# What causes different feedback when chopping?



## Silky (Jun 12, 2017)

This is mostly a curiosity question, but what exactly causes different knives to feel different when they hit the cutting board. I understand that the grind and other factors affect the feedback while actually cutting product, but why do knives feel different when they hit something solid? For example, if I was fast chopping an onion or tapping the tip of my knife on my cutting board (a bad habit), some knives seem a little hollow and thud, some feel solid and hard, and some bounce and vibrate. I feel like this feedback affects my preference for knives a bit, but just curious if anyone knows.


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## RDalman (Jun 12, 2017)

Maybe you're talking about the different feelings of soft san mai clad/honyaki(diffhardened)/full hardened mono. Myself I prefer the feeling full hardened mono have on board. But as you say, grind and mass plays a large role as well.


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## fatboylim (Jun 12, 2017)

RDalman said:


> Maybe you're talking about the different feelings of soft san mai clad/honyaki(diffhardened)/full hardened mono. Myself I prefer the feeling full hardened mono have on board. But as you say, grind and mass plays a large role as well.



+1 to all of these (except I am yet to try a honyaki). 

I find heavier mass knives with large core steel and thin lamination have provided the most feedback. You can also get good feedback from medium weight hardened mono steel knives. 

Also worth adding sharpness will differ between metal types, heat treatment and hardness. I find screaming sharp knives will create greater acceleration through foods and will increase the feedback from edge back through the blade and handle.


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## Benuser (Jun 12, 2017)

I guess more than any cladding or alloy, thickness behind the edge is the cause of a damped feeling.


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## osakajoe (Jun 12, 2017)

How sharp the edge is
How thick or thin the blade is
The type of grind on the blade


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## Silky (Jun 12, 2017)

All of this is very interesting. I think it'd be cool if a bunch of people (or maybe someone with a massive collection) tried to separate knives based on different properties and see what exactly cause different types of feedback. I have a few knives that feel very different. My thinned 270mm Heiji feels like a solid slab of steel, really thick and heavy. Very different from a Kono Fuji that I have that has a much thinner grind and feels softer (gentler?) somehow. My most recent purchase, a Denka, seems to have this weird vibration, yet feels very stiff, which was similar to a Mizuno carbon petty I had.


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## malexthekid (Jun 13, 2017)

I think you would get a better idea by blind testing. 

From a materials science point of view clad or mono shouldn't make much of a difference geometry will. 

I tend to think a lot of it is confirmation bias.. it is meant to feel like that so it does. Hence blind testing


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## JaVa (Jun 13, 2017)

Like others have said everything effects feedback. Some of us are more sensitive to it then others. 

IMO there are a four main features that stand out the most

CLADDING vs MONOSTEEL:
Because clad knives have two different metals pressed together that vibrate in two different frequencies and one is sandwiched between two layers, that means when one metal is trying to vibrate the other is keeping it in check and vice versa. So with san mai there's a lot less vibration from the blade to your palm compared to a monosteel. 

TANG TYPE:
Full tang means that you are actually holding in your palm the same metal that the blade is made of. So ass you cut and the metal vibrates (=feedback) you will feel it from your fingers thru your palm to the back of your palm. The more you have of the same metal that the blade is made of pressing in your palm the more feedback it vibrates given it's the same metal. If the tang and/or the handle is a different metal welded to the blade it will again vibrate at a different frequency and less feedback is coming thru. With a hidden tang the softer wood that wraps around the tang will dampen the vibration and mute the feedback. Also the softer the wood, the more muted feedback you will be.

HARDNES: 
With a monosteel blade the harder the steel the more it vibrates and feels more alive. Softer steel will absorb the shocks and vibration more and so should provide less feedback. 

FINISH: 
Different finishes on the blade feels very different. The higher the polish is, the less feel you get. Personally I can't stand sand blasted or similar style finishes because they feel grainy and they feel like they ad friction. Even though it should ad food release properties too, but still it just has a wrong kind of feeling to me. So far a nice kasumi finish seems to work best for me. It feels slick with some feedback too. 

These IMO are the major factors in the equation. 
...but grind, thickness of the blade, thinness behind the edge, weight, handle material, sharpness etc. all bring their own little flavour to the mix.


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## tsuriru (Jun 13, 2017)

malexthekid said:


> From a materials science point of view clad or mono shouldn't make much of a difference geometry will.



lus1:


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## JaVa (Jun 13, 2017)

Yeah, I did forget to mention geometry. I definitely agree with the geometry part of that statement. It certainly makes a big difference in feedback, but I would disagree with the the first part of the statement. 

With two identical knives, with the only difference being one is clad and the other monosteel, the mono steel will always provide noticeably more feedback of the two. The laws of physics state that two different materials pressed against each other (core steel and cladding) will restrict either material from vibrating at their peak resonance frequency as the materials are holding each other down. as the core is trying to vibrate at it's resonance frequency the cladding doesn't vibrate at the same frequency and so is holding the core from vibrating and vice versa. 

Any piece made of single material is free to vibrate at it's resonance frequency without restriction and in this case the monosteel knife can carry that as feedback thru the material in to your hand. 

Make sense?


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## malexthekid (Jun 13, 2017)

No it doesn't... reread my statement. From a materials science point of view there is no difference. Clad or not they are a single piece of steel. Hardening has minimal effect on your spring constants or youngs modulus. And if it did there would be bigger issues with differential displacement etc.

Hence why i said a blind review would be interesting.


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## tsuriru (Jun 13, 2017)

JaVa said:


> Make sense?



Makes a lot of sense. However, it also begs the question: What about a monosteel blade that has been dif. HT with a very soft back and a very hard bevel. Would it still retain it's "toning fork" qualities or would the abrupt change in the fabric of the steel running lengthwise from heel to tip change the behaviour?


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## Benuser (Jun 13, 2017)

Not sure whether the same steel with different hardness -- indentation hardness -- behaves different in that respect.


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## Kippington (Jun 14, 2017)

tsuriru said:


> ...would the abrupt change in the fabric of the steel running lengthwise from heel to tip change the behaviour?



There would not be a noticeable change in its "toning fork" qualities *unless* you hit it hard enough that the metal permanently yields.

In lay-mans terms: You'll end up bending or denting the blade if you hit hard enough to feel/hear the difference in resonance between soft and hard. The soft steel is easier to dent/bend, and of course you can push the harder steel further... but you won't be pushing the limits of soft steel in a well designed knife!


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## LifeByA1000Cuts (Jun 14, 2017)

Sakon AS Nakiri, edge rings like a bell... Takamura R2, feedback as if you were cutting live wires.... both clad kives...


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## tsuriru (Jun 14, 2017)

I have often wondered if knives, any kind of knives, could be analized in terms of resonance, but I lack the training or knowledge to even conceive such a set up, much less make sense of the results. Still, it is intriguing. 

After thought: Perhaps the way to go would actually be to use the knife as a toning fork lined up with helmholtz resonator hooked up to a microphone and into an oscilloscope, but what would this yield? - no idea.


