention/


----------



## Interapid101 (Nov 19, 2018)

Another great article. In the part where S90V was compared to D2 by cross cylinder wear test, what were the measurement units? I was confused by the notation. Does this test measure how much pressure is required to achieve a fixed depth of wear?

You mention that the composition of carbides is not always known, and it occured to me how difficult it must be the experimentally determine that. How is this normally done? It seems a hybrid imaging-elemental analysis method would be ideal. Is it possible to do X-ray fluorescence or laser ablation mass spec? Or are the carbides just too small to sample this way? If so, are wet chemistry techniques used? Must be a huge pain in the ass.

Regarding the regression of predicted/measured TCC, when you mentioned that using a nonlinear expression for edge angle, the regression improved. Is there a theoretical or mechanistic basis to explain/justify use of a nonlinear expression, or was nonlinearity just empirical? Looking at the TCC versus edge angle, nonlinearity is apparent, but I wonder if this is, in part, a function of the cardboard use in the test? I wonder if a different test material was used, would the “shape “ of the TCC vs edge angle plot look different. 

Seems like the company must be Spyderco.


----------



## Larrin (Nov 19, 2018)

Interapid101 said:


> Another great article. In the part where S90V was compared to D2 by cross cylinder wear test, what were the measurement units? I was confused by the notation. Does this test measure how much pressure is required to achieve a fixed depth of wear?










> You mention that the composition of carbides is not always known, and it occured to me how difficult it must be the experimentally determine that. How is this normally done? It seems a hybrid imaging-elemental analysis method would be ideal. Is it possible to do X-ray fluorescence or laser ablation mass spec? Or are the carbides just too small to sample this way? If so, are wet chemistry techniques used? Must be a huge pain in the ass.


Typically the carbide fractions are measured either with X-Ray Diffraction (XRD) or directly with microscopy of an etched cross-section.


> Regarding the regression of predicted/measured TCC, when you mentioned that using a nonlinear expression for edge angle, the regression improved. Is there a theoretical or mechanistic basis to explain/justify use of a nonlinear expression, or was nonlinearity just empirical? Looking at the TCC versus edge angle, nonlinearity is apparent, but I wonder if this is, in part, a function of the cardboard use in the test? I wonder if a different test material was used, would the “shape “ of the TCC vs edge angle plot look different.


I can only say what the CATRA data gave. It is possible that other test media, applied load, sharpness measurement, etc. may lead to different results. 


> Seems like the company must be Spyderco.


I can neither confirm nor deny that the company is Spyderco.


----------



## Ruso (Nov 19, 2018)

Interapid101 said:


> Seems like the company must be Spyderco.



Reading the article I though the same.

@Larrin Nice article.


----------



## Chef Doom (Nov 19, 2018)

VG 10 at a 90 degree angle holds an edge forever.


----------



## pennman (Nov 19, 2018)

So the predicted TCC of AEBL is between 410 and 440a steels? Am I reading that correctly?


----------



## Larrin (Nov 19, 2018)

pennman said:


> So the predicted TCC of AEBL is between 410 and 440a steels? Am I reading that correctly?


That depends on what hardness you are assuming.


----------



## pennman (Nov 19, 2018)

Larrin said:


> That depends on what hardness you are assuming.


What hardnesses were tested?


----------



## Matus (Nov 20, 2018)

Very interesting article, thank you. But do I interpret it correctly that since different ways to test the abrasion resistance lead to different results (the two tests that compared D2 and S90V) - this could mean that sharpenability and edge holding are not necessarily 100% correlated? 

Do you also have some data on SC1 (Niolox) steel by any chance?


----------



## Larrin (Nov 20, 2018)

Matus said:


> Very interesting article, thank you. But do I interpret it correctly that since different ways to test the abrasion resistance lead to different results (the two tests that compared D2 and S90V) - this could mean that sharpenability and edge holding are not necessarily 100% correlated?


That is correct.


> Do you also have some data on SC1 (Niolox) steel by any chance?


1% MC, 8% CrC
https://knifesteelnerds.com/2018/03/16/micrographs-of-niolox-cpm-154-and-aeb-l/


----------



## Matus (Nov 20, 2018)

Thank you Larrin.


