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Vincent C




Location: Northern VA
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PostPosted: Sat 31 Jul, 2010 4:18 pm    Post subject: Blade geometry         Reply with quote

I was wondering what some differences were in performance between various sword cross sections.

Specifically, I was wondering what the difference was in cutting/thrusting abilities of the hexagonal cross section when compared to the diamond or lenticular.

Another was question was that of durability, which cross section can take the most punishment?

Also, I realize that hollow grinding a diamond cross section makes it better suited for the thrust, but it seems that this would decrease both its cutting ability and durability, since it makes the edges so much thinner but with a high central ridge.

If someone could help me along or point me in the right direction, that'd be great.

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Toke Krebs Niclasen




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PostPosted: Sat 31 Jul, 2010 4:49 pm    Post subject:         Reply with quote

I am not an expert on this, but will not let that stop me.

The diamond section is stiffer than the lentil, but quite likely harder to make right.

As for hollow grinding, you are not supposed to grind all the way to the edge.
Ideally there is a ridge right behind the edge, giving it the same strength as a non hollow ground blade.
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Vincent C




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PostPosted: Sun 01 Aug, 2010 8:58 pm    Post subject:         Reply with quote

I'm more than aware of the comparisons between diamond and lenticular cross sections, my question states that I'd like to know how hexagonal compares between them.

I'm not sure what you mean when you say you're not supposed to hollow grind to the edge, all the diagrams and actual swords with hollow grinding I've seen have been diamonds with concave sides going all the way out to the edge.

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Toke Krebs Niclasen




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PostPosted: Sun 01 Aug, 2010 11:03 pm    Post subject:         Reply with quote

Quote:
I'm not sure what you mean when you say you're not supposed to hollow grind to the edge, all the diagrams and actual swords with hollow grinding I've seen have been diamonds with concave sides going all the way out to the edge.


That sounds like a mistake.
Ideally the hollow grind leaves the material thickness higher right before you get to the edge.
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Jean Thibodeau




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PostPosted: Mon 02 Aug, 2010 12:20 am    Post subject:         Reply with quote

Toke Krebs Niclasen wrote:
Quote:
I'm not sure what you mean when you say you're not supposed to hollow grind to the edge, all the diagrams and actual swords with hollow grinding I've seen have been diamonds with concave sides going all the way out to the edge.


That sounds like a mistake.
Ideally the hollow grind leaves the material thickness higher right before you get to the edge.


I agree that type of hollow grind might be good for a strait razor for maximum cutting ability but it would also be a fragile and easily damaged edge that would notch deeply.

One way to look at the geometry of a hollow ground blade is to view it as like a very wide fuller on each side of a thick spine that ends before the edge that can be a secondary bevel or an apple seed kind of bevel.

The very thinnest part of the blade is close to the edge but thickens just very slightly before the start of the secondary bevel which forms the actual cutting edge to strengthen it.

Alternatively one could have a hollow grind that finishes with parallel planes that would leave a flat of reasonable thickness before again curving down into a secondary bevel or an apple seed edge.

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Vincent C




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PostPosted: Mon 02 Aug, 2010 11:06 am    Post subject:         Reply with quote

Oh, I see it now.

I never noticed that on the earl before, it's practically in my face now.

So a lot of the swords (like some type XXI and some la tene swords) that look like they have really wide double-fullers are actually hollow-ground?

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Peter Johnsson
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PostPosted: Mon 02 Aug, 2010 11:27 am    Post subject:         Reply with quote

Vincent C wrote:
Oh, I see it now.

I never noticed that on the earl before, it's practically in my face now.

So a lot of the swords (like some type XXI and some la tene swords) that look like they have really wide double-fullers are actually hollow-ground?


The classic hollow ground section is like a diamond cross section with almost all of the flats removed by grinding on the radius of a wheel. Enough material is saved in the edge so that it can have much the same apple seed form as a lenticular sectioned blade. How neat or thin the edge is depend on the sword. Heavier blades will tend to have thicker edges while light and slim blades can have only the smallest little apple seed edge shaped after the main hollow bevel. Sometimes the transition to the apple seed edge can indeed form a slight rise, but most often it is an invisible transition without this ridge. Visually there may seem to be a ridge, but this is a matter of honing and polishing, more than an actual ridge behind the very edge.

On those La Tène blades with wide double fullers it is not really a classic hollow ground section. They ridges behind the edge are too thick and there is not enough difference in thickness to the spine of the blade to really compare. In a wide sense we may say they have some elements in common, but they should be recognized as two different types of cross section, or e will begin to confuse matters.

Same goes with the XXI blades: the double (or triple) fullers can be seen as formed in very wide and thin lenticular sections, but there is too much difference: they have dedicated edge bevels and very different geometry in the point. But if we want to stretch it we can note some basic similarities in how the blades are constructed: a simple basic cross section that is elevated by clever use of hollows and fullers.

