Hardness, wear resistance and edge retention in Kitchen knives

[blokey]

I suppose many of you have seen the drama thread, **** show aside, one thing really interest me is the discussion on how dulling mechanism work on kitchen knives. Unlike the situation in CATRA test and out door EDC stuff, most kitchen knives are used on mostly soft ingredients, many of them won't have the hard carbide to cause wear in knives, the cutting board is more likely to contribute to wear. So is kitchen knives more likely to dull from metal deformation rather than wear? If that's the case high hardness in steel might contribute more to the edge retention in kitchen knives than wear resistance of the steel. In Larrin's test, low alloy and high hardness steel like blue super and 1.2562 are very low in wear resistance compare to high alloy steel, even his own ApexUltra barely catchs up with the old 440C. But many users also reports their Aogami super laster much longer than VG10 which should have much better wear resistance. Of course this could just be placebo, but if that's actually the case, is it safe to say hardness actually contributes more in the in edge retention kitchen knife than wear resistance due to the different dulling mechanism?
Let me know what you think!

 

[blokey]

People also reporting very good edge retention with SteelPort knife, which is 52100 at 65HRC. And some of the makers report 26C3 at 65 HRC would have better edge retention than AEB-L at 62-63 HRC, which goes against the wear resistance of the respective steel.

 

[umeboshi]

I suppose many of you have seen the drama thread, **** show aside, one thing really interest me is the discussion on how dulling mechanism work on kitchen knives. Unlike the situation in CATRA test and out door EDC stuff, most kitchen knives are used on mostly soft ingredients, many of them won't have the hard carbide to cause wear in knives, the cutting board is more likely to contribute to wear. So is kitchen knives more likely to dull from metal deformation rather than wear? If that's the case high hardness in steel might contribute more to the edge retention in kitchen knives than wear resistance of the steel. In Larrin's test, low alloy and high hardness steel like blue super and 1.2562 are very low in wear resistance compare to high alloy steel, even his own ApexUltra barely catchs up with the old 440C. But many users also reports their Aogami super laster much longer than VG10 which should have much better wear resistance. Of course this could just be placebo, but if that's actually the case, is it safe to say hardness actually contributes more in the in edge retention kitchen knife than wear resistance due to the different dulling mechanism?
Let me know what you think!

Wouldn't cross-sectional geometry make a significant difference in any of these potential steel tests?

 

[blokey]

Wouldn't cross-sectional geometry make a significant difference in any of these potential steel tests?

I can't say about others, but in Larrin's case he made sure all the steel have the same geometry and angel in CATRA test.
https://knifesteelnerds.com/2020/05/01/testing-the-edge-retention-of-48-knife-steels/

 

[umeboshi]

I can't say about others, but in Larrin's case he made sure all the steel have the same geometry and angel in CATRA test.
https://knifesteelnerds.com/2020/05/01/testing-the-edge-retention-of-48-knife-steels/

I see. Based on my limited knowledge I think users reporting differences in AS having longer edge retention than VG10 would have too many variables to compare. I can see how the Larrin's tests line up tho.

 

[blokey]

I see. Based on my limited knowledge I think users reporting differences in AS having longer edge retention than VG10 would have too many variables to compare. I can see how the Larrin's tests line up tho.

That's true, and that's why I included some of experience with custom orders, I have asked steel related questions with some western makers and Japanese makers, some of them would insist high hardness carbon steel have better edge retention than stainless, for example 26c3 and aebl, also one Japanese maker told me blue and white#1 steel would have better edge retention than ginsan (19c27), different steel by same maker should have closer geometry, but of course theres variation in hand crafted items. it might just be their conventional wisdom rather than actual testing tho.

 

[HumbleHomeCook]

If you're not already familiar, I would highly encourage subscribing to Shawn Houston's YouTube and Instagram. On YT it is Big Brown Bear and TripleBHandmade on IG. He's known here as @Deadboxhero but he rarely posts here.

Shawn was the sharpener for @Larrin and has done a lot of work with him. Further, Shawn has done extensive HT, geometry, edge retention, etc. work and shares great info on the subject.

While much of what you see is using EDC knives, the principles are the same.