----------



## inferno (Nov 23, 2018)

so. which steel actually had the best edge retention???


----------



## Ruso (Nov 23, 2018)

inferno said:


> so. which steel actually had the best edge retention???


Did you even RTFA or at least the Summary?
...15V or Rex 121...


----------



## DitmasPork (Dec 22, 2018)

Larrin said:


> I convinced a major knife company with a CATRA tester to send me a giant database of their testing results. I used that database to figure out the relative effects of different variables on edge retention in knives. Enjoy. https://knifesteelnerds.com/2018/11/19/steel-edge-retention/



Firstly, my knowledge of modern steels is very limited, most of my knives are carbon.

My question for you is, is there a significant difference in judging edge retention for kitchen knives vs other types of knives?

Reason I ask, is that I've just read an article on Knifeinformer, where it judged knife steels on edge retention/corrosion resistance/ease of sharpening.

The steel that they rated highest for edge retention was CPM S110V—followed by CPM S90V and M390. Is there a reason why I rarely see Chef's knives made in those steels? Is it cost, or difficulty in making knives with them, or availability, or lack of demand?


----------



## Eloh (Dec 22, 2018)

These steels are a pain to grind. So lots of pricey belts. Lots of hours on the grinder. And probably not nearly enough demand/users who know how to sharpen those correctly. 


I'll get a T1 San mai gyuto soon though, wich has a crazy amount of tungsten (18%). It's more of a old-school hss though without pm. Probably not the best choice but I'm just curious about these extreme steels

The craziest steels would probably be Rex121 and S290. But that almost tungsten carbide territory ..


----------



## Matus (Dec 22, 2018)

Those high alloy steels are not only pain to grind and hand sand (just don’t), but also a pain to sharpen and thin (later down the road).

Nearly every pro user would prefer a knife that lasts a month in a pro kitchen instead of just a few days before it needs to be sharpened, but most also prefer to be able to sharpen a knife in a few minutes instead of one hour.


----------



## DitmasPork (Dec 22, 2018)

Matus said:


> Those high alloy steels are not only pain to grind and hand sand (just don’t), but also a pain to sharpen and thin (later down the road).
> 
> Nearly every pro user would prefer a knife that lasts a month in a pro kitchen instead of just a few days before it needs to be sharpened, but most also prefer to be able to sharpen a knife in a few minutes instead of one hour.



Sounds like the cons of a high edge retention super steel are:
• Difficulty in knife production.
• Because it's hard to sharpen, not very practical with chefs.


----------



## Eloh (Dec 22, 2018)

Matus said:


> Nearly every pro user would prefer a knife that lasts a month in a pro kitchen instead of just a few days before it needs to be sharpened, but most also prefer to be able to sharpen a knife in a few minutes instead of one hour.



With 0.1mm or less behind the edge sharpening on stones is a matter of minutes even with m390, hap40 and the likes.
With a super thin edge you can last a long time without thinning. If it's time for thinning a belt grinder is a must though lol

So with these steels the key is a super thin edge and careful sharpening without taking away too much material.


----------



## DitmasPork (Dec 22, 2018)

Eloh said:


> With 0.1mm or less behind the edge sharpening on stones is a matter of minutes even with m390, hap40 and the likes.
> With a super thin edge you can last a long time without thinning. If it's time for thinning a belt grinder is a must though lol
> 
> So with these steels the key is a super thin edge and careful sharpening without taking away too much material.



From a knifemaker's perspective—which I know little about—are steels like CPM S110V, m390 and hap40 much more challenging with heat treatments, etc.


----------



## panda (Dec 22, 2018)

damascus makes edge last longer, and so does jnat polishing he blade face. kato ku finish lasts the longest.


----------



## Barmoley (Dec 22, 2018)

Matus said:


> Those high alloy steels are not only pain to grind and hand sand (just don’t), but also a pain to sharpen and thin (later down the road).
> 
> Nearly every pro user would prefer a knife that lasts a month in a pro kitchen instead of just a few days before it needs to be sharpened, but most also prefer to be able to sharpen a knife in a few minutes instead of one hour.