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## JaVa (Jun 14, 2017)

tsuriru said:


> Makes a lot of sense. However, it also begs the question: What about a monosteel blade that has been dif. HT with a very soft back and a very hard bevel. Would it still retain it's "toning fork" qualities or would the abrupt change in the fabric of the steel running lengthwise from heel to tip change the behaviour?



It will have some effect, but probably not enough to be significant. The harder part will carry the resonances easier thru the material, but it's still the same material. The softer and harder parts will have slightly different peak resonance frequencies due to the difference in hardness, but only a little so those resonances still overlaps enough to carry the information forward. So you prob loose some feeling, but not much. Unless the soft part is wildly softer, then it should start to make some difference as their resonance frequencies start move away from each other more.


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## LifeByA1000Cuts (Jun 14, 2017)

@tsuriru much more interesting to get a sweep, or an step response  

Measuring the speed of sound inside the steel (by phase delay) could be interesting too: If there is even a minute influence of temper or alloying content, this would make for easy quality control 

Take an octave of worth of different length blades, in oscillator configurations, and wire up a keyboard...


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## JaVa (Jun 14, 2017)

LifeByA1000Cuts said:


> Sakon AS Nakiri, edge rings like a bell... Takamura R2, feedback as if you were cutting live wires.... both clad kives...



Sure, That's not in anyway impossible. Not all clad knives feel dead. There's a lot of variables that can affect that. Even if two materials are different and so will have different resonance frequencies there can be some overlapping where those frequencies reach each other and those vibrations can be carried thru the blade. 

All materials have their natural peak frequency, which is the point where that material "wants" to vibrate. Let's say that's at 2 kHz. That's where it vibrates the easiest and the most. But it will actually have derivatives (new peaks) at certain intervals to both directions in it's frequency response. The further away from it's natural resonance frequency those peaks appear the less there will be vibrations and the more force is needed to make those derivative vibrations. 

What mostly affects those characteristics are weight, density, hardness and thickness. 

The core steel and the clad steel usually differ in all those characteristics, which should mean a higher dampening effect, but sometimes that equates to two sheets of metal with very similar resonance frequencies. That means some of those peaks just happen to hit the same spots and that means the knife would have a more monosteel like feedback.

That's very easy to test. It's the old "is it a forged knife" test. Flick the blade face with a finger nail. The clearer the sound the more feed back that knife could be able to provide. All my clad knives have a very dead thud except one. That's the Tanaka ginsan migaki. It just happens to have a clad steel and core steel that share some of those overlapping resonance peaks which makes it "ring like a bell" when cutting.

Here's the fun part. That means that probably no two clad knives from the same maker and line will have exactly the same feedback. Since they're hand made that means all those earlier mentioned characteristics will change with every piece. So I'm guessing there's prob someone out there with a Tanaka ginsan migaki gyuto wondering why his knife feels dead and I'm here cheering how great the feedback is on mine.

I haven't tried the finger flick test with my Takamura R2 and it's at work atm so I can't do it until tomorrow, but I'd say it's feedback when cutting is mediocre at best.


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## Kippington (Jun 14, 2017)

The sound of a ringing blade is cool and all, but seriously its a bit silly to see it as a sign of quality.

I mean, if you're gonna test for sound you'd better take the handle off your knife first so it doesn't deaden the vibrations. Then you'd better dangle the blade by a string or something... :razz:
I don't have a Global knife on hand, but I bet their one piece construction plays a nice tune!



LifeByA1000Cuts said:


> Sakon AS Nakiri, edge rings like a bell... Takamura R2, feedback as if you were cutting live wires.... both clad kives...



These two knives? If you were holding them by the handle while you did the test I bet the width of the emoto/neck is the main reason they sounded so different. The one on the Sakon looks very thin in comparison to the Tak.
If you hold them both in a pinch grip and repeat the test, I bet they'll both sound like crap haha! :biggrin:


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## malexthekid (Jun 14, 2017)

JaVa may i ask what is your background? Because unless you have a much higher understanding of materials than i do (which is reasonable but far from extensive, so I'm not being a d!!k i just really want to know more on this and from my reading and engineering materials knowledge this doesn't compute so trying to ascertain the trustworthiness of information) i think you are spreading misinformation.

The properties of steels that relate to natural frequency are going to be almost identical across the types meaning a monosteel or clad have effective the same point natural frequencies and same reaction. As far as I am aware hardness does not affect anything pre-yield point aka they react identically in the elastic range we are working in.

Happy to be wrong here but from the reading i have done there should be no difference in how the blade feels from use. Hence I maintain I would love to see a blind test done to see if this is more psychological than material performance.


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## JaVa (Jun 14, 2017)

My back ground? 
Sure, no probs. 

I used to be a serious hifi enthusiast since I was fifteen years old. That led me to work for a few different home and car audio companies in Finland for ten years From (25 - 35 years old). I've designed home speakers, car speakers and car amplifiers for hifi brands. I've designed and built speaker cabinets and subwoofers. I've been a part of European and World champion competition car sound quality team. I've also competed regionally in car spl competitions. I've designed and built several sound quality competition cars.

During that ten years I've had training by the likes of Focal, Alpine, DLS and Onkyo Which are just some of the companies I worked for or with. All that time I've studied frequency response, vibrations, How to control vibrations and dampen them, how different materials react to vibrations and how those resonances travel thru different materials and how sound waves travel in different circumstances. 

Here is just one example of a case where this principal was used. 
One subwoofer we designed for car audio company we used pressed cellulose as the cone. It was a heavy duty subwoofer that could move a lot of air. The problem is while the cone moves back and forth with great force the cone starts to resonate and develop unwanted distortion in the frequency response. The pressed cellulose is a very tough and irregular material that is VERY "dead" so those unwanted resonances can't appear. The client wanted the speaker to look more high end and demanded a metal cone. 

The metal cone is not the best material since it very easily develops those extra resonances. Our cure for that was pressing two metals together. That made the cone much more stable for the reasons I mentioned in the earlier posts. In our measurements this approach provided almost as good results as the "paper" cone and the client was happy. 

Sure I'm talking about sound pressure and sound waves, but it doesn't matter if the impact to the material that causes those resonances is made by sound pressure or a touch, the same basic laws of physics apply.


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## tsuriru (Jun 14, 2017)

Some very interesting notions here. Some of the science is way over my head certainly the mathematical basis is over my head. Also, Im also trying to look at this from a practical point of view. I think, in a way, some of the discussions here remind me of what musicians sound like when they are discussing instruments. Especially bowed strings like violins or cello or violas. I always found it amazing that violin makers did not make bows - just violins - and that bow makers where a different art altogether. And it was also amazing to listen to musicians discussing their bows as a completely different topic than their instruments. Do violin players judge their bows the same way knife users judge their knives? 

Now bear in mind that these conversations did not include any scientific proof or method - but there was a lot of common experience and intuition and a vague sense of unity regarding certain desirable and undesirable traits. Is there a point? - Of course there is:

Short of compiling a lexicon that defines each and every "type" of feedback from a knife, there is no common language here, and one must fall back on science - or statistics - or both. And even science cannot provide all the answers where individual experience and intuition is concerned, and statistics can be used to manipulate the truth. I think there is too much emphasis on Clad Vs. Mono steel to begin with, and even if this emphasis was really warranted, I think there are not enough realistic parameters or a valid (read minimal) sample to allow for any statistical extrapolation. So we are stuck. And its very hard to go back to the basics since there are still a lot of unknowns here besides the knife:

1) What is the cutting surface?

