Chippy Knives and Toughness: How Low Can You Go?

[Troopah_Knives]

I and probably many of you have noticed that edge performance and chippiness are characteristics fundamentally at odds. You can thin a knife down until it is extremely thin behind the edge and it will cut beautifully but the resulting edge will just be too delicate to use. On the maker end, you can heat treat a blade to higher and higher hardness but at some point, you need so much thickness behind the edge that the knife just doesn't cut well anymore. Over the past couple of years, @Larrin has been doing amazing work testing the toughness (a measure of strength and ductility) of knife steels but as with all good scientific data he has controlled for as many variables as possible. I am interested in trying to link that well-controlled data to actual kitchen knives where there are much fewer controls. In order to do that, we have to make some assumptions, institute some controls, and state some things we can't control.

1. Let's only talk about chef's knives and gyutos with edges sharpened in the 15dps range (does need to be exact just nothing totally insane like 30dps).
2. We can't be too picky and are going to have to largely ignore differences in grinds. This may actually be more valid than it initially seems. Most chips I've seen don't extend very far into the edge (1/8" or so) and over that distance, there are substantial similarities between blades even those with different grinds.
3. We can't be too picky (pt2) we can't control for people's different cutting styles.

So here's the question: Is it possible to establish a minimum toughness level for the average user before a knife is considered chippy?

Here are my thoughts: I think if I could get enough people on board this could be possible. In order to do so, I would need people to report knives they thought were chippy, the steel, and the approximate HT hardness. I could then compare that data to the hardness toughness charts to find an approximate toughness of that steel. Finally, I would plot the reported hardness vs the toughness and we would get a chart with a region of steels people thought were chippy. Is this fully valid, ready to publish science? Not even a little. Do I think it's worth a try? Yes!

What do you all think? Is this a project worth going forward with? If so what do you think would be the best way to collect data? Do you have any suggestions or criticisms?

 

[HumbleHomeCook]

There are three prime variables in knife performance:

1. Steel Composition
2. Heat Treat
3. Geometry

I think @Deadboxhero's current work on Spyderco's might have me thinking that perhaps this should be expanded to four variables to include the abrasive but for now, I'm going with three.

It is, in my opinion, impossible to glean any meaningful, communally applicable data, without controlling all three. You simply can't dismiss the geometry and here, when testing limits, subtle changes matter.

You'd also have to know the hardness of the individual blades.

And this doesn't even consider use-case.

 

[Troopah_Knives]

There are three prime variables in knife performance:

1. Steel Composition
2. Heat Treat
3. Geometry

I think @Deadboxhero's current work on Spyderco's would might have me thinking that perhaps this should be expanded to four variables to include the abrasive but for now, I'm going with three.

It is, in my opinion, impossible to glean any meaningful, communally applicable data, without controlling all three. You simply can't dismiss the geometry and here, when testing limits, subtle change matters.

You'd also have to know the hardness of the individual blades.

And this doesn't even consider use-case.

I think you are definitely right to some extent. I would expect any data collected to be very noisy. Nevertheless, even noisy data can be useful. For example, earlier CATRA data didn't control for geometry which introduced a significant amount of noise to the data set @Larrin compiled in his article "Which Steel Has the Best Edge Retention? Part 1" but he was still able to show some interesting correlations with that data. I'm not expecting to get a nice clean correlation out of this rather more of a probability scatter. There may be a couple of people who have outliers in terms of their use but we may be able to show some sort of group consensus given enough data points.

 

[Barmoley]

I think most tend to disregard how huge of a role geometry plays. I also suspect that most who claim that they sharpen at a certain angle or that their edges are of a certain thickness are mistaken. Without proper tools it is very hard to be sure and if we can't control geometry I am afraid the conclusions will be very misleading. Most here sharpen free hand without any angle measurements and are just guessing at an angle. Both Larrin and Shawn as well as others have shown how big of a difference relatively small changes of an angle make. Take a look at Shawn's study like @HumbleHomeCook suggested, if you don't know geometry and hardness it seems pretty impossible to get any good results. You have to remember that if you are relying on what people tell you about hardness and geometry you are relying on pure guesses. I also think you are overlooking how big of a difference cutting technique makes, lateral stress will cause chipping and technique controls lateral stress to a very high degree. It would be one thing if the same person cut with all the knives, but comparing different knives with unknown geometry and hardness used by different people on different ingredients.....

