Info Favorites Register Log in
myArmoury.com Discussion Forums

Forum index Memberlist Usergroups Spotlight Topics Search
Forum Index > Off-topic Talk > The effect of a cross-section on cutting. Reply to topic
This is a standard topic Go to page 1, 2  Next 
Author Message
Eric G.




Location: Arizona
Joined: 08 Feb 2011
Likes: 3 pages
Reading list: 5 books

Posts: 249

PostPosted: Mon 23 Jan, 2012 11:13 am    Post subject: The effect of a cross-section on cutting.         Reply with quote

Hello friends,

I have a question that I think could turn into an interesting discussion here. I have been thinking about this for a while. To begin, my premise is that the distinction that makes a blade a good cutter or good thruster depends largely on its cross-section. For the sake of simplicity, let’s limit this to double-edged straight blades only, no katanas, flachions, falcatas, yataghans etc. I know that there are other factors to consider (many many factors, I’m sure) but I think that I am correct in saying that the cross-section is the number 1 factor when determining the cut and thrust capabilities of the sword. Is that correct? So what cross section makes the most effective cutter and why? When I first thought of this I listed the first ones that came to mind in order from best to worst. My list looked like this:

1) lenticular
2) flattened diamond
3) hollow ground

But then I realized that I left out the hexagonal cross-section. At first I didn’t know where to put these, but then I remembered that most atrims (which are renowned for their cutting awesomeness) are hexagonal in cross section. Again, I know that there is more to it than cross section, but under my premise that the cross section is the factor that gives the most weight to the cutting ability of the blade I could re-do my list like this:

1) hexagonal
2) lenticular
3) flattened diamond
4) hollow ground

Feel free to make your own list to correct mine. I know that many of you have much more experience than I do.

So my main question is this: why? Why do these different cross sections make such a difference? I would be interested to hear your thoughts on how the blade interacts with the target from the moment that it makes contact until it ceases to make contact, and how the cross section makes that seemingly critical difference.

Thanks all.

Eric Gregersen
www.EricGregersen.com
Knowledge applied is power.
View user's profile Send private message Visit poster's website
Nathan Robinson
myArmoury Admin


myArmoury Admin

PostPosted: Mon 23 Jan, 2012 11:18 am    Post subject:         Reply with quote

Cutting what? What are you cutting? What's the medium? Swords are designed for different purposes and part of this is the medium against which they're intended to cut.
.:. Visit my Collection Gallery :: View my Reading List :: View my Wish List :: See Pages I Like :: Find me on Facebook .:.
View user's profile Send private message Send e-mail Visit poster's website
Luka Borscak




Location: Croatia
Joined: 11 Jun 2007
Likes: 7 pages

Posts: 2,237

PostPosted: Mon 23 Jan, 2012 12:31 pm    Post subject:         Reply with quote

There is much more to this. Lenticular slides through target easier, but hexagonal and diamond are stiffer and stiffness is underestimated factor in cutting potential... Ideal blade for cutting would be thin, lenticular and very stiff, but that is unfortunately not really possible so we have to do with trade offs. So good cutting is either achieved with as thin as possible but still stiff enough hexagonal or diamond section or with thin and lenticular but flexible blade. And that all is without including in the mass distribution, mass itself, point of balance, percussion point and so on...
View user's profile Send private message
Bartek Strojek




Location: Poland
Joined: 05 Aug 2008
Likes: 23 pages

Posts: 450

PostPosted: Mon 23 Jan, 2012 12:44 pm    Post subject:         Reply with quote

Luka Borscak wrote:
There is much more to this. Lenticular slides through target easier, but hexagonal and diamond are stiffer and stiffness is underestimated factor in cutting potential... Ideal blade for cutting would be thin, lenticular and very stiff, but that is unfortunately not really possible so we have to do with trade offs. So good cutting is either achieved with as thin as possible but still stiff enough hexagonal or diamond section or with thin and lenticular but flexible blade. And that all is without including in the mass distribution, mass itself, point of balance, percussion point and so on...


Pretty much.

Thin, flat hollow ground blade, even with midrib and what not, will be still better at cutting stuff than stout, thick hexagon seen is some XVII - heavy thrusting swords, generally.

