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Is sharpness directly related to thickness

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welshstar

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Hi

Quick question

I have seen in the knives that ive purchased over the last 6 months that the thinner the knife the sharper it comes OOTB. Is this just the way it is and to get razor sharpness you need laser blades ? or can thicker knives acheive the same sharpness ?

Alan
 

Darkhoek

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I have a Deba that is 9mm over the shoulders. It is one of my very sharpest blades. Steel, grind and honing has everything to do with it. A laser blade will wedge less and perform better on cutting harder stuff, but for raw meat and fish a Deba will probably work just as good as a laser. There is no direct connection between sharpness and thinness of a blade. There are a lot of factors in play.

DarKHOeK
 

Pensacola Tiger

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No, there is no correlation between sharpness and thinness. A crappy edge on a very thin knife will be perceived as sharp, and that's what your noticing on your OOTB edges.


Hi

Quick question

I have seen in the knives that ive purchased over the last 6 months that the thinner the knife the sharper it comes OOTB. Is this just the way it is and to get razor sharpness you need laser blades ? or can thicker knives acheive the same sharpness ?

Alan
 

Larrin

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Thickness doesn't control sharpness, it controls cutting ability.
 

Citizen Snips

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sharpness is sharpness.

thickness affects performance in certain tasks
 

Eamon Burke

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Literally speaking, yes. It is exactly correlated.

Because "sharpness", as defined, is the ability to cut with ease. Thinness behind the edge improves cutting efficiency, by way of directing stress/pressure over a smaller overall object. This is why Straight Razors are so thin--because it allows them to have the bulk of the pressure applied over a smaller, more directed area, meaning you need less pressure to cut hair(which is good when pressure is being applied to your face).

As far as knife performance, thinness is just one way of producing a knife that gets through food well. Essentially, by making a knife very thin, you can do one of two thing:
1. Drop weight, and create a knife that is either balanced where you like it or simply lightweight overall, which reduces fatigue over long shifts.
2. Skimp out on perfecting the distal taper and face bevels, because you are relying on thinness to provide efficiency. This is why Tojiro DP series is very thin--1.5mm spine thickness at the heel--thin stock, decent profile, slackbelt it, cut & ship.

Generally, thinner means:
Cuts better when dull
More likely to snap when stressed sideways(not an issue in a kitchen, except the tips)
lighter weight blade(can be good on long knives that are too front-heavy, but can make things very handle-heavy...weight on top of the edge helps cut)
adds flex
less steel to work with(faster sharpening, faster overgrinding, faster overheating)
Less likely to wedge
More likely to stick
cheaper material stock if grinding the blade
 

jaybett

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A keen edge can be put on just about anything that can be ground. Years ago, I saw a demo, put on by the Forest Service, on fighting wild fires. What surprised me was all their tools, were sharpened, including the picks and shovels. The edge on the shovels, was able to cut hair and thread.

Double bevel edges are similar to the triangular shape of an axe. If a knife is sharpened but not thinned behind the edge, the edge will get thicker and thicker. Dave notes a saying in his video, "The more I sharpen my knife the duller it gets".

One thing has puzzled me, is that in theory thin knives should be the most efficient cutters. While they are good at making fine cuts, the thicker so called work horse or all around knives are easier to cut items such as tomatoes and proteins. I've found it easier to cut up a bag of chicken breasts for sates, with a Sugimoto 22, a heavy cleaver, then with a Masmoto KS 270mm sujihiki. I believe other forum members have experienced something similar when they have tried a thicker gyuto such as a Shigefusa or a Wattanabe.

What the medium thick knives have in common are wide bevels. My hunch is that once the knife has gone a quarter inch in, that the thicker part of the knife starts to force the veg/protein apart. The weight of the knife also plays a part.

At this stage of my experience with Japanese knives, I am finding that I prefer thin knives for precision work, while thicker knives for prepping larger amounts of food.

Jay
 

Eamon Burke

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One thing has puzzled me, is that in theory thin knives should be the most efficient cutters. While they are good at making fine cuts, the thicker so called work horse or all around knives are easier to cut items such as tomatoes and proteins. I've found it easier to cut up a bag of chicken breasts for sates, with a Sugimoto 22, a heavy cleaver, then with a Masmoto KS 270mm sujihiki. I believe other forum members have experienced something similar when they have tried a thicker gyuto such as a Shigefusa or a Wattanabe.
I think it's the sticking that makes the thin ones feel less efficient. That and the lack of weight behind the edge. But mostly it's the sticking. Ever used a thick knife with a crappy flat grind? It's actually worse than thin with a crappy flat grind.
 

Citizen Snips

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Literally speaking, yes. It is exactly correlated.

Because "sharpness", as defined, is the ability to cut with ease. Thinness behind the edge improves cutting efficiency, by way of directing stress/pressure over a smaller overall object. This is why Straight Razors are so thin--because it allows them to have the bulk of the pressure applied over a smaller, more directed area, meaning you need less pressure to cut hair(which is good when pressure is being applied to your face).

As far as knife performance, thinness is just one way of producing a knife that gets through food well. Essentially, by making a knife very thin, you can do one of two thing:
1. Drop weight, and create a knife that is either balanced where you like it or simply lightweight overall, which reduces fatigue over long shifts.
2. Skimp out on perfecting the distal taper and face bevels, because you are relying on thinness to provide efficiency. This is why Tojiro DP series is very thin--1.5mm spine thickness at the heel--thin stock, decent profile, slackbelt it, cut & ship.