 

[HumbleHomeCook]

I'm familiar with Dr. Thomas' work but if I'm understanding what you correctly, you're idea is for users to report results correct?

If so, there are just way too many variables to be meaningful. I mean you're into what is being cut, how it is cut, on what is it cut, etc.

 

[rmrf]

TL;DR: I think cutting style, what you cut, and knife geometry are the dominant factors for a survey like this. I'll be surprised if you can get meaningful trends (not overfitting) for chipping vs heat treatment or hardness or other material properties.

I think cutting styles and what you cut matter a lot so you'd have to control for that. For instance, I don't eat hard squash like butternut or acorn so a knife that can tolerate cutting acorn squash wouldn't be useful to me. So, I thin my knives more aggressively than people who eat a lot of squash. That said, I've never chipped a knife. Once, I was cutting through parm with a gengetsu and I twisted wrong and the edge came out looking a little bent but that was it.

I suspect asking for hardness will also be difficult. I don't know the hardness of any of my knives to +/- 1 precision. I would be relying on vendors to tell me and who knows how accurate that is.

Also, I'd be very very surprised if geometry is not a dominant factor. I mean, I've heard that people fix the "chippy" problem with their knives with micro bevels or sharpening at a different angle or things like that. I'm trying the opposite (thinning until the knife gets chippy, then backing off, but I've been lazy so I haven't gotten it to the chippy point yet).

I should also note that I have gotten micro chips (things that come out in a single sharpening) from a cheap (soft) dexter stainless knife that I use for hacking into pizza. Its sharpened thicker than any of my other knives. Does this mean that soft stainless is more chippy than white, blue, skd, or sg2? Or is it that cutting hard cracker pizza dough by slamming a knife into it and putting half my bodyweight onto the knife is a more destructive test than cutting potatoes or garlic or kale?

 

[HumbleHomeCook]

Let me come back to say, that I appreciate the enthusiasm. I just think the variables are too many to overcome.

Now, if you're making knives in steels that aren't common in the kitchen cutlery world, can you channel this into maybe doing some of your own testing on those steels?

 

[Troopah_Knives]

I think most tend to disregard how huge of a role geometry plays. I also suspect that most who claim that they sharpen at a certain angle or that their edges are of a certain thickness are mistaken. Without proper tools it is very hard to be sure and if we can't control geometry I am afraid the conclusions will be very misleading. Most here sharpen free hand without any angle measurements and are just guessing at an angle. Both Larrin and Shawn as well as others have shown how big of a difference relatively small changes of an angle make. Take a look at Shawn's study like @HumbleHomeCook suggested, if you don't know geometry and hardness it seems pretty impossible to get any good results. You have to remember that if you are relying on what people tell you about hardness and geometry you are relying on pure guesses. I also think you are overlooking how big of a difference cutting technique makes, lateral stress will cause chipping and technique controls lateral stress to a very high degree. It would be one thing if the same person cut with all the knives, but comparing different knives with unknown geometry and hardness used by different people on different ingredients.....

Yeah, I've read through that study a couple of times very interesting work. At least on the topic of hardness, many manufacturers will report it and a variance of 1-2 HRC points would add noise but is not necessarily insurmountable. Knives of unknown hardness would not be used.

I agree that technology has a huge effect on how lateral stresses are applied to blades. I guess my question is this: would those differences make the data too noisy to be useful? And I don't see a way to know the answer to that question without trying it.

To explain it better here's roughly what I would expect to see. At some toughness level lots of people will report having chippy blades, doesn't matter what geometry or cutting technique. But as we move to a higher level of toughness more robust geometry and people with more gentle techniques will stop having issues thus there will be fewer data points. And at some level of toughness, there will no longer be any reports of chippy blades because you could drop it out your 10th story window and it would only bend.