So 'rating' swords according to cross sections defined like that can get tricky indeed.
View user's profile Send private message
Timo Nieminen




Location: Brisbane, Australia
Joined: 08 May 2009
Likes: 1 page
Reading list: 1 book

Posts: 1,494

PostPosted: Mon 23 Jan, 2012 1:01 pm    Post subject:         Reply with quote

The question of "why is the katana the best sword, ever" has generated many replies to the question of what is the best cross-section for cutting. Apart from the obvious points like "thin is good", the katana-question tends to focus on the practical value of the ridge-line.

The question focusses on the cutting of flesh or similar tissue, and substitutes used in cutting exercises. In this case, viscous drag is a major loss of energy as you cut through the target. How to minimise drag?

Thin is good, because you need to displace less material sideways. But narrow (i.e., the front-to-back width of the blade) is good too, since this also reduces drag (witness Turkish and Korean use of short arrows - shorter than the draw length - for long range). So, the best profile would be a narrow, thin razor blade. But with the limits of steel, this is too floppy and weak. So you need enough thickness and width for strength.

Tissue and substitute cutting media are not liquid, despite being wet. Supposedly, the ridgeline allows the blade, past the ridgeline, to avoid contact with the cutting medium, and thus reduce drag. Ridgeline too close to the edge will meant that the edge angle will be large, so the blade won't be sharp enough. So, the compromise is to have the ridgeline back far enough to have an acute enough edge angle for good sharpness, but no further.

Anyway, that is the standard wisdom, aimed at justifying the superiority of the katana. Seems like the kind of thing that might be testable, with a high speed camera, or perhaps computationally.

Applying these ideas to a straight double-edged blade, hexagonal section looks best, out of non-fullered blades. Lenticular with a shallow broad fuller should be good, too, maybe better.

A convex edge ("niku" on the katana) might help, but this is usually explained as strengthening the edge. But consider the convex nose of the tuna, an excellently low-drag fish. (For cutting through liquids, the tuna-section blade would be ideal.)

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
View user's profile Send private message Visit poster's website
Eric G.




Location: Arizona
Joined: 08 Feb 2011
Likes: 3 pages
Reading list: 5 books

Posts: 249

PostPosted: Mon 23 Jan, 2012 3:13 pm    Post subject:         Reply with quote

Nathan Robinson wrote:
Cutting what? What are you cutting? What's the medium? Swords are designed for different purposes and part of this is the medium against which they're intended to cut.


Will some cross sections cut better with some mediums while other cross sections do not? If it really truly makes a large difference in terms of answering the question, I would be interested to hear some thoughts on why as well as what works best where.

If the question needs a cutting medium as a standard then perhaps we can compare milk jugs, tatami mats, and mail? That way it includes price ranges from lowest to pretty darn high? If there are better ones to consider then you tell me.

Luka Borscak wrote:
There is much more to this. Lenticular slides through target easier, but hexagonal and diamond are stiffer and stiffness is underestimated factor in cutting potential... Ideal blade for cutting would be thin, lenticular and very stiff, but that is unfortunately not really possible so we have to do with trade offs. So good cutting is either achieved with as thin as possible but still stiff enough hexagonal or diamond section or with thin and lenticular but flexible blade. And that all is without including in the mass distribution, mass itself, point of balance, percussion point and so on...


How do these trade offs work? For example, say we have swords of equal length, all with different cross sections. Measuring halfway down the blade, will one cross-section be slightly thinner/thicker than another? How would a flattened-diamond and a hollow ground blade compare, for example? Or is it perhaps the angle at which the blade slopes up from edge to center what makes the difference?

Eric Gregersen
www.EricGregersen.com
Knowledge applied is power.
View user's profile Send private message Visit poster's website
J.D. Crawford




Location: Toronto
Joined: 25 Dec 2006

Spotlight topics: 1
Posts: 1,616

PostPosted: Mon 23 Jan, 2012 3:23 pm    Post subject:         Reply with quote

Timo Nieminen wrote:
Thin is good, because you need to displace less material sideways. But narrow (i.e., the front-to-back width of the blade) is good too, since this also reduces drag (witness Turkish and Korean use of short arrows - shorter than the draw length - for long range). So, the best profile would be a narrow, thin razor blade. But with the limits of steel, this is too floppy and weak. So you need enough thickness and width for strength.


