Understanding Distal Taper

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Kippington

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There's a lot of variation in kitchen knives when it comes to distal taper. The topic tends to get glossed over and the details get heaped into one narrow definition, so hopefully this thread will help explain some of the more subtle characteristics of a good taper.

First we should cover what taper looks like from the spine. It can be broken up into three sections - The grip area, the middle of the blade and the tip.

Grip (neck, choil and handle) area

The grip area, or the part of the blade that goes into the handle is the first part we should pay attention to with regards to taper. It's often measured as the spine thickness of the neck, or the thickness of the spine above the heel.

There are three reasons why you would want this to be the thickest part of the blade, the first being comfort. A thicker spine is more comfortable to hold as it allows for more surface area to push down on with your hand. Many cheaper knives (such as Kiwi knives) have extremely thin spines in this area. These make it uncomfortable to push down while cutting through harder foods, as all the force going back up into your hand gets concentrated through a narrow surface.
Similarly, the thickness of the choil down to the cutting edge will influence the comfort of your finger in that area during forward push-cuts. The dreaded Wusthof/Sabatier style full-bolster was designed specifically for this reason, to expand the choil area and increase the thickness where you grip the knife. Other knives will reverse this idea, and have the spine thickness drop dramatically where your finger goes into the choil, while still maintaining a high degree of thickness at the neck.
A full bolster maintaining neck thickness down the choil, plus an example of the reverse

Another reason is strength: Many cheaper mass-manufactured knives will have the neck thickness the same as the spine above the heel of the blade. This creates a stress riser at the neck - on thin knives in particular - where the knife is weaker and more flexible at the neck when compared to the stiffer heel and handle on either side of it. Jobs such as crushing garlic with the side of your knife will concentrate forces into the neck, making it more likely to bend in the case of a san-mai/honyaki or crack with a fully hardened blade.

The last reason applies mostly to hidden tang knives with no bolster. A hidden tang can only be is thick as the spine going into the handle, and we want the thickest tang we can possibly get to help increase strength and mitigate any rust that may have been caused by moisture getting into the handle. A thicker neck/spine helps facilitate this improvement, which in turn increases the lifespan of the knife.
Carbon steel knives are more susceptible to rust, but stainless knives are definitely not immune to this phenomenon. A rusty hidden tang, particularly a thin one, is a disaster waiting to happen.
Now it could be argued that some of these points are not part of the distal taper and have more to do with the handle. However, understanding the thickness at this junction helps to explain why distal taper further down the blade is considered to be a positive attribute in kitchen knives.

Middle area

So taking everything above into consideration, it would seem like we want a super thick spine, right? Well no, obviously a thick a blade will easily get wedged in food during a cut. Naturally we want something thinner in the area where we do the cutting, so we'll need to transition the thick spine of the handle area into a thinner middle section of the blade. There are many ways to do this, it can be done drastically or gradually, and through concave, convex or linear means. We can also use a combination of any of these three methods to create a compound taper.
(a) No taper and the thinnest grip area of the four, (b) straight/linear taper, (c) concave taper, (d) convex taper

As with all things relating to knives, there's a balancing act going on with taper in the middle of the blade. Any positives you might get out of one style will probably increase a negative property, depending on how you look at it. There are four things to take into consideration: Food separation, food release, flexibility and balancing point.

Thinner cross-sections (in conjunction with the grind) can have better food separation and possibly improved food release over a thicker one - more on that below. That said, thinning the cross-section of a knife requires the removal of steel which in turn increases flexibility and removes weight. This can count as a negative thing for some people, as the removal of too much steel can cause a knife to feel whippy and flimsy, as well as sending the centre of balance back towards the handle. Some makers mitigate this by forming a taper at the grip until the blade reaches a certain thickness, then stopping the taper altogether to form an essentially taper-free blade from the middle to the tip. This is an example of one of the many variations of a compound taper, and Kato's style is a good showcase of this.

Tip area

For gyutos, the way a taper ends at the tip is very simple - The thickness of the spine transposes into the grind at the area where they meet. Some people reference sideways slices (e.g. parallel cuts to the board on onions) with the tip of the knife as an indicator for good taper, but really the thinness of the grind is the thing doing the work. You could also use a nakiri to do the same sideways cuts, only the tip of the knife doesn't end at a point. It should be said, having a point can help due to having less surface area in contact with the food, and the lower blade height at the tip means the average thickness of the grind goes down as the spine heads towards the edge, but this doesn't have as much to do with the taper as it does the grind and profile shape.