 

[Troopah_Knives]

TL;DR: I think cutting style, what you cut, and knife geometry are the dominant factors for a survey like this. I'll be surprised if you can get meaningful trends (not overfitting) for chipping vs heat treatment or hardness or other material properties.

I think cutting styles and what you cut matter a lot so you'd have to control for that. For instance, I don't eat hard squash like butternut or acorn so a knife that can tolerate cutting acorn squash wouldn't be useful to me. So, I thin my knives more aggressively than people who eat a lot of squash. That said, I've never chipped a knife. Once, I was cutting through parm with a gengetsu and I twisted wrong and the edge came out looking a little bent but that was it.

I suspect asking for hardness will also be difficult. I don't know the hardness of any of my knives to +/- 1 precision. I would be relying on vendors to tell me and who knows how accurate that is.

Also, I'd be very very surprised if geometry is not a dominant factor. I mean, I've heard that people fix the "chippy" problem with their knives with micro bevels or sharpening at a different angle or things like that. I'm trying the opposite (thinning until the knife gets chippy, then backing off, but I've been lazy so I haven't gotten it to the chippy point yet).

I should also note that I have gotten micro chips (things that come out in a single sharpening) from a cheap (soft) dexter stainless knife that I use for hacking into pizza. Its sharpened thicker than any of my other knives. Does this mean that soft stainless is more chippy than white, blue, skd, or sg2? Or is it that cutting hard cracker pizza dough by slamming a knife into it and putting half my bodyweight onto the knife is a more destructive test than cutting potatoes or garlic or kale?

I addressed most of the above in previous replies as best I could. I too am not satisfied that this is a perfect or even good way of testing this I just can't think of any other way.

On the topic of microchips: No those would not be counted as microchipping is more of a form of fatigue wear and likely is controlled by a number of different factors, such as hardness, carbide size, heat fatigue etc, not just toughness although not a ton of study on it had been done.

 

[HumbleHomeCook]

Yeah, I've read through that study a couple of times very interesting work. At least on the topic of hardness, many manufacturers will report it and a variance of 1-2 HRC points would add noise but is not necessarily insurmountable. Knives of unknown hardness would not be used.

I agree that technology has a huge effect on how lateral stresses are applied to blades. I guess my question is this: would those differences make the data too noisy to be useful? And I don't see a way to know the answer to that question without trying it.

To explain it better here's roughly what I would expect to see. At some toughness level lots of people will report having chippy blades, doesn't matter what geometry or cutting technique. But as we move to a higher level of toughness more robust geometry and people with more gentle techniques will stop having issues thus there will be fewer data points. And at some level of toughness, there will no longer be any reports of chippy blades because you could drop it out your 10th story window and it would only bend.

Read your last paragraph again. The only way to get there is to have soft steels sharpened like an axe. You can't get around geometry and use.

 

[Troopah_Knives]

Let me come back to say, that I appreciate the enthusiasm. I just think the variables too many to overcome.

Now, if you're making knives in steels that aren't common in the kitchen cutlery world, can you channel this into maybe doing some of your own testing on those steels?

Certainly, I suspected such a problem going in, if I were sure that this was the way to go I would just do it. Posted the idea here so as not to waste time.

I'm currently working on hardness and toughness testing of pm-M4 and T-15 Datasheet HTs, with the low-temperature temper and cryo commonly used on steels like CPM-10v. For some reason, someone thought it was a good idea to give me access to a lab so I've got all the fun toys.

 

[Delat]

There’s a few guys on the forum who take both their edges and BTE thickness to increasingly low angles and then back off when they get chipping. But they’re playing with both edge angle and geometry.

I would guess most of here are perfectly happy to avoid chipping in the first place vs seeking it out.