I believe there's anothe reason why wide lenticular blades are preferred in swords specialized for heavy cutting (as opposed to slicing). This profile optimizes the amount of mass relative to resistance. This means more energy to shock or penetrate tough surfaces and more momentum to carry through. I think this trumps the small amount of drag added with width. Up to a certain point: in human hands, too much mass means reduced velocity, which (by the formulas 1/2 MV*V and MV) are going to reduce the energy and momentum, respectively. This goes beyond blade profile, but all these factors interact in real world situations.
View user's profile Send private message Visit poster's website
Vincent Le Chevalier




Location: Paris, France
Joined: 07 Dec 2005
Reading list: 15 books

Spotlight topics: 1
Posts: 843

PostPosted: Mon 23 Jan, 2012 3:42 pm    Post subject:         Reply with quote

The two basic variables that I'm aware of are edge angle (a more acute angle will be sharper, more efficient in slices, but more fragile) and blade thickness (the thicker the blade, the more energy will be needed to move it through). These two have direct local effects on the cutting behaviour. The influence of drag according to the shape is of second order in my opinion, possibly negligible compared to the angle at which the blade hits, which creates a "guillotine effect"...

Concave faces (hollow grinding, fullers) in my understanding are mostly there to play with stiffness and mass distribution. Of course both have an influence on cutting, but you can't just consider the local cross-section where the blade meets the target; it's the evolution of the dimensions and shape of the whole blade that determine these factors. Not all blades have uniform cross-sections, practically none have constant thickness, so it becomes complicated real fast Happy

Regards,

--
Vincent
Ensis Sub Caelo
View user's profile Send private message Visit poster's website
Timo Nieminen




Location: Brisbane, Australia
Joined: 08 May 2009
Likes: 1 page
Reading list: 1 book

Posts: 1,494

PostPosted: Mon 23 Jan, 2012 5:36 pm    Post subject:         Reply with quote

J.D. Crawford wrote:

I believe there's anothe reason why wide lenticular blades are preferred in swords specialized for heavy cutting (as opposed to slicing). This profile optimizes the amount of mass relative to resistance.


Vincent Le Chevalier wrote:
The two basic variables that I'm aware of are edge angle (a more acute angle will be sharper, more efficient in slices, but more fragile) and blade thickness (the thicker the blade, the more energy will be needed to move it through). These two have direct local effects on the cutting behaviour. The influence of drag according to the shape is of second order in my opinion, possibly negligible compared to the angle at which the blade hits, which creates a "guillotine effect"...


The main things affecting drag will be the maximum thickness, and the width. If you want a certain mass (per unit length), then a hexagonal section with convex edges puts this in the minimum thickness and width that still gives you sharp cutting edges. So halfway between lenticular and hexagonal. But the difference between this, flat hexagonal, and lenticular would be pretty tiny. Lenticular will be, for a given mass and width, a little thicker, which will make it stiffer.

The story about the ridgeline reducing drag is very much a pro-katana story, and I don't know how much real basis it has. Apart from this as a possible effect, I don't think the details of the cross-section would have much effect, just the width and thickness. The minimum stiffness needed tells you the minimum thickness, the mass (and cross-section) then tells you the width.

The specialised mat-cutting katana tend to have thin wide blades, and flat from the ridge to the edge (no "niku"), basically katana on their way to becoming falchions.

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
View user's profile Send private message Visit poster's website
Michael Edelson




Location: New York
Joined: 14 Sep 2005

Spotlight topics: 2
Posts: 1,032

PostPosted: Mon 23 Jan, 2012 9:01 pm    Post subject:         Reply with quote

.
.
<----does this avatar make me look fat? How about cocky and obnoxioius? I think so.


Anywho...

I don't think cross section is the end all and be all. Mass behind the cutting edge plays a big role (though some might consider that the same thing). Cross section is tricky. As others may have said (I am far too lazy to read the entire thread), thin is good, but stiff is better, thin and stiff is best.

e.g.:
XVa are stiff but lack mass behind the cutting edge and are thick
XIIa and XIIIa are thin and have mass but flex too much which robs energy

An ideal super duper sword would have a good deal of mass behind the cutting edge, be stiff as a board, be thin enough to easily pass through the target and have a nice sharp edge.