2) is it wood? If so is it dry or wet? and does that even affect "feedback"?

3) Is one person as sensitive as the next? or do some of us have a higher sensitivity to this so called "feedback"?

4) What are the desirable (and also undesirable) traits one would look for in "feedback"?

5) Can a known state of "feedback" be reproduced over and over again using the same geometry on different materials?


.... And quiet possibly a number of other questions that I didnt even think about.


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## Kippington (Jun 14, 2017)

I'm out of my depth here, but this is way too interesting to pass up. 



JaVa said:


> What mostly affects (resonance) characteristics are weight, density, *hardness* and thickness.



Shouldn't this be stiffness/rigidity instead of hardness?
What I'm trying to be sure of here is the distinction between the properties of a constituent material (e.g hardness), and the properties that also depend on the shape of a structure (stiffness/rigidity).






Here's some references for what I mean:
http://www.audioxpress.com/article/Plastic-Speaker-Cone-History
http://www.nutshellhifi.com/library/speaker-design2.html






This kinda stuff is fascinating to me. I have half a mind to go out and take two pieces of steel with different material properties and grind them to identical dimensions just for testing this out with a drumstick... only I don't want to waste my knife-making steel. Shits expensive yo!

Sorry if this is too off topic.


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## malexthekid (Jun 14, 2017)

Problem is you wont find two pieces of steel with different material properties. In terms of the material properties that effect stiffness for most types of steel, especially those that are used for knives, are basically identical and hardening doesn't effect them, pre-yield.


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## Kippington (Jun 15, 2017)

Thats exactly what I mean. I should be able to differ their hardness and keep their sound the same - hardness being the material property that changes without effecting the resonance (as the elasticity remains constaint).


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## Silky (Jun 15, 2017)

JaVa said:


> Our cure for that was pressing two metals together. That made the cone much more stable for the reasons I mentioned in the earlier posts. In our measurements this approach provided almost as good results as the "paper" cone and the client was happy.
> 
> Sure I'm talking about sound pressure and sound waves, but it doesn't matter if the impact to the material that causes those resonances is made by sound pressure or a touch, the same basic laws of physics apply.



This is really interesting. Were the two different materials made of the same metal or were they different metals like steel and aluminum? I wonder if hardening changes the natural frequencies of the steel any or if maybe the hardness of the material affects anything. Does a higher rockwell hardness relate to a noticeable change in stiffness of the steel or is this more a property of the thickness/construction of the blade? Would a blade that uses nickel liner between the core steel and the cladding in a sanmai blade have any noticeable effect on feeling the way binding two metals together affect the subwoofer? I have a biology background, so material science is quite a bit out of my depth and I don't really know what I'm talking about here.


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## JaVa (Jun 15, 2017)

Oh man, what did I get myself into? :IMOK:

One thing I really want to address first is something that is really surprising to me in all this discussion. The thoughts that hardness/softness would have no effect to the resonance frequency if the metal is the same? That claim really is puzzling to me as hardness is one of the biggest attributes that effect the frequency.

softer = lower frequency response
harder = higher frequency response

also
softer = higher dampening factor 
harder = lower dampening factor 

dampening factor = materials ability to carry those vibration forward (or not to carry forward).

So a softer metal will have lower frequency response and on top of that it's ability carry those vibrations forward are much worse due to it's higher dampening factor. This is the most basic fundamentals of frequency response.


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## JaVa (Jun 15, 2017)

Kippington said:


> I'm out of my depth here, but this is way too interesting to pass up.
> 
> 
> 
> ...



Good catch! :thumbsup:

I completely spaced on stiffness/rigidity earlier and I definitely should have mentioned it as it is another major factor. Although in it's own right, not instead of hardness. And yes, shape too is just as important as it has a direct effect on rigidity.

Very good and informative links you found.


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## malexthekid (Jun 15, 2017)

JaVa said:


> Oh man, what did I get myself into? :IMOK:
> 
> One thing I really want to address first is something that is really surprising to me in all this discussion. The thoughts that hardness/softness would have no effect to the resonance frequency if the metal is the same? That claim really is puzzling to me as hardness is one of the biggest attributes that effect the frequency.
> 
> ...



I think you are confusing terms of and hard and soft)

Yes in general terms you are right but hardness is not a measure of softness/hardness as you discuss it, the better term for that would be malleablity.

Again I will repeat hardness does not affect steels material properties which relate to stiffness.

Stiffness (EI) is determined by two key things firstly geometry (second moment of inertia, I) and secondly a materials properties (such as young's modulus, E).

Natural frequency is basically controlled by mass, stiffness (EI) amd length? As well as some constants like pi to determine what mode of frequency you are looking at.

In your cone example you altered the frequency by essentially adjusting tje length. The two cones still retain the same stiffness but by inserting into each other they are now interacting together and sharing load (as in the cone can't freely oscillate without engaging the other cone therefore altering your frequency of the system).

In a san mai blade the metal is forged into a single piece of steel which will have the same stiffness, and therefore natural frequency as a monosteel blade of identical dimensions. Your weight is basically identical (assuming identical handles).


http://imechanica.org/node/2285


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## JaVa (Jun 15, 2017)

Silky said:


> This is really interesting. Were the two different materials made of the same metal or were they different metals like steel and aluminum? I wonder if hardening changes the natural frequencies of the steel any or if maybe the hardness of the material affects anything. Does a higher rockwell hardness relate to a noticeable change in stiffness of the steel or is this more a property of the thickness/construction of the blade? Would a blade that uses nickel liner between the core steel and the cladding in a sanmai blade have any noticeable effect on feeling the way binding two metals together affect the subwoofer? I have a biology background, so material science is quite a bit out of my depth and I don't really know what I'm talking about here.



We used two different metals, one hard and one very soft. The idea was to have their natural frequency resonance as different as possible and this way raise the constructions dampening factor as high as possible.

As a rule of thump harder materials also tend to be stiffer too.

In a situation where you have two identical knives except one is three layer sanmai and the other differs only by having the nickel liner between the core steel an the cladding. The one with the liner has yet another material with different resonance frequency holding the construction down and adding to it's dampening factor. But the liner is probably so thin the effect would be almost nonexistent.


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## malexthekid (Jun 15, 2017)

JaVa said:


> We used two different metals, one hard and one very soft. The idea was to have their natural frequency resonance as different as possible and this way raise the constructions dampening factor as high as possible.
> 
> As a rule of thump harder materials also tend to be stiffer too.
> 
> In a situation where you have two identical knives except one is three layer sanmai and the other differs only by having the nickel liner between the core steel an the cladding. The one with the liner has yet another material with different resonance frequency holding the construction down and adding to it's dampening factor. But the liner is probably so thin the effect would be almost nonexistent.



Are you saying you used for instance one steel and one copper cone?