My edges are all 30 degrees inclusive and I don’t really have any chipping to speak of. My knives are almost all AS and R2, probably in the 61-63 HRC range. But I’d note that I use that very conservative 30 degrees to avoid chipping in the first place. I do measure my angles so they’re spot on at 15 dps +/- .3 degrees. I probably would be more worried about chipping if I got a knife that was over 65 HRC, which might be a reason I don’t own any

Anyway there’s a thread on chipped edges - you might want to pop over there and ask about the steel and HRC of the knives that chipped.
https://www.kitchenknifeforums.com/threads/the-chipped-knife-thread.57451/page-2#post-879007

 

[HumbleHomeCook]

Certainly, I suspected such a problem going in, if I were sure that this was the way to go I would just do it. Posted the idea here so as not to waste time.

I'm currently working on hardness and toughness testing of pm-M4 and T-15 Datasheet HTs, with the low-temperature temper and cryo commonly used on steels like CPM-10v. For some reason, someone thought it was a good idea to give me access to a lab so I've got all the fun toys.

In literature, they say write about what you know.

 

[Barmoley]

Yeah, I've read through that study a couple of times very interesting work. At least on the topic of hardness, many manufacturers will report it and a variance of 1-2 HRC points would add noise but is not necessarily insurmountable. Knives of unknown hardness would not be used.

I agree that technology has a huge effect on how lateral stresses are applied to blades. I guess my question is this: would those differences make the data too noisy to be useful? And I don't see a way to know the answer to that question without trying it.

To explain it better here's roughly what I would expect to see. At some toughness level lots of people will report having chippy blades, doesn't matter what geometry or cutting technique. But as we move to a higher level of toughness more robust geometry and people with more gentle techniques will stop having issues thus there will be fewer data points. And at some level of toughness, there will no longer be any reports of chippy blades because you could drop it out your 10th story window and it would only bend.

You can certainly try. Hardness reported by manufacturers is very suspect. When they say 62 HRC it can really be 60-64 as an example, that is a huge difference, but lets say it is not that large and is somewhat useful. Geometry will be all over the place. In the aforementioned study a blade had multiple angles depending on where on the edge one measured, how do you account for that? That in addition to no one really knowing what the angles are in the first place. The technique difference are also larger than you give them credit, there is no gentle vs harsh for everyone it is all relative, you might apply less force to a knife but apply more lateral stress vs someone applying more force but cutting straighter. Look at our discussion of VG10 and Shun specifically, some people never chipped one and some can't stop them from chipping. This is just one steel and one manufacturer and even there it is not clear what is going on.

 

[Barmoley]

There’s a few guys on the forum who take both their edges and BTE thickness to increasingly low angles and then back off when they get chipping. But they’re playing with both edge angle and geometry.

I would guess most of here are perfectly happy to avoid chipping in the first place vs seeking it out.

My edges are all 30 degrees inclusive and I don’t really have any chipping to speak of. My knives are almost all AS and R2, probably in the 61-63 HRC range. But I’d note that I use that very conservative 30 degrees to avoid chipping in the first place. I do measure my angles so they’re spot on at 15 dps +/- .3 degrees. I probably would be more worried about chipping if I got a knife that was over 65 HRC, which might be a reason I don’t own any

Anyway there’s a thread on chipped edges - you might want to pop over there and ask about the steel and HRC of the knives that chipped.
https://www.kitchenknifeforums.com/threads/the-chipped-knife-thread.57451/page-2#post-879007

How do you measure your edge angle to such precision?

 

[Delat]

How do you measure your edge angle to such precision?

It makes for very slow sharpening but I rarely need to do much anyway. It took me months to get my wobble down to +/- .3
https://www.kitchenknifeforums.com/threads/gizmo-says-i-suck.54409/

 

[Troopah_Knives]

You can certainly try. Hardness reported by manufacturers is very suspect. When they say 62 HRC it can really be 60-64 as an example, that is a huge difference, but lets say it is not that large and is somewhat useful. Geometry will be all over the place. In the aforementioned study a blade had multiple angles depending on where on the edge one measured, how do you account for that? That in addition to no one really knowing what the angles are in the first place. The technique difference are also larger than you give them credit, there is no gentle vs harsh for everyone it is all relative, you might apply less force to a knife but apply more lateral stress vs someone applying more force but cutting straighter. Look at our discussion of VG10 and Shun specifically, some people never chipped one and some can't stop them from chipping. This is just one steel and one manufacturer and even there it is not clear what is going on.