Generally, thinner means:
Cuts better when dull
More likely to snap when stressed sideways(not an issue in a kitchen, except the tips)
lighter weight blade(can be good on long knives that are too front-heavy, but can make things very handle-heavy...weight on top of the edge helps cut)
adds flex
less steel to work with(faster sharpening, faster overgrinding, faster overheating)
Less likely to wedge
More likely to stick
cheaper material stock if grinding the blade
kinda disagree. this would mean that a straight blade with a dull edge is sharper than a CCK with a very refined and stropped edge.

sharpness, performance and efficiency are all different in my opinion.

i think your definition of sharpness applies in most places but here on these forums, i would have to disagree
 

Eamon Burke

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kinda disagree. this would mean that a straight blade with a dull edge is sharper than a CCK with a very refined and stropped edge.

sharpness, performance and efficiency are all different in my opinion.

i think your definition of sharpness applies in most places but here on these forums, i would have to disagree
It would seem that you are saying that a cck is not thin. Mine's pretty bloody thin, and huge to boot. It is kind of a prime example of what I am talking about--lots of metal behind a VERY small area, and it does cut, even when dull, pretty dang well. My CCK is a great performing knife, just because it is thin--the steel sucks, and the profile is ok, but the design of it is pretty fantastic.

It's not my definition of sharpness--"sharp" just means "cuts well". To use it colloquially to mean something more specific will only cause confusion, and is unnecessary, since there are more accurate terms for the qualities of a knife that are often refered to as "sharpness". One that comes to mind is "a polished edge". A tissue-paper slice test does not test the cutting efficiency of a tool--only shows how well the bevels are matched and polished--and I've seen more than one knife that will push-cut paper and still cuts food like crap.

An example of a knife that is thick and cuts well would be a Shigefusa--thick, and cuts with primo efficiency, because Iizuka san has nailed the profile, distal taper, balance point and face grind. A thick knife that cuts like crap would be a Farberware--thick in the back, poorly ground, and not matter how you sharpen it, it will always cut like crap. Compare that Farberware to a Tojiro DP, which has a simple grind and bad balance, and the Tojiro will out perform the Farberware even when dull--simply because it is thinner.

There are factors to a knife other than cutting power, but when it comes to that, the CCK 1303 is a bang-for-the-buck MONSTER.
 

Citizen Snips

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It would seem that you are saying that a cck is not thin. Mine's pretty bloody thin, and huge to boot. It is kind of a prime example of what I am talking about--lots of metal behind a VERY small area, and it does cut, even when dull, pretty dang well. My CCK is a great performing knife, just because it is thin--the steel sucks, and the profile is ok, but the design of it is pretty fantastic.

It's not my definition of sharpness--"sharp" just means "cuts well". To use it colloquially to mean something more specific will only cause confusion, and is unnecessary, since there are more accurate terms for the qualities of a knife that are often refered to as "sharpness". One that comes to mind is "a polished edge". A tissue-paper slice test does not test the cutting efficiency of a tool--only shows how well the bevels are matched and polished--and I've seen more than one knife that will push-cut paper and still cuts food like crap.

An example of a knife that is thick and cuts well would be a Shigefusa--thick, and cuts with primo efficiency, because Iizuka san has nailed the profile, distal taper, balance point and face grind. A thick knife that cuts like crap would be a Farberware--thick in the back, poorly ground, and not matter how you sharpen it, it will always cut like crap. Compare that Farberware to a Tojiro DP, which has a simple grind and bad balance, and the Tojiro will out perform the Farberware even when dull--simply because it is thinner.

There are factors to a knife other than cutting power, but when it comes to that, the CCK 1303 is a bang-for-the-buck MONSTER.
i guess i shouldn't have made a reference to a knife i dont own, but i thought i remembered hearing that the CCKs are very thick behind the edge. usually when something is thick behind the edge it can be really sharp but not perform as well. this was the point i was trying to make with that comparison. i guess another way to describe what i mean is any single bevel knife. the thickness of that knife at the spine vs. the edge is a completely different story to how sharp and refined the actual edge is

i understand what you are saying and thats why i "kinda disagree" but around here, it is not really defined what sharp actually means. my only point was that to me, sharpness is the actual edge and performance is something completely different, just like how you described your CCK
 

Eamon Burke

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i guess i shouldn't have made a reference to a knife i dont own, but i thought i remembered hearing that the CCKs are very thick behind the edge. usually when something is thick behind the edge it can be really sharp but not perform as well. this was the point i was trying to make with that comparison. i guess another way to describe what i mean is any single bevel knife. the thickness of that knife at the spine vs. the edge is a completely different story to how sharp and refined the actual edge is

i understand what you are saying and thats why i "kinda disagree" but around here, it is not really defined what sharp actually means. my only point was that to me, sharpness is the actual edge and performance is something completely different, just like how you described your CCK
I see what you are saying, and I can't say it is directly wrong, since "sharp" is such a vague term. I would have to say, however, that in any circles other than those of knife enthusiasts, referring to an edge as "sharp" can work. I've found that there isn't any one clear type of sharp, I don't see edges as crappy or good anymore, only different, and I judge them by how intentional I can tell they were put there, so lumping the different types of working edges into one category can be a little onerous when folks are learning and minutiae are being discussed.



Oh and CCKs are SUPER thick spine at the handle, but they are insanely thin, if you consider it a ratio from surface area to thickness. They performance of a huge sheet of steel is actually surprising--they may seem like they were knocked together, but they are quite an elegant solution.
 
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