One important thing to note is that knives with super thin tips will have a lot of flexibility in that area. Some people really dislike any flexibility at all, others don't notice it and might even prefer it for it's related positive attributes (e.g. thinness for sideways cuts).
You can actually test how thin the tip of a knife is by balancing the knife on your finger just behind the centre of mass towards the handle and allowing the tip of the knife to bounce off a hard surface. Thicker tipped knives will clunk but the thinner ones will bounce, giving a surprisingly good indication of how well a knife will perform during the sideways cut.

Taper and balancing point

There are many things that determine the balancing point of a knife, and taper can be one of the more influential factors. If you prefer knives with more forward balance (towards the tip) you'd do well to look for knives with taper that maintains thickness from the neck into the middle of the blade. People that prefer handle-balance should go for extreme taper, and there's obviously an endless amount of possibilities of anything in-between.

Taper and grind/food release

We hear people say that a choil shot can often be an inaccurate representation of the grind of a knife, and the presence of a taper is one of the reasons why.

Here is an example of four grinds, each with the same angle at the edge. They may look very different, but it's possible to have all of the four cross-sections occur at different points across the same tapered bar of steel.
The first one on the left is essentially a full-flat grind, known for some of the worst food release possible. As we move right you can see the spine getting thinner, which causes the shinogi line to move down the blade. The example on the far right is where the spine is quite thin and the shinogi has moved down near the bottom of the blade. As you might imagine, the ability for food to stick to the smaller bevel decreases with the shrinking area of contact. This means that the far right example has both better food release and less wedging in food. It's difficult to argue against two advantages like that, so some knife makers create a thick spine in the handle area and drastically shrink it way down as soon as it's out of the grip of your hand. This would be another example of compound taper.

So, that pretty much covers it.
Thanks for reading guys. let me know if you have any questions.
 
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labor of love

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I’ve often wondered if there is an ratio for ideal distal taper. Should a knife regardless of thickness above the choil be 10x, 15x or 20x thinner 1cm from the tip?
Even though we don’t have a universal ideal, maybe using a ratio can help with classification of the extremity of the taper, right?
 

Kippington

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I’ve often wondered if there is an ratio for ideal distal taper. Should a knife regardless of thickness above the choil be 10x, 15x or 20x thinner 1cm from the tip?
Even though we don’t have a universal ideal, maybe using a ratio can help with classification of the extremity of the taper, right?
It's a cool idea, but I don't think you can scale the ratio up or down like that. The ideal taper on a thicker knife might cause an unusable tip on a thinner knife if made to the same ratio.
 

Barmoley

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Great write up. I am glad you pointed out balance effect of distal taper, this is an often overlooked area when people talk about distal taper.
 

Corradobrit1

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I’ve often wondered if there is an ratio for ideal distal taper. Should a knife regardless of thickness above the choil be 10x, 15x or 20x thinner 1cm from the tip?
Even though we don’t have a universal ideal, maybe using a ratio can help with classification of the extremity of the taper, right?
Probably too many variables but I bet there are some fairly good guidelines that can be gleaned from such a formula. I now have a better appreciation of my Kato's and the decision making that was taken to arrive at the various Standard and WH styles. For Wa handle knives the thick spine is far more comfortable. It appears Will Catcheside has given this some thought too.

Excellent writeup.
 

labor of love

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Are you saying that thicker knives have more room at the spine for larger ratios? And applying these larger ratios to thinner spines(at the choil) would produce a tip that’s just too thin?
If so, I agree. The most recent mazaki batch had a 5.75-6mm spine at the choil. But then at the tip was very thin. Whatever ratio the knife had couldn’t be replicated with a 3.5mm spine over choil. But to me, this is an example of too much distal taper. My shigehiro gyuto also has quite the workhorse spine, but it feels like a workhorse in cutting from spine above choil to the tip, but with distal taper.
 

captaincaed

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So what runs through your head when you see a super thick tang such as a Jiro? I imagine future thinning would affect the balance quite a lot. Anything else stand out?

Also true on the Kiwi. Lived in Thailand for a while and kept some around. Even tried to round the spine for comfort. Ultimately got rid of every one. They make great Som Tam but damn they're hard to get used to after using better Japanese knives.