I'm certainly not saying that I can account for most of those factors. This would be chippiness defined based on probability.
The basic idea of how to account for technique is this: If you give 100 people 2 knives and 70% chip knife one and 10% chip knife two you can say with some certainty that knife one is more prone to chipping. Then you could apply this to the other factors by giving those same people 100 knives in two steels if 20% of steel A knives chip and 60% of steel B knives chippy you can say that steel B with that HT is more chippy than steel A with its HT. Then you can go a layer further to look at the steels with different HT. Polling a large number of people would be somewhat similar to running a study like that. The point is if you can collect a lot of data you can start to account for these things. The more I think about it the more I think you are right that it would be very hard to get anything useful out of it but I really think that's due to an inability to collect data. If only we could collect this data from every knife on earth.

 

[stringer]

All of my knives have chips. That's how I know they are thin enough.

 

[Luftmensch]

So here's the question: Is it possible to establish a minimum toughness level for the average user before a knife is considered chippy?

I have argued a similar line in the past. I realise this is *my* personal preference/opinion... but surely beyond some threshold of toughness you are needlessly sacrificing edge retention.

Knife steel nerds is well presented and fairly objective. There is a sprinkling of editorial language that betrays Larrin's preferences. Mostly this is when Larrin participates in forums. The first thing to note is that @Larrin writes about steels from a fairly general perspective. His writing is not specific to kitchen knives. It is worth acknowledging that. Optimising a machete for clearing scrub... or a knife for salt water diving... isnt really the same as optimising a kitchen knife. So you have to ask... which parameters are useful in the kitchen?

I think it is fair to say Larrin is on record stating a preference for 'well balanced steels'. There is absolutely nothing wrong with this! It will produce an elegant, well rounded steel. But I believe this is where some of Larrin's opinions/editorial language is adopted uncritically by kitchen knife nerds. Just to be clear, this isn't Larrin's fault... it is one of the hazards of being in the public sphere!

@Troopah_Knives; like you, the balance of parameters for kitchen knives that interests *me* is the minimum amount of toughness with some safety factor. This will allow you to increase your hardness/edge retention. In doing this, you would need to know the toughness that will satisfy your edge geometry and use in the kitchen. Someone doing line prep by the bushel on an unforgiving cutting board is likely to need more toughness than a home cook.


How much toughness is enough in the kitchen? Who knows . I would like to know a good benchmark number. But i suspect useful numbers are lower than people might expect...

Let me contribute a controversial data point by way of anecdotal example: Gihei Zuika ZDP-189. Marketing material says it is heat treated to ~65HRC. Reading off Larrin's results... the toughness might be around 3 or 4 ft-lbs. It is a poorly balanced steel. In fact, the toughness is lower than most of the steels Larrin tested. I have thinned my ZDP knives a bit... who knows what the edge angles are?! Are they chippy?? Sort of yes and sort of no... I had problems with the factory edge. This is complete speculation... but I wonder if the very edge (0.1mm) overheated during grinding? Very early on, I had microchips. Since grinding that steel away, I have not. Maybe I increased the edge angle. Either way, while I dont baby my knives, I know they can only take so much abuse. I dont do obviously reckless things like trying to cut through bone or frozen foods. Yet I am happy to cut things like squash (which often results in heavy board contact). With the smallest amount of mindfulness and technique... I do not feel limited by their low toughness. But perhaps it is on the edge of acceptable??

Maybe I am overestimating the amount of aversion to ZDP-189 in some parts of the community? And I certainly dont mean to be an apologist for the steel (it is good, I am not sure it is 'super')! But I think it is a good example of how a very low toughness steel can be adequate (if not, great) in the kitchen. Is more toughness better? Maybe... probably... but it depends what you are trading off...