And you are correct if a pure nickel liner is used it will have some effect. Though I would suggest its effect is in the realm of negligible given the relative amounts of materials. Sorry didn't read your last sentence.

But the key here is that a monosteel blade and sanmai blade (both made using types of steel) with identical dimensions will have identical resonance response.


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## Ruso (Jun 15, 2017)

Physics aside, am I the only one who does not really notice any difference in response between mono-steel and san-mai?


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## malexthekid (Jun 15, 2017)

Ruso said:


> Physics aside, am I the only one who does not really notice any difference in response between mono-steel and san-mai?



Im with you given the physics actual says there is no difference.


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## malexthekid (Jun 15, 2017)

JaVa said:


> As a rule of thump harder materials also tend to be stiffer too.



When you say this what you are typical actually talking about is Young's modulus. Which is a meaure of stress over strain (or simpler load over deformation).

People perceive materials which deflect more as being softer. Whereas in a material science point of view hardness is a totally different material property. And generally unrelated pre-yield.


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## Nemo (Jun 15, 2017)

Ruso said:


> Physics aside, am I the only one who does not really notice any difference in response between mono-steel and san-mai?



This topic fascinates me.

My monos do feel "louder" on the board (or in food) to me. Having said that, they are in general my most workhorsey/ least lasery grinds, so it could be the grind I guess.

I must have a careful look with my newish Dalman, which is my thinnest mono.


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## JaVa (Jun 15, 2017)

I'll give this one more push and then I'll probably respectfully bow out.

Let's take the "Kippington method". :cool2: 

Let's say we have three identical knives. All without handless. 
1. One is a forged W2 monosteel 58 HRC.
2. One is a forged W2 monosteel 63 HRC.
3. One is a forged W2/SS sanmai 63 HRC. 

You hang them up by a string and hit them one by one with a drumstick with the same amount of force. That will result them to ring/vibrate at their natural resonance frequency. You can hear that ringin by ear but that could be easily measured by an oscilloscope. 

@malexthekid if what you claim is true, that hardness does not affect the natural resonance frequency and/or dampening factor and that the sanmai construction won't affect the natural resonance frequency and/or dampening factor. 

That would mean all those three knives would ring/vibrate at the same resonance frequency and also at the same volume/sound pressure?

I'm pretty sure all those knives would sound completely different with different frequency and different volume. There would be no need for an oscilloscope because the difference in frequency and volume would be clearly audible. 

The 2. knife would have the highest resonance frequency and highest volume. Both 1. and 3. knife would have lower resonance frequency and lower volume, but how they would compare against each other is impossible to predict, although there's a higher chance the 1. knife would be the second loudest with the second highest resonance frequency.

Anyway, that's the way I see it. 
It would be so great try this in real life. I would love to make "the Kippington method" a reality. I'll be happy to be proven wrong to get to learn something new. 

This is a legitimate question, not trying to provoke: how can hardness have no effect on vibrations made by the resonance frequency as a softer material will absorb more of the initial shock of the impact (even make a dent) and also absorb more of the vibrations that follows the impact hence the higher dampening factor? compared to the harder steel that the same force won't make a mark and the full force of the impact is able to translate into vibrations?


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## malexthekid (Jun 15, 2017)

Because a hard material and hardness as a material property are two unrelated things.

Have a read of the link i posted earlier. I'm not having a go just trying to explain some material science, badly I know.

The issue here is the term hardness is misinterpreted as hard material.

All those 3 blades would deflect the same when bent. Would have the same stiffness and natural frequency.

The biggest issue here is that geometry will infact make the biggest difference so in fact the perceived difference may be more related to how the construction methods are best used.


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## malexthekid (Jun 15, 2017)

Also just wanted to add JaVa that all of your theory is sound and i have learnt lots from your experiences, its purely just the fact that hardness does not effect most steel properties (pre-yield).

But it is also very complex san mai is a tad more difficult depending on what it is wrapped in. Aka wrought iron is a totally different beast to carbon steel. So we are all speaking in generalisations because of the multitude of potential options. Mono to honyaki is the best comparison because they are both constructed from a single material.


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## Kippington (Jun 15, 2017)

This is awesome! I'll try this experiment on the weekend and record the results.

I have 1095 and mild steel, I will make two bars of identical dimensions (to the best of my abilities) and quench the 1095 one. Then I will suspend them both and 'ring' them for an answer! :lol2:
I will then drop the same weight on them to break one and bend the other, demonstrating the difference in hardness/toughness between them. Unfortunately I do not have a Rockwell scale.



JaVa said:


> This is a legitimate question, not trying to provoke: how can hardness have no effect on vibrations made by the resonance frequency as a softer material will absorb more of the initial shock of the impact (even make a dent) and also absorb more of the vibrations that follows the impact hence the higher dampening factor? compared to the harder steel that the same force won't make a mark and the full force of the impact is able to translate into vibrations?



If you hit steel hard enough to dent or deform it, there will be a dampening effect yes. The thing is though, we're assuming you don't want your metal to deform in either a knife or a speaker. Hitting it below its denting/bending threshold has no impact on its hardness, as that is exactly what hardness defines: Deformation. The only thing affecting the steel at a low energy impact is its dimensions and elasticity (which remains roughly constaint in steel).
The picture I posted above is a deformed metallic speaker diaphragm, you can see it buckled around the edges. It didn't help the sound quality! 

I do appreciate the civil discussion, even though we don't (yet) agree with each other. If my experiment works, one of us will have to rethink our stance and I wouldn't mind if it was me!


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## JaVa (Jun 16, 2017)

Sounds great! Can't wait! :doublethumbsup: 
This is just way too good to pass up, so on second thought let's keep this train rolling.

Those bars should have a shape that would enhance those resonance properties, meaning they should't be too thick and they should have some length to enhance that difference in their resonance frequency if there is any.

Any chance for another bar with sanmai construction? The main discussion that started this was the difference of the resonance frequency of cladded and non clad knife. 

Although all this has started to make me (slightly) question the significance of hardness regarding the resonance frequency, but not completely sold yet.


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## Kippington (Jun 16, 2017)

I was thinking of that myself.

As you say, a good shape would be thin and long, but the thinner I make them the easier the soft one bends instead of holding its shape (not rigid/stiff). Changing the shape from bar to something stronger like a cone or dome would help stop the steel bending out of shape (which is why bells, speaker cones and the bottom of soda cans are shaped this way!), but that adds a whole other dimension of difficultly to this project which I am not able to attempt. Bar-shaped they will have to stay, and thick enough for the soft one to resist bending. The harder one shouldn't have a problem any of this, of course.

San-mai will have to wait, as forge welding is honestly a PITA to do with my equipment. Hopefully the two bars alone should give us a solid answer.


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## JaVa (Jun 16, 2017)

Kippington said:


> If you hit steel hard enough to dent or deform it, there will be a dampening effect yes. The thing is though, we're assuming you don't want your metal to deform in either a knife or a speaker. Hitting it below its denting/bending threshold has no impact on its hardness, as that is exactly what hardness defines: Deformation. The only thing affecting the steel at a low energy impact is its dimensions and elasticity (which remains roughly constaint in steel).



