|
Post by greatsaiyaman888 on Oct 28, 2015 17:17:58 GMT
Right, but on a properly profiled convex grind you can vary the angle all the way from the hira to the ha. Something you can't do on a flat grind because there's not much angle left to change. It's just one acute angle from hira to ha on a flat grind.
|
|
|
Post by DigsFossils-n-Knives on Oct 28, 2015 17:23:55 GMT
Right, but on a properly profiled convex grind you can vary the angle all the way from the hira to the ha. Something you can't do on a flat grind because there's not much angle left to change. It's just one acute angle for hira to ha on flat grind. Let me first say that I don't have any skills regarding cutting with a katana. What do you mean by vary the angle? Do you mean that the thicker niku (larger convex) gives you more angles to cut than the no niku (flat ground) blade?
|
|
|
Post by Kiyoshi on Oct 28, 2015 17:24:49 GMT
But any non negative angle variance from a straight line will cause a wider entry angle, thus causing drag, making softer targets harder to cut. Even if it isn't much, it is a nonzero difference. I can lay the argument out formally if need be.
|
|
|
Post by greatsaiyaman888 on Oct 28, 2015 17:39:45 GMT
Right, but on a properly profiled convex grind you can vary the angle all the way from the hira to the ha. Something you can't do on a flat grind because there's not much angle left to change. It's just one acute angle for hira to ha on flat grind. Let me first say that I don't have any skills regarding cutting with a katana. What do you mean by vary the angle? Do you mean that the thicker niku (larger convex) gives you more angles to cut than the no niku (flat ground) blade? What I mean is that because it's a convex grind, the grind angle constantly changes from the hira right down to the edge. It's not just 20 degrees or 45 degrees all the way, rather the angles can be 50,47,43,35,30,28 as a rough example on a convex grind. They can be more acute or wider, it varies how you do it. Most production blades that have niku get the convex shape but not good cutting angles and generally don't match on both sides.
|
|
|
Post by greatsaiyaman888 on Oct 28, 2015 17:45:39 GMT
But any non negative angle variance from a straight line will cause a wider entry angle, thus causing drag, making softer targets harder to cut. Even if it isn't much, it is a nonzero difference. I can lay the argument out formally if need be. If done properly it shouldnt cause drag but the opposite as the convex shape pushes the target away from the blade on both sides as it passes through.
|
|
|
Post by DigsFossils-n-Knives on Oct 28, 2015 17:47:19 GMT
What I mean is that because it's a convex grind, the grind angle constantly changes from the hira right down to the edge. It's not just 20 degrees or 45 degrees all the way, rather the angles can be 50,47,43,35,30,28 as a rough example on a convex grind. They can be more acute or wider, it varies how you do it. Most production blades get the convex shape but not good cutting angles and generally don't match on both sides. So what does this mean in terms of cutting? Does the the convex or full niku give you more angles to cut with, or more forgiving regarding blade alignment?
|
|
|
Post by greatsaiyaman888 on Oct 28, 2015 17:47:55 GMT
What I mean is that because it's a convex grind, the grind angle constantly changes from the hira right down to the edge. It's not just 20 degrees or 45 degrees all the way, rather the angles can be 50,47,43,35,30,28 as a rough example on a convex grind. They can be more acute or wider, it varies how you do it. Most production blades get the convex shape but not good cutting angles and generally don't match on both sides. So what does this mean in terms of cutting? Does the the convex or full niku give you more angles to cut with, or more forgiving regarding blade alignment? Cmon Digs, you're a knife guy. I know you know what I mean. Why don't you chime in and give us your experience?
|
|
|
Post by Kiyoshi on Oct 28, 2015 17:57:35 GMT
But any non negative angle variance from a straight line will cause a wider entry angle, thus causing drag, making softer targets harder to cut. Even if it isn't much, it is a nonzero difference. I can lay the argument out formally if need be. If done properly it shouldnt cause drag but the opposite as the convex shape pushes the target away from the blade on both sides as it passes through. It's really, really simple. More angle = more drag because there is more mass at the point of displacement. Having a convex angle near the edge CANNOT make the angel smaller. The smallest non-concave angle will always be the most direct one. A line from one point to another. The only way to make the angle more acute is to raise the shinogi or remove it all together (hira zukuri) or make the angle concave. The way you suggest, a gradual convex curve, WILL NOT under any real circumstances make the angle more acute. It WILL make it larger. Unless you can prove to me how you can make a number, any given number, plus and other non-negative, non-zero number whole number add together to make a number less than or equal what you started with, or you prove that more mass and surface area somehow causes less drag (ie, why a hammer would cut batter than a razor), then you cannot be correct in your theory. It isn't a matter of correctly made, it is a matter of physics and engineering. Edit: All cuts push things away from the blade. That's what a cut is. A convex blade must push more stuff away closer to the entry point. It's displacement angle will b e larger. That is not something one can magically fix with gradual angles or anything for the above reasons.
