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I Understand but....
- Thread starter akee
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A chisel grind knife is designed to be a directional cutter, for example a sushi knife is chisel ground on the right side of the blade for a right handed person to help the thin slices fall away from the blade easier. When cutting material like a plastic bottle the knife will not cut straight, the single sided grind pushes the blade to the left.
A symmetrical grind will not have a right or left haded perferance nor will it push one way or the other in the plastic bottle test. However it will not shed thin sliced fish from the blade as well as a chisel grind either. The steepness of the one sided grind is what makes the shedding of thin slices easier.
The sharpening will be no more difficult with one over the other except that the chisel is sharpened on one side only. From a geometric standpoint both edges have the same total included angle so strength should be equal.
A symmetrical grind will not have a right or left haded perferance nor will it push one way or the other in the plastic bottle test. However it will not shed thin sliced fish from the blade as well as a chisel grind either. The steepness of the one sided grind is what makes the shedding of thin slices easier.
The sharpening will be no more difficult with one over the other except that the chisel is sharpened on one side only. From a geometric standpoint both edges have the same total included angle so strength should be equal.
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What knife (or knives) are thinking about, specifically?
If you're talking about a "tactical" folder, an asymetrical grind is probably a comprimise between control (symetrical) and ease of sharpening/manufactur (chisel). You'll often see this on partially serrated knives. I know Kershaw and CRKT do this a lot. I imagine the reason these manufactures do it these ways is to maximize control. An entirely chisel-ground knife of that type (all-around use pocket folder) would lose some of its usefulness (read the post above). If the serrations remained chisel-ground (which is how they usually are), but the plain section was symetrical, the blade would make 2 very seperate cuts. Having an asymetrical grind lessens the gap between cutting planes.
For unserrated folders, I'd imagine it was done simply for ease of sharpening. The Surefire Alpha is asymetrically ground. Emersons are (mostly) chisel ground. These knives aren't really intended for "every day" use. Often Emersons that are used for daily tasks will eventually become asymetrically edged simply because of the method required to sharpen them. 99% of the sharpening is done to the normal edge until a burr forms, then the other edge is touched upon to remove the burr. After much use, it's likely that the opposite side will become ground some itself. This happened to me with a couple Spydercos. They are no less dull than they were before, just the "factory" edge is long since been altered.
EDIT: OK, my reply got crossposted with your clarification, but I'm still not sure what you mean. A specific example of a knife would help.
If you're talking about a "tactical" folder, an asymetrical grind is probably a comprimise between control (symetrical) and ease of sharpening/manufactur (chisel). You'll often see this on partially serrated knives. I know Kershaw and CRKT do this a lot. I imagine the reason these manufactures do it these ways is to maximize control. An entirely chisel-ground knife of that type (all-around use pocket folder) would lose some of its usefulness (read the post above). If the serrations remained chisel-ground (which is how they usually are), but the plain section was symetrical, the blade would make 2 very seperate cuts. Having an asymetrical grind lessens the gap between cutting planes.
For unserrated folders, I'd imagine it was done simply for ease of sharpening. The Surefire Alpha is asymetrically ground. Emersons are (mostly) chisel ground. These knives aren't really intended for "every day" use. Often Emersons that are used for daily tasks will eventually become asymetrically edged simply because of the method required to sharpen them. 99% of the sharpening is done to the normal edge until a burr forms, then the other edge is touched upon to remove the burr. After much use, it's likely that the opposite side will become ground some itself. This happened to me with a couple Spydercos. They are no less dull than they were before, just the "factory" edge is long since been altered.
EDIT: OK, my reply got crossposted with your clarification, but I'm still not sure what you mean. A specific example of a knife would help.
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You can read on the Y2K's link below for the reason this particluar knife is designed the way it is.
The reason, apart from clean lines (humans just tend to like symetrical things) most knives are symetrical is because it's the best all-around cutter. The majority of cutting tasks I perform work best with a symetrically ground knife (both the blade, and the edge).
For specialty knives (like sushi knives or other chef's blades), an asymetrically ground blade (and edge) may indeed work better. For example, a blade that is completely flat ground (all the way to the edge) on one side, and hollow ground with a chisel edge on the other makes a great chef's knife. The flat side faces towards the user, and cuts straight down. The hollow grind reduces surface contact and therefore resistance, and the chisel edge pushes the food away for the next cut.
The reason, apart from clean lines (humans just tend to like symetrical things) most knives are symetrical is because it's the best all-around cutter. The majority of cutting tasks I perform work best with a symetrically ground knife (both the blade, and the edge).
For specialty knives (like sushi knives or other chef's blades), an asymetrically ground blade (and edge) may indeed work better. For example, a blade that is completely flat ground (all the way to the edge) on one side, and hollow ground with a chisel edge on the other makes a great chef's knife. The flat side faces towards the user, and cuts straight down. The hollow grind reduces surface contact and therefore resistance, and the chisel edge pushes the food away for the next cut.
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Asymmetrical bevels come from the Japanese kitchen cutlery industry. Traditional Japanese kitchen knives, as you know, are single bevel. This makes them easy to sharpen and easy to develop the very acute angles that the hard steel they employ make possible. While it makes controlling the knife a little more challenging, it does provide for very thin cuts - something that's more common in Japanese cooking than in Western cooking.
When the Japanese started making Western style knives,the natural tendency was to make one that, while double beveled, would still lend itself more readily to making very thin slices. So the asymmetrical bevels came about that way. There is no advantage other than an ability to make a slightly thinner slice than a symmetrically beveled knife. The only disadvantage is that it will only make a thinner slice when the longer bevel is on the outside. So the knives become right or left handed to that extent. I don't see an advantage (or disadvantage) in a tactical knife at all, only in a knife intended to make thin slices.
Some Japanese Wetern kitchen knives have a flatter (but not flat or concave) inside to the blade with a more convex outside. They still have double bevels but, with that type of design get slightly thinner slices. Most are not, though. Most are symmetrical in terms of the sides of the blade and only asymmetrical in the grinding of the bevels.
When the Japanese started making Western style knives,the natural tendency was to make one that, while double beveled, would still lend itself more readily to making very thin slices. So the asymmetrical bevels came about that way. There is no advantage other than an ability to make a slightly thinner slice than a symmetrically beveled knife. The only disadvantage is that it will only make a thinner slice when the longer bevel is on the outside. So the knives become right or left handed to that extent. I don't see an advantage (or disadvantage) in a tactical knife at all, only in a knife intended to make thin slices.
Some Japanese Wetern kitchen knives have a flatter (but not flat or concave) inside to the blade with a more convex outside. They still have double bevels but, with that type of design get slightly thinner slices. Most are not, though. Most are symmetrical in terms of the sides of the blade and only asymmetrical in the grinding of the bevels.