New York Historical Fencing Association
www.newyorklongsword.com

Byakkokan Dojo
http://newyorkbattodo.com/
View user's profile Send private message Visit poster's website
Nat Lamb




Location: Melbourne, Australia
Joined: 15 Jan 2009
Likes: 1 page

Posts: 385

PostPosted: Mon 23 Jan, 2012 11:54 pm    Post subject:         Reply with quote

Blade Harmonics” are another (very important) thing to consider, and they are going to be very dependent on cross section ( and related to, but not the same thing as stiffness). I don’t have all that much cutting experience, but it doesn’t take much experience to have encountered a cut against a slightly less forgiving medium where the edge alignment was good, swing “felt” solid, but you contact with the wrong part of the sword and “boing” you just bat the thing out of the way or get a jarring mis-hit. Where the relative sweat-spots are on a blade will rely on cross section, but in a way that is really hard to calculate without some pretty advanced engineering software. I have a suspicion that even 2 swords of identical weight distribution will behave differently with a hit at point x depending on cross section, and vice versa, that 2 swords with identical cross sections but different weight distribution will function very differently, even striking with comparable points on the blade.
View user's profile Send private message
Aleksei Sosnovski





Joined: 04 Mar 2008

Posts: 313

PostPosted: Tue 24 Jan, 2012 3:09 am    Post subject:         Reply with quote

A lot has been said here about mass, thickness, stiffness and acuity being far more important than blade cross section. But here are my 2 cents.

IMHO lenticular, diamond and hexagonal cross sections are more or less equal in performance if their thickness and edge acuity are comparable. Take a diamond cross section, round the ridge and you get a lenticular cross section. Grind the ridge flat and you get a hexagonal cross section. Choice of these cross sections (in case of cut-oriented swords) seems to depend more on desired width and thickness of the blade rather than anything else. Making a wide thin blade with diamond cross section with well-defined center ridge would be quite difficult so lenticular cross section is the choice. Or, if one wants a less acute but more durable edge, he would go for hexagonal cross section, possibly with somewhat smoothed ridges. However if the blade should be narrow making it lenticular or hexagonal will result in edges less acute than desired, so diamond is the choice. For a blade of average width and thickness any cross section can be chosen depending on whatever looks better.

Now a hollow-ground cross-section is entirely different. The more such blade goes into the cutting medium, the more resistance it faces. Not a good thing. From my personal experience knives with hollow-ground blades cut worse than knives of otherwise comparable geometry but with triangle cross section (and of course some secondary bevel). The reason for hollow-ground blades is to create a very stiff but light (in case of rapiers and smallswords) or wide (in case of a cut-and-thrust swords) blade. So generally hollow-ground sword blades would be thicker than blades with other cross sections. However hollow-ground sword blade would be wider than equally thick blade of other cross section and therefore would cut better. Another purely aesthetical reason for hollow grinding may be to create a wide cutting blade with well-defined central ridge (something very difficult to achieve with diamond cross section as I already stated above).

And about drag. It sure does have some effect. Just try cutting some large piece of meat with a wide chef's knife and then do the same but using a narrow fillet knife. However I don't think it would make much difference unless one tries to cut very thick but soft target which can't be found in a normal human body.
View user's profile Send private message Send e-mail
J.D. Crawford




Location: Toronto
Joined: 25 Dec 2006

Spotlight topics: 1
Posts: 1,616

PostPosted: Tue 24 Jan, 2012 7:59 am    Post subject:         Reply with quote

Aleksei Sosnovski wrote:
And about drag. It sure does have some effect. Just try cutting some large piece of meat with a wide chef's knife and then do the same but using a narrow fillet knife. However I don't think it would make much difference unless one tries to cut very thick but soft target which can't be found in a normal human body.


That's right for a slicing, sawing motion through soft tissue, where its all about the edge and there's a lot of back-and-forth drag.