 

[Troopah_Knives]

@Luftmensch you bring up a good point about his work not being kitchen knife specific and I think this ties a bit into the idea of well-balanced steel. I work entirely with kitchen knives so well-balanced steel doesn't necessarily mean the same thing to me as it would to someone who makes bushcraft knives. If anything I think what interests me most about toughness in kitchen knives is the extent to which it's not necessary. Sure your ZDP-189 might have 3-4 ft-lb toughness which is low considered to other steels but taken in the context of kitchen knives. That really hardly even an outlier. Plenty of people use white paper and blue paper steel in the 64rc range where the toughness is really negligibly different from ZDP-189. That said the steel does have other issues although if those don't bother more power to you! Once I stopped paying so much attention to hardness toughness balancing I start looking into different topics such as different forms of edge failure and that's where you can start to understand some of the subtleties of different steels character.

But before I get any further off-topic I think the largest benefit of toughness testing is how useful it is in comparing for personal preference. For example, if you have no problem handling ZDP-189 at 65rc there is really no reason why you should find Z-Max at 68RC hard to handle (assuming a similar grind). I personally frequently use all his data when selecting new steels to try and get a sense of where to push the grind.

Finally to tie it back to the start of what you said at the start of your post. In some ways, I think kitchen knives are the best place to apply the threshold toughness concept but mostly when it comes to steel selection not necessarily heat treatments (but sometimes those too it all depends). While as mentioned in this thread it is very hard (maybe impossible) to determine a lower toughness range for everyone. I certainly have a good idea of what that number is for my work especially when I know the user.

 

[branwell]

Do you have any suggestions or criticisms?

Cool idea but not possible as you lay it out.

There are a number of problems ranging from manufactures publishing inaccurate hardness numbers, to zero information on how they did their heat treat, normalizing temp ( if any ), grain reduction, did they ramp to what austenitizing temp and what was their dwell? Did they kick of from perlite, spheroidized etc. How did they quench? Temper strat?

All of that plays hugely in the performance of the steel so you would have no choice but to make or have a batch of knives made where you could quantify / control the variables and then test.

Even if you where to say, well lets not be anal about it and just get some idea. Again, I don't think you could get far. I've seen great AS and poor AS. I've seen great 52100 and poor 52100. Great AEBL and horrible AEBL. Same for R2, VG10 etc.

What you could possibly do is say X company's knives appear to be chippy. Or Y companies knives tend to be bullet proof.

I like the idea but dont think its feasible to do with any accuracy.

 

[Luftmensch]

Plenty of people use white paper and blue paper steel in the 64rc range where the toughness is really negligibly different from ZDP-189.

Anyway there’s a thread on chipped edges - you might want to pop over there and ask about the steel and HRC of the knives that chipped.
https://www.kitchenknifeforums.com/threads/the-chipped-knife-thread.57451/page-2#post-879007

By way of coincidence... I was the person who started the thread @Delat referenced!

I dropped my knife on to tiles... I am disappointed it the tip chipped off but I am not surprised. Unknown steel composition (Shigefusa spicey white...).... unknown HRC - I suspect approaching mid 60's.

If you are accident prone, a tougher steel would help make tips and heels more resilient!

if you have no problem handling ZDP-189 at 65rc there is really no reason why you should find Z-Max at 68RC hard to handle (assuming a similar grind).

Absolutely! I would love to try some of those more exotic steels. I am just too lazy and conservative to sit on a waiting list. When I have these fancies, I like to act while I have the cash flow and interest.

I think kitchen knives are the best place to apply the threshold toughness concept but mostly when it comes to steel selection not necessarily heat treatments

I agree! Although the threshold may imply there are limitations in the practical heat treatments you can explore.