This is where San mai would shine and actually makes sense. Take one of these steels and use it for a thin core, so that you only have to sharpen a very thin piece of steel and have the outside be something that is easy to thin when needed. Also would aid in making as you can have more complex grinds without having to deal with the hard to work core steel. Not as simple as it sounds ofcourse but just saying.


----------



## Matus (Dec 22, 2018)

Barmoley, I agree, but samai might require an industrial pre-clad stock as I expect these kind of steels are going to be very hard to forge-weld for very most knifemakers. And I am not even sure how different the forging temperatures for the cladding and the core steel are going to be - maybe stock removal would be the best option here.


----------



## Barmoley (Dec 22, 2018)

Yeah, I am sure not simple, but in theory good combination of getting a great edge performance without the pitfalls of the other issues. Devin in another thread said that he forge welded many of the “super steels” and I know that pd1, T1, Rex-121, Vanadis 10, etc can be forge welded. Most will require industrial preclad stock I am sure and will be difficult to heat treat, etc. 

Stock removal once the preclad stock exists would be a perfectly fine way to go. I am only talking about possible way of getting hard to work with steels into kitchen knives, not how the knives are made, any method works great if the result is good.


----------



## DitmasPork (Dec 22, 2018)

Barmoley said:


> Yeah, I am sure not simple, but in theory good combination of getting a great edge performance without the pitfalls of the other issues. Devin in another thread said that he forge welded many of the “super steels” and I know that pd1, T1, Rex-121, Vanadis 10, etc can be forge welded. Most will require industrial preclad stock I am sure and will be difficult to heat treat, etc.



Do you foresee these "super steels" eventually used for chef's knives, produced at a reasonable price point? I see them listed more with Spyderco and other EDCs, than with kitchen knife makers.


----------



## HRC_64 (Dec 22, 2018)

DitmasPork said:


> Firstly, my knowledge of modern steels is very limited, most of my knives are carbon.
> 
> My question for you is, is there a significant difference in judging edge retention for kitchen knives vs other types of knives?



Most folding knives are sub 4 inch cutting length, so often its more wear on less surface/lenght/area so more need for higher retention per unit steel. On the other side (practicality of sharpening), mainting a 3 inch folder vs a 9 inch chef knife is ~ 1/3rd the hassle.. so...

{more need} x {less hassle} = different market equilibrium

KKFers seem to like longer knifes which distribute wear (multiple sweet spots), 
and have easier to sharpen substrates (often hitatchi carbon)...etc


----------



## HRC_64 (Dec 22, 2018)

panda said:


> damascus makes edge last longer, and so does jnat polishing he blade face. kato ku finish lasts the longest.



you forgot the part about eating the jnat mud, i hear this gives the user even more edge


----------



## Barmoley (Dec 22, 2018)

HRC_64 said:


> you forgot the part about eating the jnat mud, i hear this gives the user even more edge


Also whitens teeth I hear......


----------



## Keith Sinclair (Dec 23, 2018)

Eloh said:


> With 0.1mm or less behind the edge sharpening on stones is a matter of minutes even with m390, hap40 and the likes.
> With a super thin edge you can last a long time without thinning. If it's time for thinning a belt grinder is a must though lol
> 
> So with these steels the key is a super thin edge and careful sharpening without taking away too much material.



Agree with this. My M390 spyderco is thick behind edge did knock off the shoulders of the V grind. Made it a little easier to sharpen. Would not attempt major thinning. Use it a lot has good edge retention and is stainless. Hap 40 can sharpen up in a few minutes to a fine edge. Only Hap40 knives I know of are stainless clad over core steel even the Spyderco. The Gihei Hap40 has much better geometry than the Kohetsu hap40. Even calling it semi stainless is a stretch. That's not a bad thing. The Gihei and Takamura R2 largest size is 210mm they are reasonably priced have better edge retention than most knives. Because of the grinds both are easy to sharpen.