|
|
|
Post by greatsaiyaman888 on Oct 28, 2015 18:24:04 GMT
You just explained it yourself. A convex grind pushes the cut material away from the surface of blade and clears the back of the grind. A flat grind doesn't and drags the material along the blade...you've got it backwards.
|
|
|
Post by DigsFossils-n-Knives on Oct 28, 2015 18:26:29 GMT
So what does this mean in terms of cutting? Does the the convex or full niku give you more angles to cut with, or more forgiving regarding blade alignment? Cmon Digs, you're a knife guy. I know you know what I mean. Why don't you chime in and give us your experience? My experience is that the medium being cut has a lot to do with the needed edge geometry. Flesh (like a ham without bone) slices easily yet wood tends to "grab the blade". I tend to see the convex blade do a better job chopping through wood because a flat ground blade gets stuck in the wood all the time (flat ground gets a much deeper cut though). Better yet is a flat ground blade with a secondary bevel. And I'm not speaking of splitting the wood like a splitting maul but actual cutting and chopping. When slicing/cutting paper, I also know that a blade with a convex geometry has a limited slicing angle, same for a flat ground blade with a secondary bevel. While a blade that is flat ground can slice through paper without perfect edge alignment or slice though paper with a wider range of angles. I don't cut bottles, tatami mats, or bamboo. I use 2x4s, tree stumps, and paper. So I'm asking you katana guys what your experiences are. I think the katana with niku requires more edge alignment to get a straight cut, but if the alignment is off then the edge is spared. Conversely, I think the katana with no niku doesn't requires more edge alignment to get a straight cut, but if the alignment is off then the edge/blade will bend.
|
|
|
Post by Kiyoshi on Oct 28, 2015 18:33:17 GMT
Cmon Digs, you're a knife guy. I know you know what I mean. Why don't you chime in and give us your experience? My experience is that the medium being cut has a lot to do with the needed edge geometry. Flesh (like a ham without bone) slices easily yet wood tends to "grab the blade". I tend to see the convex blade do a better job chopping through wood because a flat ground blade gets stuck in the wood all the time (flat ground gets a much deeper cut though). Better yet is a flat ground blade with a secondary bevel. And I'm not speaking of splitting the wood like a splitting maul but actual cutting and chopping. When slicing/cutting paper, I also know that a blade with a convex geometry has a limited slicing angle, same for a flat ground blade with a secondary bevel. While a blade that is flat ground can slice through paper without perfect edge alignment or slice though paper with a wider range of angles. I don't cut bottles, tatami mats, or bamboo. I use 2x4s, tree stumps, and paper. So I'm asking you katana guys what your experiences are. I think the katana with niku requires more edge alignment to get a straight cut, but if the alignment is off then the edge is spared. Conversely, I think the katana with no niku doesn't requires more edge alignment to get a straight cut, but if the alignment is off then the edge/blade will bend. This is the case. Niku protects the edge from damage via hard targets or bad alignment. The alignment has to be better for a clean cut. A blade with an acute angle and no niku will "bite" at just about any angle and will cut through an object even at weird angles but is often subject to the twisting motions resulting in a bend in the blade. For hard objects, the niku helps take the impact. All of the damage on a flat blade is at the point of impact and isn't really helped by anything so it chips, rolls, and so on. Cutting bamboo is considered a hard target so niku is better. On tatmi and bottles, no niku is more efficient. As you said, which does better all around is dependent on the target.
|
|
|
Post by greatsaiyaman888 on Oct 28, 2015 18:34:12 GMT
You are right in your response Digs.