 

[Barmoley]

I'm certainly not saying that I can account for most of those factors. This would be chippiness defined based on probability.
The basic idea of how to account for technique is this: If you give 100 people 2 knives and 70% chip knife one and 10% chip knife two you can say with some certainty that knife one is more prone to chipping. Then you could apply this to the other factors by giving those same people 100 knives in two steels if 20% of steel A knives chip and 60% of steel B knives chippy you can say that steel B with that HT is more chippy than steel A with its HT. Then you can go a layer further to look at the steels with different HT. Polling a large number of people would be somewhat similar to running a study like that. The point is if you can collect a lot of data you can start to account for these things. The more I think about it the more I think you are right that it would be very hard to get anything useful out of it but I really think that's due to an inability to collect data. If only we could collect this data from every knife on earth.

I certainly don't want to discourage you. I understand what you are trying to do and if you collect enough data one could argue that given a symetric, normal like distribution the geometry or hardness differences could go away. The problem I see is the quality of the data. Since you are relying on users to give you geometry and other numbers you are betting on normal like distribution. I suspect that it is not. I suspect that people that don't chip their blades in relatively low toughness steels underestimate their geometry. Basically, they believe their angles are smaller and edges are thinner than reality.

Since, you are a knife maker and work with very cool steels I would think that you could get better data by taking 2 blades in tough and brittle steels to the limit and figure out the toughness threshold. @stringer does something similar he goes as thin as possible and then backs off in a way finding the steepest and thinnest for that steel in his use.

The thing is that most of the popular kitchen knife steels have relatively low toughness and yet work fine which might mean that the geometries compensate for the steel or that toughness is not that important in kitchen knives. It is most likely a combination of the two to some degree.

 

[ModRQC]

In reading OP I had only one thought: this would invariably lead into a region where even same steels reputed of same hardness, from even the same or a different maker, would get you the same grey zone you are trying to confront here: there would be 65RC super thin W#1 units (for example) that would be claimed the same unchippy - or chippy - as a regular W#1 HT with much more average thickness BTE. Very same knives would hit very different ballparks from users reports.

The most liable thing you would find is what we already somewhat know: makers. You'd hear a lot about Yoshikanes, Takamuras or whatever makers already reputed to get knives in a dangerous region for steel/grind/dps etc etc etc.

Recently got a Wakui that was "zingy" as hell OOTB. You basically couldn't do much of any regular cutting with it that wouldn't either zing or have that very suspect typical "clicking" sound in various techniques. Another Wakui is tough as nail. Yet the zingy one is White #2, the tough one A#2, and technically A#2 should be a little more frail. And then again, this a Wakui Migaki W#2. Looking at the grind of a Wakui Nashiji W#2, it's much more akin to my A#2 unit and I'm fairly certain wouldn't exhibit the same traits as my Migaki.

There you already know what's wrong with trying this just within what I said:

I don't claim having perfect technique, but 99% knives either OOTB or as I thinned them do not behave like that at all and I take/took much less care cutting with them than I'll do a zingy edge. But what do I know and how would you trust me to be true than my Mabs W#1 is about as thin, much harder, and just about impossible to chip where it stands now.

But then again... micro-chipping? Perhaps the Mabs does. I THINK it's proven to me that it doesn't degrade nowhere near as fast as you'd expect an edge prone to micro-chipping. But what do I know and how would you trust me to be true?

On another train of thoughts, I agree most damages reported *tend* to occur not far up the edge. But you can't dismiss geometry even out of those cases, because geometry to many levels dictate how a very same user will use a knife. Wide bevels, they very well may be using noticeably more momentum than with lasers. I don't care how good and rugged the user is: a laser reports differently to a wide bevel in cutting, and it's only natural that one adjusts AT LEAST momentum, probably a few more parameters of use, so that they make sense with the knife. I can't believe anyone so good or rugged with knives wouldn't do that as it seemed to be a pretty natural adaptation to the noobful me from the start.

 

[ModRQC]

... I can't believe anyone so good or rugged with knives wouldn't do that as it seemed to be a pretty natural adaptation to the noobful me from the start.

