Cutting Planes of blades

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Cutting Planes of blades

Post by Chris Fields » Fri Aug 24, 2007 11:26 am

I was just curious, do Chinese swordsman cut with different cutting planes of the blade like what is done in Japanese Tameshigiri? I know chinese swords normally have less of a cross sectional taper than japanese swords, but I would think it would still come into account. Check the picture I have below:

Image

The picture describes how the blade passes through the target for the most part doing Tameshigiri. Blade doesn't actually cut through the air strait like most people think, but at an angle where one flat of the blade is lined up perpendicular to the cutting plane. Th arrow in each picture is the cutting plane and direction of the blade travel.

Just curious. Thanks
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Post by PaulC » Tue Aug 28, 2007 2:55 pm

I'm not sure that Katana or any other type of blade actually cuts more efficiently presenting the blade to the target in this manner.

Upon impact this method would twist the sword in the hand(s) and present a much larger surface area to the target causing a huge amount of material to compress ahead of the cut.

Perhaps you are thinking of the optimum angle you want to cut a target at?

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Post by Chris Fields » Tue Aug 28, 2007 3:10 pm

This technique is used in Tameshigiri to control where the sections that are being cut will travel. Blade twist does happend if you angle it a bit too much, however, if you get that angle correct, the blade cutts more like a chisel than a razor.

This may be a modern developement used in only Tameshigiri though. People who are good, can use different angles of cuts change what piece of the cutting mat they want to move. For instance, if you want to make the top fly off and keep the base still, you angle your blade so that is pushes the top piece away. On the other hand, if you want the top piece to remain where it is, say, to perform another cut to it before it falls, then you angle the blade to push the base away from the cut.

People who are really good at this, can place the cut sections where ever they want them at any angle. It is really neat to watch in person.

The more I think about it though, I don't think it is just a modern tameshigiri developement. The way Japanese swordsman slice at downward angles, keeping the left hand centered on the body right in front of the abdomin, The blade is forced to follow these "chisel" angles, and not cut in a strait line.
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Post by Scott M. Rodell » Wed Aug 29, 2007 6:47 am

Chris Fields wrote:This technique is used in Tameshigiri to control where the sections that are being cut will travel... This may be a modern developement used in only Tameshigiri though...
I suspect that is exactly what it is. I mean no offense to our friends who practice Japanese swordsmanship, but this sounds more like a pallor trick than swordsmanship. Cutting hard targets in the manner suggested will result in the blade bouncing off the target. I can not tell you the number of times I have observed a new student's cut bounce right off even green bamboo, that is only 1 1/2" in diameter, due to a blade alignment like you are suggesting.

I also suspect that those preforming this trick are cutting single or half mats. About the worse thing than could have happened when cutting in combat would have been getting one's blade bound in the target. Angling the blade in the manner suggested increases the friction between the target & the blade. This, in turn, would increase the likelihood that the blade would bind.

I believe it is important that we distinguish Test Cutting (shizhan) that is designed to improve our understanding of historical swordsmanship & test cutting that is a practice in & of itself. There is a great deal of test cutting that, while it involves very real skill, has little to nothing to do with how one would cut in combat. Understanding the difference between these types of cutting is not a matter of "good" cutting vs. "bad" cutting, but of clarity of purpose.

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Post by Scott M. Rodell » Wed Aug 29, 2007 6:56 am

Scott M. Rodell wrote:... it is important that we distinguish Test Cutting... designed to improve our understanding of historical swordsmanship & test cutting that is a practice in & of itself. There is a great deal of test cutting that, while it involves very real skill, has little to nothing to do with how one would cut in combat...
Here is an example of what I was writing about:
Angel Sword Tatami Mat Cutting Competition at TRF 2004
http://video.google.com/videoplay?docid ... &plindex=1

The men cutting in this video have a very real skill, however they are not using historically accurate arms, nor would one ever cut an opponent on the battlefield who was only 6" thick, but 4 or 5' wide... Personally, I don't find such practice of interest, as it would do little to improve my understanding of jianfa, but to each his own...

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Post by Chris Fields » Wed Aug 29, 2007 10:02 am

Again, i emphasize the last comment I made:

"The more I think about it though, I don't think it is just a modern tameshigiri developement. The way Japanese swordsman slice at downward angles, keeping the left hand centered on the body right in front of the abdomin, The blade is forced to follow these "chisel" angles, and not cut in a strait line."

The friction during the cut actually increase only the one side, but decreases on the other almost down to zero. I could run through the numbers, but my guess is that the friction problably come out close to the same. Again, if the cut is slightly over angled, then it will bounce or twist in your hand. However, according to traditional Japanese technique, especially in downward angle cuts, the blade has to be slightly angled, and the sword cuts like a chisel, not a razor.
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Post by Scott M. Rodell » Wed Aug 29, 2007 10:46 am

Chris Fields wrote:... if the cut is slightly over angled, then it will bounce or twist in your hand... according to traditional Japanese technique, especially in downward angle cuts, the blade has to be slightly angled, and the sword cuts like a chisel, not a razor.
Is there a specific lineage this is from?

