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- Jul 28, 2013
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One method of calculating slicing resistance
On a knife blade with flat sides that taper gradually from spine to edge, the ratio between spine thickness and blade height, measured at the middle of the spine halfway between grip and point, helps to define the shape of the wedge and thus reveals a good deal about the amount of slicing resistance to be expected.
After dividing spine thickness by blade height, what one should be looking for in a good kitchen slicer is a ratio that does not exceed 0.08. The smaller that ratio is, the less resistance the blades wedge will create while slicing.
Here are four examples:
1. The F. Dick 1787 Chefs Knife with a 23 cm blade, a really fine slicer, has a spine thickness of 1.8 mm and a blade height of 42 mm, which amounts to a slicing resistance ratio (can we call it SRR?) of 0.043 (1.8 ÷ 42 = 0.043).
2. The Wüstof Classic 23 cm cook's knife, also a great performer in the kitchen, has a spine thickness of 2.4 mm and a blade height of 44 mm, thus it weighs in at SRR 0.055 (2.4 ÷ 44 = 0.055).
3. My wonderful Marbles hunting knife from the 1950s, one with a 10 cm blade, has a spine thickness of 3.7 mm and a blade height of 24 mm, giving us a slicing resistance ratio of 0.154 (3.7 ÷ 24 = 0.154). As I mentioned, anything above 0.08 is going to resist traveling through vegetables more than will please the average cook, and this applies to the Marbles.
4. My 1970s J.A. Henckels Nicker, a German hunting knife with a traditional form developed long ago for severing the spine of a wounded wild boar, has an 11.4 cm blade, a 5 mm spine thickness and a 20 mm blade height, which translates to 0.25 on this scale (5 ÷ 20 = 0.25). As the number indicates, this knife is a genuine wedge, has high slicing resistance and its geometry comes closer to resembling an axe than a kitchen knife, which of course it is not. Use this to slice onions while out in the woods and you will marvel at the drag. It can be and is done, but if there were such a thing as a Slicing Joy Ratio (SJR), this knife, magnificent as it is, would come in close to last place.
One could calculate all this in reverse, divide height by spine thickness, and the numbers created that way would also tell a story about resistance, but in inverse order: the lower the number, the higher the resistance. When done that way, a figure around 20 or higher would define a good slicer. There are also ways to use three figures (spine thickness and both sides of the blade) to calculate a triangle and, in the end, arrive at the angle from edge to spine. That, however, requires a dose of trigonometry and much more time.
I prefer the first method mentioned above, dividing spine thickness by blade height at the center of the spine. That way, any low-resistance knife will begin with a crisp 0.0..., and the lower the number, the lower the resistance. Other kitchen knives I have used that behave well when working on vegetables have slicing resistance ratios between 0.075 and 0.033. There are, however, limits to this. If it gets too low, like below 0.03, there will be issues with blade stability, and anything above 0.1, as seen in the last two examples above, will cause problems trying to squeeze itself through carrots and onions. A knife with a slicing resistance ratio of 0.2 or higher is better suited for hunting or commando raids.
This is not the only factor that determines slicing resistance; above all, blade smoothness and blade shape must also be considered. Polishing the sides of a blade with a good metal polish will help any knife to slice easier. As far as shape is concerned, a thicker blade with a pronounced point (as opposed to a traditional Chinese cooks knife, a rectangle when viewed from the side) being pulled across a slicing board with handle held high, will work its way through vegetables somewhat easier than would normally be expected simply because the height of the blade decreases toward the point, thus there is less steel on the flanks to cause drag.
This method of calculating slicing resistance applies only to blades that taper gradually from spine to edge, a very common shape among kitchen knives. A knife with a Scandinavian grind (beginning at the spine, both sides of the blade remain parallel for some distance before beginning to taper down to the edge) will have a much more pronounced wedge than its slicing resistance ratio says it has, at least when calculated using the method described above: If its wedge were to continue at the same angle from edge all the way to spine, the spine would be considerably thicker and the knife would resemble the Henckels Nicker mentioned earlier. Many of those fine single-beveled Japanese knives (flat on one side, tapered on the other) also resemble a single-sided Scandinavian grind; I have no experience with them and cannot yet say how their slicing resistance might be reflected using this method. And attempting to calculate slicing resistance with a knife sporting a hollow grind, which is intended to reduce drag by decreasing the thickness of the blade immediately above the edge, would require more knowledge of math and physics than I can offer.
I have no idea if this system of measurement has been introduced elsewhere. Ive been around knives for a very long time and have never run across anything similar to it. I came up with it without any assistance and apologize in advance if its common knowledge and if I thus appear to have stolen it from someone else, which I didnt.
I realize that most people who know knives will tend to scoff at a scale like this because an experienced eye can tell at a glance what slicing resistance will be like. Nonetheless, not everyone can be expected to have an experienced eye and there are those who like to have a number as a point of reference.