To return to your original question:
you can make most cross sections perform in certain ways. They tend to lend themselves most naturally for certain applications but there is a wide overlap. You cannot expect one type to always be better than an other type, simply because of their inherent principal differences.
There are many reasons why you would choose one type of section before another. It does not only have to do with function. It is also a matter of manufacturing methods, material characteristics (quality of the steel and its hardenability) as well as fashion and not to forget: Economy.
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Jean Thibodeau




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PostPosted: Mon 02 Aug, 2010 7:33 pm    Post subject:         Reply with quote

Thanks Peter for explaining it more clearly and with more " nuances ": I compared it to wide and shallow fullers as an example of a type of hollow grind and to get away from the extreme of the hollow grinds that meet in a thin edge without a secondary bevel. Some blades may have a subtlety thickening before the secondary bevel and other are just ground to the same thickness near the secondary bevel that an elliptical grinded blade would have before it's secondary bevel.

A blade meant for heavy duty work against armour, or just to handle edge parrying with less damage, will have thicker edges than a sword or knife meant for very fine slicing cuts.

Anyway, just repeating what Peter said. Wink Big Grin Cool

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Michele Hansen




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PostPosted: Mon 02 Aug, 2010 10:55 pm    Post subject: Re: Blade geometry         Reply with quote

Vincent C wrote:
I was wondering what some differences were in performance between various sword cross sections.

Specifically, I was wondering what the difference was in cutting/thrusting abilities of the hexagonal cross section when compared to the diamond or lenticular.

Another was question was that of durability, which cross section can take the most punishment?

Also, I realize that hollow grinding a diamond cross section makes it better suited for the thrust, but it seems that this would decrease both its cutting ability and durability, since it makes the edges so much thinner but with a high central ridge.

If someone could help me along or point me in the right direction, that'd be great.


I'm a total newbie when it comes to blade styles, but here is something I learned from the weapon master at Camlann Medieval Village, a re-enactment organization depicting daily life in 1376 England.

The diamond (lenticular?) shaped blade has a "poinard" shape, widely used in the 14th C. to thrust into the neck, armpit, or other vulnerable areas not protected by plate. A long sword, no matter how sharp, cannot cut through well-made plate harness over a quilted gambeson, but it can strike with great force and suffer no damage. These "diamond" profile blades weigh around 3 lbs. and are wonderfully flexible. Those heavier, flatter,sharp edged blades of earlier eras were used to break, and shread the links in mail. The long swords I see in use at Camlann are about 2" in width at the base, and angle straight to a point at the tip.

As far as which is a better blade? The pros above are better suited to answer that, but I think it really depends on how strict you are in maintaining historical accuracy.

Il est apelée de Montfort. Il est el Mond, et si est fort. Si ad grant chevalrie; Je vois et je m’ acort. Il eime le droit, et het le tort. Si avera le mestrie!


Last edited by Michele Hansen on Mon 02 Aug, 2010 11:27 pm; edited 4 times in total
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Nathan Robinson
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PostPosted: Mon 02 Aug, 2010 10:59 pm    Post subject: Re: Blade geometry         Reply with quote

Michele Hansen wrote:
The diamond (lenticular?) shaped blade has a "poinard" shape, widely ...


Lenticular blade shapes are not diamond, they are "lozenge-shaped" (no mid-ridge as in a diamond section or flat central area as in a hex section).


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Michele Hansen




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PostPosted: Mon 02 Aug, 2010 11:34 pm    Post subject: Re: Blade geometry         Reply with quote

Nathan Robinson wrote:
Michele Hansen wrote:
The diamond (lenticular?) shaped blade has a "poinard" shape, widely ...


Lenticular blade shapes are not diamond, they are "lozenge-shaped" (no mid-ridge as in a diamond section or flat central area as in a hex section).


Wow! These images are fantastic, and are really helpful. I know the swords at Camlann are narrow fullered, but are ground into a diamond shape nearer the tip. I think the purpose of the diamond cut is to add strength to the blade tip when it is used for a thrust rather than a cutting attack. Besides, that fullered region is flatter. It makes sense. That diamond ridge would probably get nicked during a parry, like an edge. Thanks so much for helping me understand the terminology concerning sword profiles, and blade characteristics. I have edited the end of my first post to make it less confusing, but I left my initial error. I'm a student of sword-making, not a craftsman. I appreciate your quick reply. Nice to meet you online!

(edited to correct the Camlann blade shapes on August 11, 2010)

Il est apelée de Montfort. Il est el Mond, et si est fort. Si ad grant chevalrie; Je vois et je m’ acort. Il eime le droit, et het le tort. Si avera le mestrie!