Yet if they DO, it'd be another thing to entirely throw off the stats you'd be trying to make sense of.

 

[Luftmensch]

If I had the resources and time to quantify this, I would establish the following experiment:

I call it the "Luftmensch kitchen impact test"

As you can see... it is not too different from other impact tests. It would be an easy jig to make. It differs in that it is a first-order approximation of what forces a kitchen knife might be subjected to (in the worst case). You could standardise all the parameters so that others could replicate the experiment. Note that many of the parameters don't really matter - particularly if you are simply testing for a pass or fail result. The weight of the hammer... the length of the arm... the height at which you drop it... choose rational parameters - something that exaggerates a heavy hand in the kitchen. The cutting material could be any analogue... bamboo... a plastic rod... The cutting board doesnt need to be HDPE... but why not?? So long as you record these parameters and use consistent materials (particularly the cutting material), it will have some level of repeatability.

Methodology:

• Make testing blades with the same geometry (e.g. standard 15° per side).
  • Vary the heat treatment as many times as you can bother (e.g. HRC in increments of 2 from 58 to 68)
  • Test the hardness and toughness of each heat treatment in the lab
• For each heat treatment:
  • Test to see if the blade fails after one blow.
  • Test to see if the blade fails after multiple blows (10?)

Since you tested the hardness and toughness of each heat treatment in the lab, you can now correlate your pass/fail results with some more precise measurements. The results ought to illuminate a toughness where fracture occurs. If you made the test aggressive, if might be a reasonable approximation for a worst-case scenario. Speaking in generalities (ignoring second, third order effects... etc), you might be able to argue that this threshold is a good baseline that applies (approximately) to any steel composition at the given geometry - I could be wrong about this...

If you wanted to be more analytical, you could ask additional questions such as... How many blows until failure? How big is the failure (area/depth)?


Publish the results! Then sit back and watch people in the community complain about how it is not an accurate representation of ingredient preparation. Or how the hammer is nothing like a human fist... or how real people dont use HDPE cutting boards?? Or how it doesnt measure edge retention...

 

[Troopah_Knives]

the geometry or hardness differences could go away. The problem I see is the quality of the data. Since you are relying on users to give you geometry and other numbers you are betting on normal like distribution. I suspect that it is not. I suspect that people that don't chip their blades in relatively low

I see what you're saying and I think you're right. This isn't the way forward too much data be needed for even something approaching useful results.

 

[Troopah_Knives]

@Luftmensch your tests look interesting. It might help people more easily understand the actual working performance of the steel in real work. I think however you would have to define failure as a crack or an edge deformation. So the resulting test would actually be more of a strength+fracture resistance test rather then a toughness test as lower strength higher ductility steels would steel perform poorly. In that way, it would be different from many current impact tests where the sample is always pushed past its ultimate tensile stress. Instead, here you would reach yield stress in ductile steels and UTS in more brittle steels. I'll certainly keep that idea in the back of my brain!

 

[Troopah_Knives]

@ModRQC I know your point with manufacturers the original idea was that with enough data you could look past those trends but I don't think there is any way to gather enough accurate data.

On the topic of microchipping: The term is slightly muddy. I and many other makers use it to refer to fatigue chipping which you can commonly see on high carbide volume steels and doesn't make any sorts of noises. It seems you are using the term to refer to chips that occur when the strength of the material at the edge is exceeded causing a fracture at the edge. In both cases, it could be that chipping on such a small scale is not dominated by toughness as it is on a large scale but rather based on hardness and carbide volumes (This could be an area for some interesting research especially for kitchen knives).

 

[BoSharpens]

Troopah_Knives noted "Most chips I've seen don't extend very far into the edge (1/8" or so) …"

What condition causes the edge to chip in line with the edge in flakes up to near 1/8"?

I have seen this on retail Miyabi knives and wondered what is going on. I've felt it is likely the narrow angle edge, though I don't measure it. I've just resharpened with the existing angle. It is a subject I've not seen mentioned here on the forum notes I've seen.