----------



## bkultra (Dec 23, 2018)

*back on track*


----------



## Chef Doom (Dec 23, 2018)

I need do some extensive research to discover what steel chainsaws are made of. They are always around in workable condition under any circumstances in every post-apocalyptic film so the steel has to be awesome. [emoji108]


----------



## panda (Dec 23, 2018)

damn it, my response to that invasion was perfect though!!


----------



## Keith Sinclair (Dec 23, 2018)

Chef Doom said:


> I need do some extensive research to discover what steel chainsaws are made of. They are always around in workable condition under any circumstances in every post-apocalyptic film so the steel has to be awesome. [emoji108]



Anything goes in Hollywood. In the real world chains are replaced a lot. You can sharpen the teeth to get more life out of a chain.


----------



## Larrin (Dec 23, 2018)

Chef knives also use a lot of steel compared to a folder. The extra cost of S110V or M390 along with the extra cost and time from grinding and finishing all of that highly wear resistant steel makes it less desirable to the maker. That plus what is already being done tends to be copied.


----------



## Nemo (Dec 23, 2018)

Keith Sinclair said:


> Anything goes in Hollywood. In the real world chains are replaced a lot. You can sharpen the teeth to get more life out of a chain.


I will get anywhere from 1/2 tank of fuel (really dry, dirty aussie hardwood) to half a dozen tanks (clean softwood) before needing to sharpen.

If the chain kisses the dirt- it needs a sharpen. Hit a rock and you'll have a bigger sharpening job. Or a new chain. 

IIRC, the cutters are mostly pretty soft steel, with just the top and side plates being hard. A bit like a single bevel knife, I guess.


----------



## Keith Sinclair (Dec 24, 2018)

Exactly you have to be careful what you are cutting into to preserve chain life.


----------



## Keith Sinclair (Dec 24, 2018)

Larrin said:


> Chef knives also use a lot of steel compared to a folder. The extra cost of S110V or M390 along with the extra cost and time from grinding and finishing all of that highly wear resistant steel makes it less desirable to the maker. That plus what is already being done tends to be copied.



That makes sense. I figured the popularity of R2 powder steel with many quality knife makers is because it works well for kitchen knives.


----------



## pennman (Dec 24, 2018)

Larrin said:


> Chef knives also use a lot of steel compared to a folder. The extra cost of S110V or M390 along with the extra cost and time from grinding and finishing all of that highly wear resistant steel makes it less desirable to the maker. That plus what is already being done tends to be copied.



Those properties are the ones that make them
Most desirable. Incredible edge holding and performance and a technical challenge to make. And performance that exceedes practically everything else on the market.


----------



## never mind (Dec 25, 2018)

That is true and a very sick idea.


----------



## Interapid101 (Dec 25, 2018)

pennman said:


> Those properties are the ones that make them
> Most desirable. Incredible edge holding and performance and a technical challenge to make. And performance that exceedes practically everything else on the market.



Most desirable by who? Isn’t desirability subjective? Don’t exotic alloys come with trade offs? For folks that sharpen their own knives, it seems that wear resistance doesn’t typically top the list of desired steel attributes. Personally, I like stainless with good edge retention for pocket knives, but I prefer kitchen knives that are easily sharpened and that take a keener edge.


----------



## Matus (Dec 25, 2018)

In one of the articles Larrin showed that toughness of steel is closely related to amount of carbides thus one may experience chipping more easily with high alloy steels. One may want to counteract that with larger sharpening angle - but that (as another article from Larrin shows) decreases the cutting ability rather quickly.

Now - it is not all that simple and these dependencies are not linear, but would not this behavior pull a break on how long a knife made if high alloy steel will be perceived as ‘sharp enough’ ? Just thinking loud


----------



## pennman (Dec 25, 2018)

Interapid101 said:


> Most desirable by who? Isn’t desirability subjective? Don’t exotic alloys come with trade offs? For folks that sharpen their own knives, it seems that wear resistance doesn’t typically top the list of desired steel attributes. Personally, I like stainless with good edge retention for pocket knives, but I prefer kitchen knives that are easily sharpened and that take a keener edge.




To sharpen and XHP knife, two different grits, takes about 3-4 minutes. To sharpen an M4 knife of the same length takes 10-12 minutes but needs to start at a lower grit so usually requires 3 grits. Yes, it takes 3-4x longer, but what’s 12 min out of your life vs. 4 minutes?