Geometry plays a massive role in most everything knife-performance related.

https://www.youtube.com/user/shawnhouston

Larrin also provides a ton of great info here:

https://knifesteelnerds.com/

 

[Troopah_Knives]

That's true, and that's why I included some of experience with custom orders, I have asked steel related questions with some western makers and Japanese makers, some of them would insist high hardness carbon steel have better edge retention than stainless, for example 26c3 and aebl, also one Japanese maker told me blue and white#1 steel would have better edge retention than ginsan (19c27), different steel by same maker should have closer geometry, but of course theres variation in hand crafted items. it might just be their conventional wisdom rather than actual testing tho.

I really think specific examples like this are based on conventional wisdom and tradition rather than testing. However, I don't think your main point is invalid. As I see it there are 3 forms of dulling:

1. Microchipping
2. Rolling
3. Abrasion

and CATRA is only a test of the third. There certainly could be cases where abrasion is not the dominant form of wear and thus your edge retention will not be predicted by the CATRA test. Identifying the dominant form of wear in your knives can help with geometry and material selection for future work/purchases. However, it can be somewhat hard to identify which is which as all occur at a very small scale and can interact with each other. For example, if you have a knife with rolling dominant dulling the edge may initially roll but the now fatigued steel will then chip off. So upon examining the edge you could easily come to the conclusion that microchipping is the dominant form of wear. So the real question in my opinion is not if there are cases where hardness could be having a larger contribution but rather when.

Unlike the situation in CATRA test and out door EDC stuff, most kitchen knives are used on mostly soft ingredients, many of them won't have the hard carbide to cause wear in knives

Silica is the most common abrasive found in food. I don't see why CATRA wouldn't be a valid wear resistance test for food.

 

[esoo]

For carbon knives, the acids in the food dull the edge. To see this quantitatively, sharpen a knife, patina it in lemon juice and then test the edge. Everytime I've done this it is duller than before. This seems it occur regardless of the HRC so it has to do with the composition of the steel.

Do I understand the exact mechanics of what is happening? No. Would the same thing happen to stainless (leave it lemon juice for thirty minutes and see how sharp it is afterwards)? Not a clue.

 

[Benuser]

For carbon knives, the acids in the food dull the edge. To see this quantitatively, sharpen a knife, patina it in lemon juice and then test the edge. Everytime I've done this it is duller than before. This seems it occur regardless of the HRC so it has to do with the composition of the steel.

Do I understand the exact mechanics of what is happening? No. Would the same thing happen to stainless (leave it lemon juice for thirty minutes and see how sharp it is afterwards)? Not a clue.

It will — to a lesser degree. Can I explain the mechanism: no. Just repeating what others have said about microcorrosion. It's good practice to treat your stainless as if they were carbons: clean at least the edge as soon as you can.

 

[coxhaus]

I have a MAC Pro knife and it seemed to have dulled after cutting a bag of limes over a couple of weeks. Using it in my kitchen it seemed to work a lot like my Henckels 4-star knives until we started cutting limes. It dulled faster than my Henckels 4-star knives. This is my impression of what happened but no scientific proof to back it up.

I was my first buy into a Japanese knives sight unseen. I heard good things about MAC knives. It turned out the handle was too small for my hand so I don't really use it and I will get rid of it at some point.

 

[Larrin]

For carbon knives, the acids in the food dull the edge. To see this quantitatively, sharpen a knife, patina it in lemon juice and then test the edge. Everytime I've done this it is duller than before. This seems it occur regardless of the HRC so it has to do with the composition of the steel.

Do I understand the exact mechanics of what is happening? No. Would the same thing happen to stainless (leave it lemon juice for thirty minutes and see how sharp it is afterwards)? Not a clue.

https://knifesteelnerds.com/2019/01/21/does-acidic-food-affect-edge-retention/

 

[coxhaus]

All can say is the MAC knife would not cut tomatoes after using it for the limes.

 

[superworrier]

I really think specific examples like this are based on conventional wisdom and tradition rather than testing. However, I don't think your main point is invalid. As I see it there are 3 forms of dulling:

1. Microchipping
2. Rolling
3. Abrasion

and CATRA is only a test of the third. There certainly could be cases where abrasion is not the dominant form of wear and thus your edge retention will not be predicted by the CATRA test. Identifying the dominant form of wear in your knives can help with geometry and material selection for future work/purchases. However, it can be somewhat hard to identify which is which as all occur at a very small scale and can interact with each other. For example, if you have a knife with rolling dominant dulling the edge may initially roll but the now fatigued steel will then chip off. So upon examining the edge you could easily come to the conclusion that microchipping is the dominant form of wear. So the real question in my opinion is not if there are cases where hardness could be having a larger contribution but rather when.