Mazaki is killing it in the taper department. I think it's one of the best grind and taper combos for the price right now
 

labor of love

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I’m probably in the minority here. Lots of people probably do want a tip ground to a particular thinness without regard to spine thickness over the heel.
My thinking is that I ultimately favor a heavier knife to cut like such from heel to tip. Which is why I think a ratio of some sort would help me understand my own preferences.
 

Barmoley

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I prefer a heavier and stiffer knife too. The problem I have with extreme taper is that the knife changes the way it cuts depending on which portion of the blade is used. If the extreme taper is uniform through the blade the portion closer to the handle has a drastically different grind than the middle. You could get a two knives in one type of a situation, which some might like, but I prefer consistency through most of the length of the blade. This is not very noticeable when the taper is not extreme or when spine and blade closer to the edge taper at different rates.
 
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SeattleBen

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Thank you for the clear and concise write up. I'll also throw in for the appreciation of non hand drawn drawings as being more clear.
 

ian

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I’m probably in the minority here. Lots of people probably do want a tip ground to a particular thinness without regard to spine thickness over the heel.
My thinking is that I ultimately favor a heavier knife to cut like such from heel to tip. Which is why I think a ratio of some sort would help me understand my own preferences.
As you say, there's no ideal notion for distal taper, since it depends on user preference. But part of the problem with using a single ratio even to classify taper is that you have to decide where to measure. A single number (basically, the slope of the taper) would work if the taper was always linear, but it's hard to capture the shape of an arbitrary paper with a single number. The usual set of 4 numbers is useful, though.

Here are a bunch of example measurements from JKI. I'll include width of spine at handle/heel/middle/1cm from tip, in order, and in mm. All 240mm gyutos.

Gengetsu: 3.85, 3.23, 1.78, .51
Kochi Migaki: 3.93, 3.47, 2.48, 1.08
Kochi KU: 5.15, 3.9, 2.1, .8
Heiji: 4.17, 3.73, 2.55, 1.53
Ginga: 2.23, 2.23, 1.96, .75
Ginrei (Shihan): 3.38, 3.07, 2.85, 1.21
Kagekiyo (Wh #2): 3.62, 3.79, 2.88, .69
Uraku (Stainless): 2.45, 2.45, 2.22, 1
Hinoura (Ajikataya): 4.7, 3.39, 2.74, 1.81
Blazen Ryusen: 3.66, 3.43, 1.9, .91
Ittetsu (Wh #2): 3.49, 3.47, 2.82, 1.57

Just from these numbers you can tell what the shape of the taper looks like.
 
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labor of love

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But, if you notice the knives with the most dramatic distal taper from spine above heel to mid point of blade are also the same knives with the most dramatic taper from spine above heel to tip.
To me this means the mid point measurement is simply obeying the distal taper that is decided by the ratio between tip thinness and above the heel thickness so I concern myself more with those 2 measurements
 

labor of love

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My contention is that perhaps knowing a ratio between spine thickness at heel and tip for our favorite knives may lead to some insight into knowing which knives might be our favorite knives (on a personal level) and why that may be.

Hope I didn’t derail a great thread.
 

M1k3

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Great write up and pictures. Looking forward to the one on grinds and profiles ;)
 
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Corradobrit1

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I prefer a heavier and stiffer knife too. The problem I have with extreme taper is that the knife changes the way it cuts depending on which portion of the blade is used. If the extreme taper is uniform through the blade the portion closer to the handle has a drastically different grind than the middle. You could get a two knives in one type of a citation, which some might like, but I prefer consistency through most of the length of the blade. This is not very noticeable when the taper is not extreme or when spine and blade closer to the edge taper at different rates.
Theres a subtle inflection in the grind of the Kato WH towards the thickest part near the handle just in front of the choil. Impossible to see in pics but easily picked out when manipulated in the right light. This helps to retain a far more modest taper along the blade road in the lower portion of the convex grind above the edge.
 

ian

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My contention is that perhaps knowing a ratio between spine thickness at heel and tip for our favorite knives may lead to some insight into knowing which knives might be our favorite knives (on a personal level) and why that may be.

Hope I didn’t derail a great thread.
I think this is on topic! I also think that the ratio of spine thickness at the heel to spine thickness at the middle is a good number to look at. It just doesn’t capture the full picture. Here’s an updated spreadsheet:

IMG_1422.jpg


(The above is a picture I took with my phone of a screenshot I took on my computer. What do you want... I was in a rush and confused.)