Last edited by Michele Hansen on Wed 11 Aug, 2010 2:02 pm; edited 2 times in total
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Vincent C




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PostPosted: Mon 02 Aug, 2010 11:48 pm    Post subject:         Reply with quote

But what about inherent characteristics of hexagonal cross sections?

I've read a lot about how, in general, lenticular cross sections are better for cutting due to flexibility whereas diamond cross sections are supposed to be better for thrusting due to their relative rigidity, and a hollow ground blade being good for "cut and thrust" types of swords due to both rigidity and a nasty edge.

But I haven't found anything discussing the general characteristics of hexagonal cross sections.
I assume that having the center of the blade flattened may lend itself to a more cut-oriented type of cut-and-thrust type of sword.

But that's an assumption, I also had thought hollow grinding was done all the way to the edge.

I'd understand if it was done for display purposes, The National Native American museum in DC has a type XIX bastard sword on display, and it's quite stunning to look at.

Also, thank you all for the insight (especially into hollow-grinding), it's helped clear a few things up.

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Nathan Robinson
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PostPosted: Mon 02 Aug, 2010 11:56 pm    Post subject: Re: Blade geometry         Reply with quote

Michele Hansen wrote:
Wow! These images are fantastic, and are really helpful.


Read our featured articles. That image is from our Understanding Blade Properties article.

Nice to meet you, too! Welcome to the site.

Cheers

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Vincent C




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PostPosted: Thu 05 Aug, 2010 1:13 pm    Post subject:         Reply with quote

The understanding blade properties article is good, but it still for the most part ignores hexagonal cross-sections.

What was their use? was it purely ornamental or did they actually have a legitimate application.

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Jean Thibodeau




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PostPosted: Fri 06 Aug, 2010 1:33 am    Post subject:         Reply with quote

Vincent C wrote:
The understanding blade properties article is good, but it still for the most part ignores hexagonal cross-sections.

What was their use? was it purely ornamental or did they actually have a legitimate application.


Everthing else being equal the hexagonal cross section is going to have a bit more mass and stiffness for a blade of the same profile taper and similar distal taper with a diamond section: I know that my Doge has a lot of blade presence for a medium width blade at 1.5 " wide that one would expect from a wider 2" wide bladed sword and it's not whippy or droopy.

Aesthetic are always also a factor in all sword designs to some degree. ( Anyway, that is my best guess. Wink ).

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Peter Johnsson
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PostPosted: Fri 06 Aug, 2010 7:35 am    Post subject:         Reply with quote

Comparing three blades with same width and thickness, one being lenticular, one diamond and the third hexagonal, the hexagonal will be stiffest, but also heaviest.

Diamond shaped blades can be made very stiff without adding as much mass as a hexagonal blade would get with same thickness.

With the alternative being a lenticular blade, you will get a slightly heavier but also quite stiffer blade if you give it a hexagonal section given the same width and thickness.
You can make a hexagonal sectioned blade thinner than a lenticular blade and still have same degree of stiffness.
For very thin and light blades, a hexagonal section is a way to provide some sturdiness to an otherwise too flexible a blade.

There are also reasons in manufacture why a hexagonal section is a good idea. This has to do with how blanks were forged and blades ground. As with most things concerning swords there are more than one reason why they were made the way they were.
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Vincent C




Location: Northern VA
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PostPosted: Fri 06 Aug, 2010 8:02 pm    Post subject:         Reply with quote

Quote:
Everything else being equal the hexagonal cross section is going to have a bit more mass and stiffness for a blade of the same profile taper and similar distal taper with a diamond section: I know that my Doge has a lot of blade presence for a medium width blade at 1.5 " wide that one would expect from a wider 2" wide bladed sword and it's not whippy or droopy.


Quote:
With the alternative being a lenticular blade, you will get a slightly heavier but also quite stiffer blade if you give it a hexagonal section given the same width and thickness.
You can make a hexagonal sectioned blade thinner than a lenticular blade and still have same degree of stiffness.
For very thin and light blades, a hexagonal section is a way to provide some sturdiness to an otherwise too flexible a blade.


Thanks guys! That question had really been burning me up, I appreciate it.

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Kel Rekuta




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PostPosted: Fri 06 Aug, 2010 8:36 pm    Post subject:         Reply with quote

Vincent C wrote:
The understanding blade properties article is good, but it still for the most part ignores hexagonal cross-sections.

What was their use? was it purely ornamental or did they actually have a legitimate application.


A heavy sword for combat against highly developed plate armour. Mostly used as a short spear and frankly, a pry bar. Still capable of devastating cuts against more lightly armoured opponents. Most rebated swords we at AEMMA use in harness have hexagonal cross sections. Unfortunately most crappy crowbar ornamental SLOs do as well. The difference is in the resilience of the blade, the flex if you will.
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