|
|
|
Post by greatsaiyaman888 on Oct 28, 2015 18:36:07 GMT
My experience is that the medium being cut has a lot to do with the needed edge geometry. Flesh (like a ham without bone) slices easily yet wood tends to "grab the blade". I tend to see the convex blade do a better job chopping through wood because a flat ground blade gets stuck in the wood all the time (flat ground gets a much deeper cut though). Better yet is a flat ground blade with a secondary bevel. And I'm not speaking of splitting the wood like a splitting maul but actual cutting and chopping. When slicing/cutting paper, I also know that a blade with a convex geometry has a limited slicing angle, same for a flat ground blade with a secondary bevel. While a blade that is flat ground can slice through paper without perfect edge alignment or slice though paper with a wider range of angles. I don't cut bottles, tatami mats, or bamboo. I use 2x4s, tree stumps, and paper. So I'm asking you katana guys what your experiences are. I think the katana with niku requires more edge alignment to get a straight cut, but if the alignment is off then the edge is spared. Conversely, I think the katana with no niku doesn't requires more edge alignment to get a straight cut, but if the alignment is off then the edge/blade will bend. This is the case. Niku protects the edge from damage via hard targets or bad alignment. The alignment has to be better for a clean cut. A blade with an acute angle and no niku will "bite" at just about any angle and will cut through an object even at weird angles but is often subject to the twisting motions resulting in a bend in the blade. For hard objects, the niku helps take the impact. All of the damage on a flat blade is at the point of impact and isn't really helped by anything so it chips, rolls, and so on. Cutting bamboo is considered a hard target so niku is better. On tatmi and bottles, no niku is more efficient. As you said, which does better all around is dependent on the target. I know what Dig's means. He is correct and I find that performing straight horizontal cuts is the only angle that is more difficult to do than on a flat grind.
|
|
|
Post by Kiyoshi on Oct 28, 2015 18:36:54 GMT
You just explained it yourself. A convex grind pushes the cut material away from the surface of blade and clears the back of the grind. A flat grind doesn't and drags the material along the blade...you've got it backwards. You did not read well then. Yes, it displaces it and pushes the material away. It tries to push more material away closer to the edge. This causes resistance. Again, try using a flat object to cut compared to a thin blade. The concept is obvious. The closer one will be to the flat object (a wider angle) will have more resistance. End of story. The one closer to the fine angled edge will have less. I will just ignore all of your statements that don't have any kind of evidence or proof. Anyone can spout anything they want without proof as many times as they want, but it doesn't make them correct. Please prove proof next time. It is also not good to spread bad information to beginners.
|
|
|
Post by greatsaiyaman888 on Oct 28, 2015 18:38:42 GMT
You just explained it yourself. A convex grind pushes the cut material away from the surface of blade and clears the back of the grind. A flat grind doesn't and drags the material along the blade...you've got it backwards. You did not read well then. Yes, it displaces it and pushes the material away. It tries to push more material away closer to the edge. This causes resistance. Again, try using a flat object to cut compared to a thin blade. The concept is obvious. The closer one will be to the flat object (a wider angle) will have more resistance. End of story. The one closer to the fine angled edge will have less. I will just ignore all of your statements that don't have any kind of evidence or proof. Anyone can spout anything they want without proof as many times as they want, but it doesn't make them correct. Please prove proof next time. It is also not good to spread bad information to beginners. . Incorrect, what cause more drag at the entry is a secondary bevel on a flat grind because the shoulder of the bevel is causing even further resistance. The blades I am talking about are one single convex from edge to shinogi-ji. Have any of your katanas got the same geometry or are they all flat grind with secondary bevel? You can also get a full convex paper slicing sharp and even hair shaving sharp. It takes skill to do and unless you have experience sharpening you won't understand.
|
|
|
Post by greatsaiyaman888 on Oct 28, 2015 19:02:14 GMT
Here's a link for actual footage of a direct comparison between grinds. I'm sure Dig's will understand this demonstration on wood. The same principle applies to any cutting object.
|
|
|
Post by DigsFossils-n-Knives on Oct 28, 2015 19:15:53 GMT
In order to have a good conversation regarding edge geometry you need to define the cutting process as either a push cut (chop) or slicing (dragging). And what material you are "cutting".