Sam
On a knife blade with flat sides that taper gradually from spine to edge, the ratio between spine thickness and blade height, measured at the middle of the spine halfway between grip and point, helps to define the shape of the wedge and thus reveals a good deal about the amount of slicing resistance to be expected.
After dividing spine thickness by blade height, what one should be looking for in a good kitchen slicer is a ratio that does not exceed 0.08. The smaller that ratio is, the less resistance the blades wedge will create while slicing.
Here are four examples:
1. The F. Dick 1787 Chefs Knife with a 23 cm blade, a really fine slicer, has a spine thickness of 1.8 mm and a blade height of 42 mm, which amounts to a slicing resistance ratio (can we call it SRR?) of 0.043 (1.8 ÷ 42 = 0.043).
2. The Wüstof Classic 23 cm cook's knife, also a great performer in the kitchen, has a spine thickness of 2.4 mm and a blade height of 44 mm, thus it weighs in at SRR 0.055 (2.4 ÷ 44 = 0.055).
3. My wonderful Marbles hunting knife from the 1950s, one with a 10 cm blade, has a spine thickness of 3.7 mm and a blade height of 24 mm, giving us a slicing resistance ratio of 0.154 (3.7 ÷ 24 = 0.154). As I mentioned, anything above 0.08 is going to resist traveling through vegetables more than will please the average cook, and this applies to the Marbles.
4. My 1970s J.A. Henckels Nicker, a German hunting knife with a traditional form developed long ago for severing the spine of a wounded wild boar, has an 11.4 cm blade, a 5 mm spine thickness and a 20 mm blade height, which translates to 0.25 on this scale (5 ÷ 20 = 0.25). As the number indicates, this knife is a genuine wedge, has high slicing resistance and its geometry comes closer to resembling an axe than a kitchen knife, which of course it is not. Use this to slice onions while out in the woods and you will marvel at the drag. It can be and is done, but if there were such a thing as a Slicing Joy Ratio (SJR), this knife, magnificent as it is, would come in close to last place.
One could calculate all this in reverse, divide height by spine thickness, and the numbers created that way would also tell a story about resistance, but in inverse order: the lower the number, the higher the resistance. When done that way, a figure around 20 or higher would define a good slicer. There are also ways to use three figures (spine thickness and both sides of the blade) to calculate a triangle and, in the end, arrive at the angle from edge to spine. That, however, requires a dose of trigonometry and much more time.
I prefer the first method mentioned above, dividing spine thickness by blade height at the center of the spine. That way, any low-resistance knife will begin with a crisp 0.0..., and the lower the number, the lower the resistance. Other kitchen knives I have used that behave well when working on vegetables have slicing resistance ratios between 0.075 and 0.033. There are, however, limits to this. If it gets too low, like below 0.03, there will be issues with blade stability, and anything above 0.1, as seen in the last two examples above, will cause problems trying to squeeze itself through carrots and onions. A knife with a slicing resistance ratio of 0.2 or higher is better suited for hunting or commando raids.
This is not the only factor that determines slicing resistance; above all, blade smoothness and blade shape must also be considered. Polishing the sides of a blade with a good metal polish will help any knife to slice easier. As far as shape is concerned, a thicker blade with a pronounced point (as opposed to a traditional Chinese cooks knife, a rectangle when viewed from the side) being pulled across a slicing board with handle held high, will work its way through vegetables somewhat easier than would normally be expected simply because the height of the blade decreases toward the point, thus there is less steel on the flanks to cause drag.
This method of calculating slicing resistance applies only to blades that taper gradually from spine to edge, a very common shape among kitchen knives. A knife with a Scandinavian grind (beginning at the spine, both sides of the blade remain parallel for some distance before beginning to taper down to the edge) will have a much more pronounced wedge than its slicing resistance ratio says it has, at least when calculated using the method described above: If its wedge were to continue at the same angle from edge all the way to spine, the spine would be considerably thicker and the knife would resemble the Henckels Nicker mentioned earlier. Many of those fine single-beveled Japanese knives (flat on one side, tapered on the other) also resemble a single-sided Scandinavian grind; I have no experience with them and cannot yet say how their slicing resistance might be reflected using this method. And attempting to calculate slicing resistance with a knife sporting a hollow grind, which is intended to reduce drag by decreasing the thickness of the blade immediately above the edge, would require more knowledge of math and physics than I can offer.
I have no idea if this system of measurement has been introduced elsewhere. Ive been around knives for a very long time and have never run across anything similar to it. I came up with it without any assistance and apologize in advance if its common knowledge and if I thus appear to have stolen it from someone else, which I didnt.
I realize that most people who know knives will tend to scoff at a scale like this because an experienced eye can tell at a glance what slicing resistance will be like. Nonetheless, not everyone can be expected to have an experienced eye and there are those who like to have a number as a point of reference.
Sam