Have you observed anyone cutting hard tagets with this method? Thick or dry bamboo? Are you speaking of two-handed cuts or both two-handed & single handed cutting techniques?

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Post by Chris Fields » Wed Aug 29, 2007 4:51 pm

I'll check on the lineage.

These are both two handed cuts and single hand cuts from the draw. I have not seen bamboo cuts in person, only mats. They do thick bamboo as well, though I have not seen it in person yet. There in the middle of growing a nice bamboo garden, don't know when they'll have pieces ready. I don't know if they cut dry bamboo, I will ask next wednesday.
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Post by nick_nameless » Thu Aug 30, 2007 3:55 pm

From an engineering, physics POV, what you are suggesting doesn't really make sense.

Essentially the technique you are suggesting using creates a situation where the horizontal COG of the blade (that is the center of mass between the edges of the blade, a plane that travels the length of the blade) will travel parrallel to the point of impact, but not in line with it. When the blade impacts a surface, this creates a "moment" within the structure, or essentially a twisting. That is what causes a blade to bounce as Mr. Rodell suggests.

As a counter point to this, impact mechanics are significantly more difficult to predict than most physics issues. There may be some factor that comes into play, and perhaps the situation you are describing here is part of the thought process behind the design of modern "tanto style" knives such as the Timberline Specwar that was produced about 10 or so years ago. I believe there are knives of this design currently made by Benchmark as well.

A sword is essentially a big knife, but because of the length versus width versus material strength issues they can perform very differently when subject to different kinds of loads. Just as an example, a sword receiving a load along it's length, say by the tip being pressed agains concrete and pressure being applied to the pommell, would have a very good chance of buckling and subsequently bending. A knife would have to be subject to a tremendously larger force to potentially buckle.

It's an interesting discussion, to say the least.

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Post by nick_nameless » Thu Aug 30, 2007 3:58 pm

Here is an article Graham Cave posted in one of the other forums here. Perhaps it will shed some light.

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Post by Chris Fields » Tue Sep 04, 2007 11:05 am

I am an engineer, so I know what you are saying. I said and thought the same things until I saw the person cutting in person.

But think about it, it does make sense. If done at the correct angle, the blade does not twist because it is passing along one of its planes like a chisel.
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Post by nick_nameless » Tue Sep 04, 2007 2:07 pm

Chris Fields wrote:I am an engineer, so I know what you are saying. I said and thought the same things until I saw the person cutting in person.

But think about it, it does make sense. If done at the correct angle, the blade does not twist because it is passing along one of its planes like a chisel.
I am not necessarily disagreeing...merely presenting some discussion on mechanics. As I mentioned, there are knives that have offcenter cutting points and so that in and of itself is a bit of an anomally in the discussion.

I would be interested to see any kind of theory/dynamic model that might provide insight as to this.

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Post by Chris Fields » Tue Sep 04, 2007 3:14 pm

Oh I understand :D

I wish I had slow motion video of some mat cuts.
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Post by Chris Fields » Thu Sep 20, 2007 2:50 pm

I believe this is the web page for the Tameshigiri group in St. Petersburg Fl. Hope this is insightful.

http://www.toyamaryu.org/edge_geometry.htm
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Post by Scott M. Rodell » Fri Sep 21, 2007 8:29 am

Dear Chris,

Thanks for posting that link.

Unfortunately, not all the videos are working at this time. I watched those that were repeatedly, both at full speed & freeze frame. To be honest, I do not see a "chisel" angle being used. In fact, quite the opposite, the edge angle & the plane of the cut are parallel. I was not trained in any school of Japanese swordsmanship, so I did not want to rush to comment on this thread & the chisel angle proposed in the first post. But since this post I've spoken with other experts test cutters, including those trained in Obata's school. None of the Japanese school trained cutters I spoke with use a chisel angle. These practitioners all confirm what my experince & training shows, the plane of the cut & the edge angle should be parallel. Indeed, if these 2 angles are not parallel, what happens when you contact a hard target is that the blade skips off the surface without cutting. This can occur even when the target is even green bamboo as thin as 1 1/2" (3.8 cm.).

When a blade is actually cutting thru a target, if the edge is properly shaped, the material being cut is push away from the blade. In some cases, when the cut is fast enough, you can actually see the top piece pop straight up & come straight back down & balance for a moment on the bottom piece.* If a chisel angle was being used, the top piece would be pushed to one side & would fall directly over.

By pushing the material being cut thru away from the blade, friction on the blade is reduced. If one cut into a soft target with a chisel angle, one blade flat would be pushed into the target material causing greater friction, thus slowing the blade.

In short, I'm afraid the labeling in your diagram in the first post is backwards...

*You can see as example of this is the video:
Shan Cut with a Chinese Saber
http://video.google.com/videoplay?docid ... &plindex=0

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