----------



## pennman (Dec 25, 2018)

Matus said:


> In one of the articles Larrin showed that toughness of steel is closely related to amount of carbides thus one may experience chipping more easily with high alloy steels. One may want to counteract that with larger sharpening angle - but that (as another article from Larrin shows) decreases the cutting ability rather quickly.
> 
> Now - it is not all that simple and these dependencies are not linear, but would not this behavior pull a break on how long a knife made if high alloy steel will be perceived as ‘sharp enough’ ? Just thinking loud




Larrin was very helpful in learning about how these toughness measurements are done. The toughness measurements were done by the charpie method which measures side impact toughness in a standard steel specimen from a swinging weight, notched or unnotched, a stress that chef knife edges are not really exposed to. And the references all state that charpie toughness measurements on hardened steel are unreliable measurements. Edge chipping on a cutting board is a torsional stress and is measured by a different method and different machinery. Those data we haven’t seen yet if they exist.


----------



## rick alen (Dec 25, 2018)

DitmasPork said:


> From a knifemaker's perspective—which I know little about—are steels like CPM S110V, m390 and hap40 much more challenging with heat treatments, etc.



I credible sounding youtube vid compared S110V from Spyderco, and Phil Wilson who is well known for his work in S110V. Lots of other PM steels represented also. Anyway the Wilson knife allegedly had twice the edge retention of the Spyde, and took top honors overall.


----------



## Larrin (Dec 25, 2018)

pennman said:


> Larrin was very helpful in learning about how these toughness measurements are done. The toughness measurements were done by the charpie method which measures side impact toughness in a standard steel specimen from a swinging weight, notched or unnotched, a stress that chef knife edges are not really exposed to. And the references all state that charpie toughness measurements on hardened steel are unreliable measurements. Edge chipping on a cutting board is a torsional stress and is measured by a different method and different machinery. Those data we haven’t seen yet if they exist.


It’s charpy and your assertions of unreliable measurements are inaccurate. Torsion toughness tests aren’t used by anyone anymore and different steels can’t even be compared with torsion toughness testing.


----------



## HRC_64 (Dec 25, 2018)

Some of the better heat treats are high tech, with vaccuum and cryo etc
can not imagine all mass-produced knives have the optimal HT for all steels,

Bark River had a similar discussion about ELMAX,
saying the windo for this steel is very small,
need to be withing a more narrow ~1 point range,
or it kinda sucks...so IMHO HT is everyhting
with certain steels.

(Just like the discussion we had around AEB-L...
but please lets not repeat that discussion here.)


----------



## Keith Sinclair (Dec 25, 2018)

Like edge retention and stainless with my yardwork spyderco M390.

For busy pro kitchen environment like carbon steel with it's ease of a couple measured strops on a S&G stone to refresh the edge. There are some stainless clad carbons that work really well in a busy kitchen. 

I do not know why some steels like SRS15, R2, AEBL, and Ginsan are easy to sharpen & deburr while other super steels take more effort to sharpen. 

I can see how a good edge retention stainless blade with a thin behind the edge grind would work in a home situation where sharpening and touchups are much less. I'm pretty spoiled with using carbon knives with great grinds at work around 25 years.


----------



## pennman (Dec 26, 2018)

Larrin said:


> It’s charpy and your assertions of unreliable measurements are inaccurate. Torsion toughness tests aren’t used by anyone anymore and different steels can’t even be compared with torsion toughness testing.




Sorry about the auto correct error of “charpy”. I’m not making any assertions. Im just using the references you gave me and quoting them directly. Are they inaccurate?


----------



## Larrin (Dec 26, 2018)

Yes, they are inaccurate. The book is referring to notched impact tests. Newer editions stopped talking about torsion toughness because the company stopped using them and transitioned to unnotched impact testing.


----------



## never mind (Dec 26, 2018)

Larrin, you are a very humble person. Thank you for your patience & generosity. Happy holidays.