Now, if you want to chop a piece of meat in half, maybe including some bone, with one swift motion, you want a wide heavy blade with some intertia behind it. That is why a filleting knife and butcher's cleaver have opposite profiles. By analogy, for the same thickness, a narrow sword blade might be good for the draw cut against unprotected flesh, but you want a wide heavy blade to chop through limbs or some types of light armour.
View user's profile Send private message Visit poster's website
Gary Teuscher





Joined: 19 Nov 2008

Spotlight topics: 1
Posts: 704

PostPosted: Tue 24 Jan, 2012 9:03 am    Post subject:         Reply with quote

Quote:
Now, if you want to chop a piece of meat in half, maybe including some bone, with one swift motion, you want a wide heavy blade with some intertia behind it. That is why a filleting knife and butcher's cleaver have opposite profiles. By analogy, for the same thickness, a narrow sword blade might be good for the draw cut against unprotected flesh, but you want a wide heavy blade to chop through limbs or some types of light armour.


I think the key concept here is a weapon that "chops" vs one that "slices", though most are a combination to a point of both. I'd guess more on the "chopping" end would be Falcata's, Yatagan's, Falchions, etc.
View user's profile Send private message
Luka Borscak




Location: Croatia
Joined: 11 Jun 2007
Likes: 7 pages

Posts: 2,237

PostPosted: Tue 24 Jan, 2012 10:46 am    Post subject:         Reply with quote

Eric Gregersen wrote:
Nathan Robinson wrote:
Cutting what? What are you cutting? What's the medium? Swords are designed for different purposes and part of this is the medium against which they're intended to cut.


Will some cross sections cut better with some mediums while other cross sections do not? If it really truly makes a large difference in terms of answering the question, I would be interested to hear some thoughts on why as well as what works best where.

If the question needs a cutting medium as a standard then perhaps we can compare milk jugs, tatami mats, and mail? That way it includes price ranges from lowest to pretty darn high? If there are better ones to consider then you tell me.

Luka Borscak wrote:
There is much more to this. Lenticular slides through target easier, but hexagonal and diamond are stiffer and stiffness is underestimated factor in cutting potential... Ideal blade for cutting would be thin, lenticular and very stiff, but that is unfortunately not really possible so we have to do with trade offs. So good cutting is either achieved with as thin as possible but still stiff enough hexagonal or diamond section or with thin and lenticular but flexible blade. And that all is without including in the mass distribution, mass itself, point of balance, percussion point and so on...


How do these trade offs work? For example, say we have swords of equal length, all with different cross sections. Measuring halfway down the blade, will one cross-section be slightly thinner/thicker than another? How would a flattened-diamond and a hollow ground blade compare, for example? Or is it perhaps the angle at which the blade slopes up from edge to center what makes the difference?


The trade off is that since what would be perfect can't physically be achieved, we have to do with what is possible. Everything said here is well said and these people here are very knowledgeable so you will have a good picture after you read all what will be written here.
View user's profile Send private message
Chad Arnow
myArmoury Team


myArmoury Team

Location: Cincinnati, OH
Joined: 18 Aug 2003
Likes: 21 pages
Reading list: 231 books

Spotlight topics: 15
Posts: 9,137

PostPosted: Tue 24 Jan, 2012 11:15 am    Post subject:         Reply with quote

Michael Edelson wrote:

e.g.:
XVa are stiff but lack mass behind the cutting edge and are thick
XIIa and XIIIa are thin and have mass but flex too much which robs energy


Michael,
These kind of absolute statements can cause confusion because reality isn't nearly so simple. The diamond section on members of the XV family can vary quite widely. Some fit your statement and some definitely don't, including an antique I've handled. Also, are you sure all XIIa and XIIIa "are thin and have mass but flex too much which robs energy?" You'd be on surer ground if you said "some" or even "many," or better yet, "ones I have handled." The only absolute in most of this is that speaking in absolutes is dangerous. Happy

Happy

ChadA

http://chadarnow.com/
View user's profile Send private message Visit poster's website
Michael Edelson




Location: New York
Joined: 14 Sep 2005

Spotlight topics: 2
Posts: 1,032

PostPosted: Tue 24 Jan, 2012 12:59 pm    Post subject:         Reply with quote

Chad Arnow wrote:
Michael Edelson wrote:

e.g.:
XVa are stiff but lack mass behind the cutting edge and are thick
XIIa and XIIIa are thin and have mass but flex too much which robs energy