Above, I’ve included not just the thicknesses in mm, but the ratios between the various thicknesses. The knives are ordered by the heel/middle thickness, ie your measure of taper.

Some takeaways:

1) Gengetsu and Kagekiyo have screaming thin tips. The taper from middle to tip is much more dramatic than from heel to middle. Note the huge difference in middle/tip vs heel/middle. Also, the Kagekiyo doesn’t even have a huge taper heel/middle... it’s middle of the road in that respect, even though the final taper is the most extreme of all. On the other end, Heiji has a fair bit of heel/middle taper, but not much middle/tip taper.

2) Most tapers aren’t actually linear all the way to the tip. The Heiji is maybe the closest, but middle/tip is always bigger than heel/middle. Of course, maybe it could be linear up till 2 cm from the tip or something, but that’s not included in the data. It would be nice to have more measurements for each knife.

In any case, though, if you look at the spreadsheet, there’s not much relationship between the second to last column and the last column. Again, though, maybe all this says is that people often grind the tips thinner no matter what, and when we’re talking about “taper” we should more be talking about what happens in the first 210mm of the knife, rather than at the tip.
 

Nemo

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Great write-up Kip.

But you didn't need to break your mate's knife just to demonstrate a stress riser [emoji16].
 

labor of love

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I couldnt disagree more! I guess we're just concerned about different things. The difference in spine thickness at middle blade could vary quite abit, but what im saying is that .5mm difference is a much profound thing at the tip than at the mid point. But should we disregard mid blade thickness? Nah, but I keep it on the back burner.
When we talk about "good distal taper" we're implying there is a good bit of distal taper happening therefore heel area of the blade will be beefier right? And the tip area will be thin right?

So Gengetsu and Kagekiyo have screaming thin tips? But what kind of cutting experience would those gyutos have if they are 5mm thick at the heel? The weight of the blade wouldve shifted quite abit to the rear of the blade. Can the weight of a heavier blade create more force on the tip area and make the tip area fragile if the tip area is crazy thin? Yep. So with keeping a good distal taper but also keeping a tip away from being fragile theres something there, a balancing act.
Maybe, a ratioo_O

But all this talk about distal taper with regard to spines is kinda of isolating. Much of what happens with cutting and feel has more to do with how weight, grind, measurements relate, how it all relates.

Im using distal taper discussion as a proxy for weight distribuition in some ways, also I just dont like workhorse knives with laser tips :)
 

ian

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I couldnt disagree more! I guess we're just concerned about different things. The difference in spine thickness at middle blade could vary quite abit, but what im saying is that .5mm difference is a much profound thing at the tip than at the mid point.
Absolutely!
But should we disregard mid blade thickness? Nah, but I keep it on the back burner.
Not so sure about this. If you only have 3 measurement points, I feel like middle of the blade thickness will more accurately reflect what’s happening in most of the knife than thickness at the heel or tip.
When we talk about "good distal taper" we're implying there is a good bit of distal taper happening therefore heel area of the blade will be beefier right? And the tip area will be thin right?

So Gengetsu and Kagekiyo have screaming thin tips? But what kind of cutting experience would those gyutos have if they are 5mm thick at the heel? The weight of the blade wouldve shifted quite abit to the rear of the blade. Can the weight of a heavier blade create more force on the tip area and make the tip area fragile if the tip area is crazy thin? Yep. So with keeping a good distal taper but also keeping a tip away from being fragile theres something there, a balancing act.
Maybe, a ratioo_O
Agreed!
But all this talk about distal taper with regard to spines is kinda of isolating. Much of what happens with cutting and feel has more to do with how weight, grind, measurements relate, how it all relates.

Im using distal taper discussion as a proxy for weight distribuition in some ways, also I just dont like workhorse knives with laser tips :)
Yea, me neither. I actually found it disconcerting to use one beefy Mazaki I had for this reason (and other reasons).

I’m sorry, I must have misinterpreted what you were saying previously. All I was saying above is that you can’t rate distal tapers based on one number like (heel thickness / middle thickness), or (heel thickness / tip thickness), and that it’s more complex than that. This is what Kip is saying too, I guess, when he talks about the different types.

It was interesting to see all the data in the table together, though!
 
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