Yes, the intention is not to hit the steel hard enough make it deform, but my understanding is if the material is soft enough to deform to absorb some of that impact, that those same qualities should enhance it's dampening factor too with a tendency to absorb those vibrations better. 

The thing is that my approach to this is much more practical then scientific. It's been said several times here that those properties in steel should remain constant despite it's hardness. I've read that else where too, but i have a hard time accepting that since my own experiences in practice contradict that.

It is possible that there is some other qualities that I'm not taking into account that are misleading me to make different conclusions. But still not completely sold yet. :scratchhead:


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## JaVa (Jun 16, 2017)

Kippington said:


> I was thinking of that myself.
> 
> As you say, a good shape would be thin and long, but the thinner I make them the easier the soft one bends instead of holding its shape (not rigid/stiff). Changing the shape from bar to something stronger like a cone or dome would help stop the steel bending out of shape (which is why bells, speaker cones and the bottom of soda cans are shaped this way!), but that adds a whole other dimension of difficultly to this project which I am not able to attempt. Bar-shaped they will have to stay, and thick enough for the soft one to resist bending. The harder one shouldn't have a problem any of this, of course.
> 
> San-mai will have to wait, as forge welding is honestly a PITA to do with my equipment. Hopefully the two bars alone should give us a solid answer.



Sounds about right.


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## JaVa (Jun 16, 2017)

Meanwhile...
Riddle me this, riddle that...

In my understanding forging too affects the natural resonance frequency of the steel. This time I'm not talking about hardness. If you have two identical mono-steel knives made of same steel and they have the same hardness, but one is forged and one is not. What changes in the steel to make that difference in their natural resonance frequency. 

Again, if you flick those two knives with your finger nail, the forged knife will ring and the other will have a damped thud. This is something I have tried several times and the result is always the same. All mono-steel knives I've done this to ring at least to some extent and all the non forged ones don't.

What is the change to result this?


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## tsuriru (Jun 16, 2017)

JaVa said:


> This is something I have tried several times and the result is always the same. All mono-steel knives I've done this to ring at least to some extent and all the non forged ones don't.
> 
> What is the change to result this?



Could the answer to this be in the realm of crystallography? Could it be that a blade made in a stock removal technique then heat treated "grows" a more uniform crystalline lattice where a forged blade of the same material is being subjected to both crystalline growth and the reversal of such growth (in some of the crystal types) and also a physical mutation of the lattice due to the the impact caused by the hammer blows? That would cause a change in sound no?


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## JaVa (Jun 16, 2017)

Sounds plausible to me. The more uniform structure of a material makes it easier for the vibrations to travel.


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## malexthekid (Jun 16, 2017)

JaVa said:


> Yes, the intention is not to hit the steel hard enough make it deform, but my understanding is if the material is soft enough to deform to absorb some of that impact, that those same qualities should enhance it's dampening factor too with a tendency to absorb those vibrations better.
> 
> The thing is that my approach to this is much more practical then scientific. It's been said several times here that those properties in steel should remain constant despite it's hardness. I've read that else where too, but i have a hard time accepting that since my own experiences in practice contradict that.
> 
> It is possible that there is some other qualities that I'm not taking into account that are misleading me to make different conclusions. But still not completely sold yet. :scratchhead:



Can I ask where your experience comes from? is it comparing hard materials with soft materials (aka paper cones with metal cones)? Or is it comparing the same metal with different hardnesses?


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## malexthekid (Jun 16, 2017)

JaVa said:


> Meanwhile...
> Riddle me this, riddle that...
> 
> In my understanding forging too affects the natural resonance frequency of the steel. This time I'm not talking about hardness. If you have two identical mono-steel knives made of same steel and they have the same hardness, but one is forged and one is not. What changes in the steel to make that difference in their natural resonance frequency.
> ...



What makes you think there will be a change in natural frequency (resonance) where have you seen such identical knives to make this assertion.


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## LifeByA1000Cuts (Jun 16, 2017)

While youngs modulus and spring thingamajig constants might be effectively the same about steels of varying alloys and tempers - is there a concept of "lossiness" (percentage of vibrations in the material being turned into heat rather than propagated) in mechanics too, and might it be very well dependent on these properties?


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## malexthekid (Jun 16, 2017)

LifeByA1000Cuts said:


> While youngs modulus and spring thingamajig constants might be effectively the same about steels of varying alloys and tempers - is there a concept of "lossiness" (percentage of vibrations in the material being turned into heat rather than propagated) in mechanics too, and might it be very well dependent on these properties?



The only reference I can find (admittedly just a quick google search) in regards to this concept of lossiness relates to magnetics... and it mentions soft metallic magnets. Again, not forms of steel. Remember steel essentially refers to carbon steels of varying degrees (note there is some minor variation between stainless steel and carbon steel, but it is only a few percent typically, not enough to make a real difference I would imagine).


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## JaVa (Jun 16, 2017)

I'll be enjoying some very scrumptious humble pie. :spin chair: 

I just went thru all my 14 knives flicking them to prove my point. I did the same already earlier with 6 of my knives which I had at home. The first time with those 6 knives my findings were the same, as I've encountered earlier when doing this. My forged Mac (my only forged Mono-steel) ringed clearly with the highest note and the loudest. All sanmai knives produced a silent thud. 

Now I have all my knives from work too and lo and behold I stand corrected. My Shiro Kamo B2 iron clad knife which is hardened to 64HRC really rings like a bell. By far with the loudest volume. It's crazy how much it vibrates and the Mac can't compete at all. There is still those 5 clad knives that are completely dead of vibrations which I just happened to have at home earlier. And then there's the seven forged clad knives that vary in their "ringiness"(ability vibrate and carry information).

What really makes my head spin is that I can't find any common nominators on which to base why others are vibrating and others aren't. I have Nakiris, gyutos, a sujihiki and pettys. I have wide bevels, convex grinds, thin, thicker, western, wa, etc. nothing seems to be constant nominator in why the behavior is happening. Petties don't vibrate much due to their shortness, but outside of that, I can't find any conclusion. 

For example Wakui Kasumi and Itinomonn Kasumi stain-less are very similar 240 gyutos. Weight, size, grind, profile etc share a lot. There's differences, but not big enough to result in the huge difference they have in their behavior. 

Wakui is very lively with a clear, one of the loudest tones and you can feel the blade vibrate pinching the neck. 

Itinomonn is completaly different with a very silent responce and almost completely void of vibrations pinching the neck. 

Kohetsu HAP40 is thinned and reprofiled. slightly smaller, way thinner, has a different profile etc, but sounds and behaves about the same as the Itinomonn. 

My mistake was probably that I confused hardness with hard material like malexthekid suggested. I have a hard time accepting that if hardness changes all other atributes would stay the same. Still on the fence though. :razz: 

But put all that aside, one thing doesn't change. No matter what results this (grind, material, finish, profile, thickness etc) but if a blade has the tendency to vibrate (ring) that means it has the ability to carry the information from the cutting board thru the blade. If a knife does not vibrate, it can't carry that information, because the high dampening factor means there is no information moving in the blades structure and those vibrations are absorbed before it ever reaches your hand. And no other attribute can bring that information back. no?