Michael,
These kind of absolute statements can cause confusion because reality isn't nearly so simple. The diamond section on members of the XV family can vary quite widely. Some fit your statement and some definitely don't, including an antique I've handled. Also, are you sure all XIIa and XIIIa "are thin and have mass but flex too much which robs energy?" You'd be on surer ground if you said "some" or even "many," or better yet, "ones I have handled." The only absolute in most of this is that speaking in absolutes is dangerous. Happy


Since no one should (and rarely does) ever speak in absolutes, we have two choices. One is to accompany everything we say with annoying and tedious qualifiers, the other is to trust that people reading our posts know we're not speaking in absolutes. I understand your concern, and I used to use qualifiers, but then I got tired of them. If I had to qualify eveyrthing I said, I would never post.

But your concern is valid, so consider this my qualifier. Happy

New York Historical Fencing Association
www.newyorklongsword.com

Byakkokan Dojo
http://newyorkbattodo.com/
View user's profile Send private message Visit poster's website
Matthew P. Adams




Location: Cape Cod, MA
Joined: 08 Dec 2008
Likes: 8 pages

Posts: 456

PostPosted: Tue 24 Jan, 2012 1:59 pm    Post subject:         Reply with quote

Michael,
Are you sure you would "never" post? I would think that if you found a topic interesting and or had strong feelings about it, that you might post. You'd be on surer ground if you said "rarely" or even "less likely too," or better yet, "probably would not." The only absolute in most of this is that speaking in absolutes is dangerous.

Chad,
Sorry, I just couldn't resist. You are, of course, "absolutely" correct!

"We do not rise to the level of our expectations. We fall to the level of our training" Archilochus, Greek Soldier, Poet, c. 650 BC
View user's profile Send private message
Chad Arnow
myArmoury Team


myArmoury Team

Location: Cincinnati, OH
Joined: 18 Aug 2003
Likes: 21 pages
Reading list: 231 books

Spotlight topics: 15
Posts: 9,137

PostPosted: Tue 24 Jan, 2012 2:08 pm    Post subject:         Reply with quote

Michael Edelson wrote:

Since no one should (and rarely does) ever speak in absolutes, we have two choices. One is to accompany everything we say with annoying and tedious qualifiers, the other is to trust that people reading our posts know we're not speaking in absolutes. I understand your concern, and I used to use qualifiers, but then I got tired of them. If I had to qualify eveyrthing I said, I would never post.

But your concern is valid, so consider this my qualifier. Happy


Michael,
Despite repeated issues with doing so, there are some people who will take things they see online literally, especially when someone with a lot of experience says them. I've taken to often over-qualifying my posts as I've seen issues when I haven't.

IMHO clarity is always worth the small effort of a couple of clarifying words.

Happy

ChadA

http://chadarnow.com/
View user's profile Send private message Visit poster's website
Nat Lamb




Location: Melbourne, Australia
Joined: 15 Jan 2009
Likes: 1 page

Posts: 385

PostPosted: Tue 24 Jan, 2012 8:29 pm    Post subject:         Reply with quote

with regards to the disagreement (obviously friendly) between Chad and Michael, I would like to weigh in and say you are both right. As someone with a background in philosphy and hermeneutics (though not spelling...) I would say that it is indeed usually worth the extra words to increase precision, but in this particular case Michael said Type XVa are stiff" not "XVa's are stiff", meaning that his statement should most properly be interpreted as discussing the "type" not "examples of the type. This may seem like a very, very small distinction, but because swords are representitives of a type to the extent they match what is "typical" of that type, such a statement can be considered to include they qualifyer as a given. [/b]
View user's profile Send private message


Display posts from previous:   
Forum Index > Off-topic Talk > The effect of a cross-section on cutting.
Page 1 of 2 Reply to topic
Go to page 1, 2  Next All times are GMT - 8 Hours

View previous topic :: View next topic
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum






All contents © Copyright 2003-2018 myArmoury.com — All rights reserved
Discussion forums powered by phpBB © The phpBB Group
Switch to the Basic Low-bandwidth Version of the forum