----------



## pennman (Dec 26, 2018)

Larrin said:


> Yes, they are inaccurate. The book is referring to notched impact tests. Newer editions stopped talking about torsion toughness because the company stopped using them and transitioned to unnotched impact testing.


 

Yes. I understand that torsional toughness testing has not been used for a long time. What about comparing notched and unnotched impact testing? Is there a linear relationship to the results from materials tested in the notched and unnotched tests? If notched impact testing is unreliable in hardened steels, is unnotched impacting testing reliable in hardened steels?


----------



## Larrin (Dec 27, 2018)

You can see unnotched testing results on the websites of Carpenter, Bohler, and Uddeholm. Crucible uses a gentle “c-notch” which behaves similarly to unnotched specimens.


----------



## DitmasPork (Dec 27, 2018)

Larrin said:


> Chef knives also use a lot of steel compared to a folder. The extra cost of S110V or M390 along with the extra cost and time from grinding and finishing all of that highly wear resistant steel makes it less desirable to the maker. That plus what is already being done tends to be copied.



I hear what you're saying. Just out of curiosity I did a search for kitchen knife makers using M390, did find these knife makers:
http://www.bladesofthegods.com/collection-shop/ryan-clift-m390/ 
(no prices for this one)
https://bradfordknives.com/chef-series/71-chef-10.html
http://www.customsweetness.com/knife_09/

They're not as pricey as I would've thought—granted I've not heard of these makers. No intention on pulling the trigger, I love carbons.

I can see the value of a 'super steel' petty, since in my kitchen it's what tends to get used for everything from trimming fat to cutting twine and plastic.


----------



## Keith Sinclair (Dec 27, 2018)

I like a thick as a brick carbon petty as a durable do it all no worries blade. No matter how thick a carbon blade you can still make it very sharp.


----------



## tim37 (Dec 28, 2018)

Everyone is worried about thinning a "super steel" kitchen knife. Why not just order a hollow ground blade? It will be half worn out by the time you have to thin it.
Tim


----------



## Matus (Dec 28, 2018)

tim37 said:


> Everyone is worried about thinning a "super steel" kitchen knife. Why not just order a hollow ground blade? It will be half worn out by the time you have to thin it.
> Tim



First - irrespective from the grind you have ti thin behind the edge, just different grinds will mean different amount of effort necessary to get it done. Second - basically nobody makes a tall concave grind on kitchen knives - for a reason.


----------



## tim37 (Dec 28, 2018)

What is the reason?


----------



## HRC_64 (Dec 28, 2018)

tim37 said:


> What is the reason?



Kitchen knife isn't a pocket knife, they have different amounts of total surface area.
So the grind needs to be optimized differently.

10x2=20/2=~10 square inches of surface area roughly on a 10 inch chef
4x1=4/2=~2 square inches of surface area rouhly on a 4 inch pocket knife

Thats 5x multiple or 500% more important for a chef knife that 
the grind is correct, otherwise blade can (will) stick to food.

Also 5x harder to customize vs a pocketknive
if the grind sucks or blade is made of super-steel, etc

Just my $0.02


----------



## Matus (Dec 29, 2018)

tim37 said:


> What is the reason?



Cutting properties. Concave grind maximizes the contact surface between the knife and the food and thus maximizes drag/friction. And of course large concave grind is the best for food stiction.


----------



## merlijny2k (Dec 29, 2018)

Matus said:


> First - irrespective from the grind you have ti thin behind the edge, just different grinds will mean different amount of effort necessary to get it done. Second - basically nobody makes a tall concave grind on kitchen knives - for a reason.



They cán be found......
https://www.hillknives.com/hk-0008.html


----------



## Matus (Dec 29, 2018)

merlijny2k said:


> They cán be found......
> https://www.hillknives.com/hk-0008.html



Well yes - would anyone around here buy one? It probably works fine for slicing meat, but cutting an onion with that thing will be quite an experience I would guess. 

I know another one - the Nesmuk Janus knives available in Germany. I had one in hand (did not use it). The grind made no sense at all. Basically a chef knife but to compensate for the lack of mechanical strength (full concave grind) it was rather thick behind the edge. No thanks.


----------