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## tsuriru (Jun 16, 2017)

JaVa said:


> no?



Is this with or without handles? and if it is without handles how is the blade fixed when you "twang" it?


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## fatboylim (Jun 16, 2017)

Awesome pop corn material guys. All excellent view points and exchanges of approaches. More please.


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## JaVa (Jun 16, 2017)

tsuriru said:


> Is this with or without handles? and if it is without handles how is the blade fixed when you "twang" it?



I'll probably get flamed for this, but in this case I'd say it doesn't really matter if it has a handle or not. If for some reason the handle is restricting the blade (which it might) to resonate it means in that set up the blade is unable to provide information. So regardless of the reason why, if the blade is able to vibrate, that should mean information is provided. 

But I have yet to flick a forged gyuto with any handle on them that would not "ring". at least some what. but I have flicked several non forged knives and again regardless of handle the sound has always been more muted.

Pinch grip the neck with your index finger and thump. Don't squeeze. Let the blade hang loose the tip pointing the floor and the edge pointing away from you. With your other index finger flick lightly to the middle of the spine. What do you hear and what do you feel in your fingers?


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## JaVa (Jun 16, 2017)

Squeeze the neck enough that you dont't drop the blade and that the blade won't swing. Better to be safe. :lol2:


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## tsuriru (Jun 16, 2017)

JaVa said:


> So regardless of the reason why, if the blade is able to vibrate, that should mean information is provided.



Actually this makes sense. Sort of similar to a natural "harmonic" on a string right?


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## malexthekid (Jun 16, 2017)

The presence of the handle would still have some effect, given that your grip isn't strong enough to stop the oscillation passing it.

And I would suggest the difference between the types of blade is probably to do with geometry. Handle material, style etc.


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## JaVa (Jun 17, 2017)

tsuriru said:


> Actually this makes sense. Sort of similar to a natural "harmonic" on a string right?



Exactly.


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## JaVa (Jun 17, 2017)

malexthekid said:


> The presence of the handle would still have some effect, given that your grip isn't strong enough to stop the oscillation passing it.
> 
> And I would suggest the difference between the types of blade is probably to do with geometry. Handle material, style etc.



Yes, the handle will definitely have an effect on the result. The reason I said it did not matter is that if you do the vibration test without a handle and the blade vibrates (carries information). That knowledge has very little use in real world. Because if you put the handle on it and it won't vibrate any more, the information does not help very much. Plus most people buy knives with handles anyway. 

So if you wan't to know how lively a certain knife feels, do the test as is, meaning with the handle. Also if the blade clearly vibrates, but it feels dead when cutting, the handle is probably the biggest issue (and/or grind). 

If you pinch grip while cutting and you have a knife that clearly "rings" with the "flicking test" that information will at least reach your thump and index finger anyway (regardless of the handles effect), just might not reach all the way to your palm. 

BTW The liveliness of a blade is not that big of a deal for me personally. It's just something that is what it is, just one feature with all the other features. I just happen to be a little sensitive in the matter. My favourite knife is lively, but my second is not that much and I have much livelier knives in my lineup that still don't get much use.


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## Kippington (Jun 18, 2017)

JaVa said:


> ...I'd say it doesn't really matter if it has a handle or not...
> 
> ...I have yet to flick a forged gyuto with any handle on them that would not "ring". at least some what. but I have flicked several non forged knives and again regardless of handle the sound has always been more muted.



I have to disagree. I think the handle has a huge effect.
I recorded this as a video response. This knife was forged and heat treated by me, 1084 monosteel.

[video=youtube;8CcQLDNh7bQ]https://www.youtube.com/watch?v=8CcQLDNh7bQ[/video]

I'm working on my other 'Kippington experiment' now. Gonna use W2 and mild for this one, hopefully I get the quench done before it gets too dark out.


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## JaVa (Jun 18, 2017)

Wow, that's super cool! Never thought the handle would have such a dramatic effect. 

I have tested over 10 forged mono-steel knives and even several more of non forged mono-steel knives, all with different kind of handless and all the forged ones have had a much clearer sound. 

Although just to be clear, I never meant that the handle would have no effect on "ringing" properties of a knife, because of course it would have. What I meant was that If a knife would have a tendency to vibrate and ring, then regardless of the handle that it still would at least to some extent. Even if the handle would mute the effect I never thought that a handle could kill the vibrations completely. Now I know better. :doublethumbsup: 
I'm actually very excited. Cool stuff! 

Love to be proven wrong and learn from that. Even more so, alway absolutely loving it to see something proven in practice. We can talk about stuff until we're blue in the face, but until it's shown in practice, its just theories and talk. 

Can't wait for the "Kippington experiment"! :cool2:

Still, if that's the handle used on that knife, when in use, it will have very limited to non existing feedback due to the the dampening factor created by the handle. And still... Vibration is information, that is the only way information can travel from the cutting board to your hand. So regardless of what causes the blade to be able to vibrate or what kills those vibrations. Vibrations is the only thing that can enable feedback. 

BTW Any chance you could add one more billet that could be non heat treated to see if there is any difference?


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## Kippington (Jun 18, 2017)

JaVa said:


> Although just to be clear, I never meant that the handle would have no effect on "ringing" properties of a knife...



Yea apologies for that, I did quote you a bit out of context to get a point across. :O

This experiment is proving to be more difficult then I had imagined. This is where I'm up to.
I took my W2 and structural mild steel bars (both annealed from the mill):






They have different dimensions so I marked them and cut them like so:





Then clamped them together and went to grinding:





The mild steel was thicker then the W2 so I ground the surface to get them to a similar thickness. And this is what they look like now, no heat-treatment having been done:






Close enough, right?

The problem is... they already sound different! When struck, they share the same pitch but the mild steel continues ringing for something like 2 seconds while the W2 dies off almost immediately! I'm at a loss to explain why this is...
There is mill scale on the surface of the mild steel that might be affecting the vibrations. It's too late for me to do any more grinding so I will have to wait until tomorrow!


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## JaVa (Jun 18, 2017)

Looking good!  

Do those two steels share the same structural properties or Is there a difference in hardness, weight, density etc. That could affect that. Look, to me it's a no brainer that two different steels cut to a same size and shape would sound different of the bat. Even if their properties would be very close, that's not the same as identical. Not saying that's the reason here since it's been so strongly suggested otherwise. Just throwing it out there. 

Even if the note is the same or close, the other steel might have a much higher dampening factor and it absorbs the vibrations quicker hence rings a shorter amount of time. 

I'm very interested if someone would now their hardness? Which is harder and does the harder or softer steel ring longer? 

There is also another possibility I'm considering, but I would love to hear first the answers to these questions before going there.


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## JaVa (Jun 18, 2017)

Can you weigh those pieces?