And thanks for the Gavko vid. He is the guy that got me into making knives. His tutorials back then were the best around. The key point Gavko makes is that a flat grind blade has a cumulative friction along the bevel while the friction at the curve of the convex blade is less. So less resistance on a convex blade.
|
|
|
Post by Kiyoshi on Oct 28, 2015 19:23:06 GMT
Here's a link for actual footage of a direct comparison between grinds. I'm sure Dig's will understand this demonstration on wood. The same principle applies to any cutting object. First, no katana I have use a secondary bevel like that. They are straight lines from shinogi to edge. Second, no, it doesn't apply to all. Third, the video linked by the one you posted contradicts you. It claims that a hollow grind is best for slicing. When you cut with a katana, you don't chop, you slice. A blade with convex is best for chopping. Examples in life are certain kitchen knives and axes. But absolutely none of this says anything about resistance and mass. I will put out some statements. Tell me if you agree or disagree with them. 1. More mass, especially on the surface area pushing through an object causes more resistance. (eg, pushing a a 2x4 through water compared to pushing a 1/2" piece of wood). 2. A convex grind add more mass to the blade while keeping similar geometry adding strength to the blade. 3. Adding mass to an angle makes the angle wider. 4. A thinner angle results in a thinner point. 5. A wider angle results in a wider point. 6. You cannot add positive numbers to each other and get a lower number. 7. Adding material to a thin edge increases mass the near the edge. 8. A wider point of contact results in a wider distribution of force. 9. A finer point of contact results in a finer distribution of force. 10. Assuming the same mass and initial movement speed, a finer distribution of force displaces material better. 11. Assuming the same mass and initial movement speed, a wider distribution of force displaces material worse. 12. It harder to displace material if you have to displace it faster (ie, it takes more energy to displace the same material in a shorter amount of time, assuming optimal displacement conditions). 13. A wider angle must displace the same amount of material fast because its angle increases at a faster rate. 14. A finer angle must displace the same amount of material slower because it increases angle at a slower rate. So far, let me know what you agree or disagree with. If you disagree, please state why.
|
|
|
Post by greatsaiyaman888 on Oct 28, 2015 19:49:39 GMT
In order to have a good conversation regarding edge geometry you need to define the cutting process as either a push cut (chop) or slicing (dragging). And what material you are "cutting". And thanks for the Gavko vid. He is the guy that got me into making knives. His tutorials back then were the best around. The key point Gavko makes is that a flat grind blade has a cumulative friction along the bevel while the friction at the curve of the convex blade is less. So less resistance on a convex blade. This is true. With regards to yours and Kiyoshi's, it is negligible whether it is a push or draw cut when the edge is sharp and we are making comparisons on soft targets, (exception being very fine material like hair) unless we were cutting wood which we don't with katanas.
|
|
|
Post by greatsaiyaman888 on Oct 28, 2015 19:53:52 GMT
Here's a link for actual footage of a direct comparison between grinds. I'm sure Dig's will understand this demonstration on wood. The same principle applies to any cutting object. First, no katana I have use a secondary bevel like that. They are straight lines from shinogi to edge. Second, no, it doesn't apply to all. Third, the video linked by the one you posted contradicts you. It claims that a hollow grind is best for slicing. When you cut with a katana, you don't chop, you slice. A blade with convex is best for chopping. Examples in life are certain kitchen knives and axes. But absolutely none of this says anything about resistance and mass. I will put out some statements. Tell me if you agree or disagree with them. 1. More mass, especially on the surface area pushing through an object causes more resistance. (eg, pushing a a 2x4 through water compared to pushing a 1/2" piece of wood). 2. A convex grind add more mass to the blade while keeping similar geometry adding strength to the blade. 3. Adding mass to an angle makes the angle wider. 4. A thinner angle results in a thinner point. 5. A wider angle results in a wider point. 6. You cannot add positive numbers to each other and get a lower number. 7. Adding material to a thin edge increases mass the near the edge. 8. A wider point of contact results in a wider distribution of force. 9. A finer point of contact results in a finer distribution of force. 10. Assuming the same mass and initial movement speed, a finer distribution of force displaces material better. 11. Assuming the same mass and initial movement speed, a wider distribution of force displaces material worse. 12. It harder to displace material if you have to displace it faster (ie, it takes more energy to displace the same material in a shorter amount of time, assuming optimal displacement conditions). 13. A wider angle must displace the same amount of material fast because its angle increases at a faster rate. 14. A finer angle must displace the same amount of material slower because it increases angle at a slower rate. So far, let me know what you agree or disagree with. If you disagree, please state why. . What do you mean by resistance and mass? Did you not see him pull out that extremely thick knife with convex? Your theory dictates because it's thicker it shouldn't cut as well, yet the mass behind a convex is not determined by how thick it is. If anything it's even better hence why most people want niku on there blades.
|
|