Silica is the most common abrasive found in food. I don't see why CATRA wouldn't be a valid wear resistance test for food.

It seems like this doesn’t include deformation? Which was mentioned in Larrin’s MagnaCut video.

Also it would be a valid wear resistance test but maybe not predictive of edge retention if wear only contributes a little bit to dulling in kitchen use cases. But I may just be talking nonsense here.

Curious what Larrin has to say (maybe even an article)

 

[esoo]

https://knifesteelnerds.com/2019/01/21/does-acidic-food-affect-edge-retention/

Aside from the fact that I would've soaked the blade, this is basically the test that I was thinking of.

 

[Troopah_Knives]

It seems like this doesn’t include deformation? Which was mentioned in Larrin’s MagnaCut video.

Also it would be a valid wear resistance test but maybe not predictive of edge retention if wear only contributes a little bit to dulling in kitchen use cases. But I may just be talking nonsense here.

Curious what Larrin has to say (maybe even an article)

deformation = rolling.

My only point about CATRA was that it is a valid test of wear resistance, not that it is predictive of all dulling behavior.

 

[Barmoley]

It seems like this doesn’t include deformation? Which was mentioned in Larrin’s MagnaCut video.

Also it would be a valid wear resistance test but maybe not predictive of edge retention if wear only contributes a little bit to dulling in kitchen use cases. But I may just be talking nonsense here.

Curious what Larrin has to say (maybe even an article)

Rolling and deformation are the same phenomena it is all deformation.

 

[superworrier]

I guess the other big issue is the definition of dull which matters because presumably the rate of dulling is different at different sharpness levels.

 

[blokey]

I really think specific examples like this are based on conventional wisdom and tradition rather than testing. However, I don't think your main point is invalid. As I see it there are 3 forms of dulling:

1. Microchipping
2. Rolling
3. Abrasion

and CATRA is only a test of the third. There certainly could be cases where abrasion is not the dominant form of wear and thus your edge retention will not be predicted by the CATRA test. Identifying the dominant form of wear in your knives can help with geometry and material selection for future work/purchases. However, it can be somewhat hard to identify which is which as all occur at a very small scale and can interact with each other. For example, if you have a knife with rolling dominant dulling the edge may initially roll but the now fatigued steel will then chip off. So upon examining the edge you could easily come to the conclusion that microchipping is the dominant form of wear. So the real question in my opinion is not if there are cases where hardness could be having a larger contribution but rather when.



Silica is the most common abrasive found in food. I don't see why CATRA wouldn't be a valid wear resistance test for food.

Thank you, this is definitely worth investigating, maybe instead of cardboard in CATRA we can do carrot planks lol

 

[superworrier]

Thank you, this is definitely worth investigating, maybe instead of cardboard in CATRA we can do carrot planks lol

I seem to recall someone doing a similar sort of test to test cutting boards: hitting a knife against different types of cutting boards X times (I don't know how well it was designed) to test how different cutting boards dulled edges. Here is an old thread about one Cutting board effect on sharpness although I kind of recall someone like ATK or Wirecutter also doing a similar test, but I cannot find it

 

[blokey]

I seem to recall someone doing a similar sort of test to test cutting boards: hitting a knife against different types of cutting boards X times (I don't know how well it was designed) to test how different cutting boards dulled edges. Here is an old thread about one Cutting board effect on sharpness although I kind of recall someone like ATK or Wirecutter also doing a similar test, but I cannot find it

If you mean this ATK test I wouldn't call it good...

 

[superworrier]

If you mean this ATK test I wouldn't call it good...

I'm thinking of one about cutting boards, but it might be the one in the forum link I mentioned.

 

[Heckel7302]

I'm thinking of one about cutting boards, but it might be the one in the forum link I mentioned.

this one?

https://www.seriouseats.com/the-best-plastic-cutting-boards