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## BloodrootVW (Jun 18, 2017)

So I am a little late here to the game here but a very interesting discussion. I wonder if, in addition to the internal properties of the steel, the cross-sectional geometry and distal taper have much more to do with how a knife vibrates. The edge would vibrate like the string on a violin much as the geometry allows. Also the spine would vibrate at a different frequency than the edge probably due to their relative thicknesses.That said, I also recognize that tone woods (Rosewood, etc) operate differently that woods of similar hardness that are not in that group (Oak, Hickory).

I look forward to hearing more about what you all find out.


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## malexthekid (Jun 18, 2017)

This is where having one of the material science experts weigh in would be great. 

Also cross sectional geometry really is important and it is not just a linear proportion but something like a x^4. So minor variation could have reasonable effect.


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## JaVa (Jun 18, 2017)

BloodrootVW said:


> So I am a little late here to the game here but a very interesting discussion. I wonder if, in addition to the internal properties of the steel, the cross-sectional geometry and distal taper have much more to do with how a knife vibrates. The edge would vibrate like the string on a violin much as the geometry allows. Also the spine would vibrate at a different frequency than the edge probably due to their relative thicknesses.That said, I also recognize that tone woods (Rosewood, etc) operate differently that woods of similar hardness that are not in that group (Oak, Hickory).
> 
> I look forward to hearing more about what you all find out.



To my knowledge the cross sectional geometry and distal taper of the blade has a lot to do with the resonance frequency and yes, the edge and spine would vibrate at different frequencies with each other. But that opens a new can of worms. As a general rule the thinner the blade is the less there's difference in the frequencies between different parts of the blade and the blade should ring better.

But there are other principals in play. Unfortunately I gotta run. I'll get back on this when I have a chance.


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## JaVa (Jun 18, 2017)

So we need to reel back a bit. Like somewhere earlier I mentioned that all things have a natural resonance frequency and that it's affected by certain properties like weight, shape size, density, material etc etc. and that usually things have several resonance frequency points, but only one is the natural point (where the object will vibrate the most). All those frequency points have a certain wave length which can vary anything from narrow to wide.

As the edge and spine are vibrating at their natural resonance frequency which is going to be different from eac other, if some of those resonance frequencies peak at the same places it enables the object to hold those vibrations better. That can be further assisted by if the wave length is wide as that helps the frequencies to be at the same spots for longer. 

you can have a heavy workhorse knife that when tested will clearly vibrate, but might feel lifeless compared to a thinner blade that vibrates a little less. This is caused by the fact that the heavier that the heavier knife needs more force to cause those vibrations. A thinner knife will vibrate with less force and on the cutting board whan used right there isn't that much force directed to the edge anyway. 

As the edge is the thinnest part of the blade there's also the matter, that some of the power of the vibrations is not only lost due to the dampening factor, but because the thinnest part of the equation receives the initial hit and transfers those vibrations thru to the increasing mass and tries to make the heavier part to vibrate. 

So the more of the cross geometry, shape, distal taper and other properties are in tune with those resonance peaks as possible, (and the wider those peaks are the better) that would make it a lot easier for those vibrations to carry through.


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## Don Nguyen (Jun 18, 2017)

You could study a bit into this through modal frequency analysis, at least for simplified models (monosteel).

Every knife is going to have different frequency characteristics if their geometry is even a little bit different. To do a consistent test you could have the same exact profile and same exact grind - not that difficult if you know what you're doing. Easier still would be to make little tiles of steel, like the keys on a xylophone. Use the same core steel, have some monosteel, some cladded, unhardened, hardened, tempered, untempered, forged, cold forged, etc.

Handles will certainly alter the characteristics. If you study into classical sword designs, practically everything is tied into vibration. The ratios can be derived to be quite similar to musical instruments. Dimensional ratios were scarily similar to fret patterns on a guitar. What happens if you mute certain parts of a guitar string? You could dampen the sound, or you may hit a harmonic node. Same thing with steel - it's all about vibration nodes throughout the shapes.


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## Kippington (Jun 19, 2017)

Don Nguyen said:


> Easier still would be to make little tiles of steel, like the keys on a xylophone. Use the same core steel, have some monosteel, some cladded, unhardened, hardened, tempered, untempered, forged, cold forged, etc.



Yes this is similar to what I'm trying to do. These results are not what I expected so I might have to retract some of my earlier statements. 
I double checked the tile dimensions by holding them side by side (you can't see the gap between them):






And checked the thickness with a back-light and a straight edge. Not perfect but close enough:






Unfortunately I can't weigh them, don't own a set of scales.
So here I recorded the audio. Each piece was thrown up in the air and struck. I can hear a distinct difference between them... they share the same pitch but the W2 refuses to carry the vibrations for as long as the mild steel.

[video=youtube;W_XaaP3rT9c]https://www.youtube.com/watch?v=W_XaaP3rT9c[/video]

Blegh, I need to re-think what I said earlier.
I'll go and quench the W2 in water now. I'm guessing it'll grow slightly larger then its brother as this is what martensite is _supposed_ to do over pearlite. But heck, I'm not so sure of myself anymore.


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## Kippington (Jun 19, 2017)

Ok, I've quenched it in water:

[video=youtube;XScJEd88-wU]https://www.youtube.com/watch?v=XScJEd88-wU[/video]

After the quench, the W2 has grown slightly larger in all directions as it should have - thank goodness! :lol2:






Here's what it sounds like after the quench - the same as before if you ask me.

[video=youtube;lGg5_56R2SM]https://www.youtube.com/watch?v=lGg5_56R2SM[/video]

I think if I was to differentially harden it there would be no significant change to the resonance in the steel.

I'm not sure what else to pull from this...
Should I differentially harden the W2 or break it instead while its still hard? Or maybe I could hit both the tiles with the same force to break one and bend the other if that helps prove anything, kinda like a home-made Charpy impact test. I haven't tempered the W2 so it _should_ be right up there in hardness with very poor toughness.

Can anyone explain to me why the mild steel reverberates for so much longer then the W2?


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## RDalman (Jun 19, 2017)

I can just contribute my "feeling" on this subject... But I'm fairly sure I feel a considerable difference on blades with same (my own) grind. I've tried this with many knives, differentialy hardened, soft clad san mai and full hardened mono. 

A full hardened feels more "direct" and shorter resonance on board, like it doesn't want to play music... While knives with soft steel will have a little bit more vibrations to them. I mainly use face grain wood boards also may be worth noting.


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## LifeByA1000Cuts (Jun 19, 2017)

What I meant with "lossy" is friction inside the material when it is subjected to vibration, which will obviously take energy away and reduce "sustain"...


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## merlijny2k (Jun 19, 2017)

Reading this discussion I started out being pretty sure the hardness didn't matter much given Young's modulus stays constant and so on but it seems I was wrong.


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## merlijny2k (Jun 19, 2017)

One suggestion: for the sake of getting the best possible experiment it seems better to do the hitting with a piece of soft material rather than another piece of steel to rule out local plastic deformation.


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## merlijny2k (Jun 19, 2017)

The dissipation of vibrational energy to heat is typically called hysteresis and come to think of it it is not too far fetched that a different crystal structure has different hysteresis value.


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## merlijny2k (Jun 19, 2017)

Hysteresis is of a bit more obvious interest in springsteel rather then knifesteel so there is some scientific literature on this and turns out that yes: there are measurable and significant differences in hysteresis depending on both crystal structure and hardness of the steel. See for example here:
https://www.researchgate.net/public...sducers_using_AISI_4340_steel_spring_material


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## LifeByA1000Cuts (Jun 19, 2017)

I always thought hysteresis was what kept thermostats from becoming buzzers  Or what was up with the melting point of Agar... So are we talking a fully reversible effect, or energy going into fatigueing the material by slowly knocking atoms out of whack?


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## Kippington (Jun 19, 2017)

Interesting stuff merlijn, thanks for the link.

I'm thinking the grains might play a larger factor in my test than the hardness. It definitely shows up in that hysteresis paper (check out Fig 11. the difference in error between coarse martensite vs martensite, both @ 45 HRC).

It also just occurred to me that when I cut the bar stock, I cut the W2 against the grain while cutting the mild steel along it (if they were cold rolled). 






I will modify the grain in the mild steel and see if that changes anything.



merlijny2k said:


> ...do the hitting with a piece of soft material...


Yes I made sure to do this. I used one of those soft bamboo chopsticks so there was no chance of denting the steel.


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## Kippington (Jun 19, 2017)

Bleh, normalizing and grain refinement had no effect on the mild steel acoustics.
Heat treating does not seem to have a large effect on vibrations in steel, which makes sense in terms of elasticity... but I'm still at a loss to explain why the two steels sound so different. It really seems to back up what some people are saying about the feel between clad vs mono-steel, much to my surprise.


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## malexthekid (Jun 19, 2017)

Kippington said:


> Bleh, normalizing and grain refinement had no effect on the mild steel acoustics.
> Heat treating does not seem to have a large effect on vibrations in steel, which makes sense in terms of elasticity... but I'm still at a loss to explain why the two steels sound so different. It really seems to back up what some people are saying about the feel between clad vs mono-steel, much to my surprise.



What is the chemical composition of W2?

Still doesn't explain the perceived difference for Honyaki


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## Kippington (Jun 19, 2017)

This specific *W2*:
Certification: *C*- .916 *Si*- .296 *Mn*- .215 *P*- .0050 *S*- .0020 *Cr*- .069 *Ni*- .042 *Mo*- .008 *V*- .165 *W*- .005 *Cu*- .047 *Sn*- .0060 *Al*- .006
Annealed Structure: 98% spherodized carbides



malexthekid said:


> Still doesn't explain the perceived difference for Honyaki


Agreed!


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## merlijny2k (Jun 19, 2017)

Apparently there is even a difference in sound velocity between stainless and non stainless:
http://www.classltd.com/sound_velocity_table.html


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## merlijny2k (Jun 20, 2017)

Cast Iron is way off in terms of shear wave velocity, bet that gives a very different sound. Also, differences in shear wave velocity affect the harmonic itself while difference in hysteresis only duration (damping).


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## merlijny2k (Jun 20, 2017)

http://www.elcometer.com/en/velocity-chart-of-preset-materials.html


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## merlijny2k (Jun 20, 2017)

Hete is the most detailed page I could find, geared towards builders of musical interest where tonal properties of materials are of obvious direct interest.

https://sites.google.com/a/techrent...tes/PAN-PT878/Pipe-Material-Sound-Speed-Table


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## merlijny2k (Jun 20, 2017)

Looking at it from this angle, there should be a far larger tone difference between brass and steel than between steels. Happen to have any leftover brass?


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## merlijny2k (Jun 20, 2017)

Also have you tried Soundbeam or another oscilloscope app? I'm curious to see the actual waves. Seeing where they differ might give us some usefull info like is it mostly the frequency or damping behaviour etc.


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## merlijny2k (Jun 20, 2017)

Deleted, accidentally posted double.


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## JaVa (Jun 20, 2017)

Hats of for doing the test Kippington. It's been a lot of fun to follow the progress! :cool2: 

Still My heads spinning. In the alternate universe that I live, it's puzzling to me how two pieces that not only have a difference in hardness, but also differ in dimensions and still share the same tonal characteristics. That's astounding and super cool at the same time.

I'd be brave enough to suggest that in the light of the results, would it be fair to assume, that if the you make a mono steel W2 knife and a knife with the W2 core steel clad with the mild steel tested here, that the mono steel knife would vibrate more of the two and provide more feedback? 

Or am I too quick to draw?


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## Nemo (Jun 20, 2017)

JaVa said:


> Hats of for doing the test Kippington. It's been a lot of fun to follow the progress! :cool2:
> 
> Still My heads spinning. In the alternate universe that I live, it's puzzling to me how two pieces that not only have a difference in hardness, but also differ in dimensions and still share the same tonal characteristics. That's astounding and super cool at the same time.
> 
> ...



This is probably a reasonable hypothesis but in complex systems like this I think you actually have to run the experiment to be sure. There are potentially a lot of variables affecting the outcome, and we don't really know which is important. Finding out which is important by experimentation is of course the basis of scientific thinking.

And thanks Kippington for running the experiments. It's been fascinating.


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## malexthekid (Jun 20, 2017)

The problem with third test is that there is no control. There may be an external factor affecting results and without a control to use as a baseline that may be skewing results.

Still interesting.


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## Kippington (Jun 20, 2017)

Yeah thanks guys, it was a fun test to do!

I'm honestly still surprised by the results. From the beginning I could pick up one of the tiles with my eyes closed, ring it, and _I always knew which piece of steel I was holding_ despite the fact they were indistinguishable to me in shape, weight and texture. This always remained constant throughout heat-treating.



JaVa said:


> ...the mono steel knife would vibrate more (than the clad knife) and provide more feedback?



I initially thought incorporating the mild steel (which vibrates more) into a knife would cause it to vibrate more. But you're talking about them damping each other out, yeah? That does make sense to me.



malexthekid said:


> The problem with third test is that there is no control. There may be an external factor affecting results and without a control to use as a baseline that may be skewing results.



How would I utilize a control in this test? Come to think of it, I didn't see a control in the paper posted earlier in the thread (I might be wrong).



JaVa said:


> ...it's puzzling to me how two pieces that not only have a difference in hardness, but also differ in dimensions and still share the same tonal characteristics.


I'm guessing the dimension change was so slight that if it did have an effect on tone it was too small to tell. That might be another experiment for another time!

The interesting thing about hardness is that it measures something _beyond_ elasticity. I mean, the machine that does the test itself has to make sure to bypass any elasticity before it even begins its measurement. On the wiki for the Rockwell scale:



*Operation*
​_The determination of the Rockwell hardness of a material involves the application of a minor load followed by a major load. The minor load establishes the zero position. The major load is applied, then removed while still maintaining the minor load._







So basically the vibrations happen within the confines of the minor load, before the machine has even established a zero position (bypassing elasticity/Young's modulus) for measurement of the major load (hardness).


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## malexthekid (Jun 20, 2017)

How to utilise a control is for this experiment out of my skill set.

For something like this you need to produce a sample which you can predict the result to make sure it is all working perfectly. Not saying it isn't just you can never discount it unless you have proved it.


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