The angle of dangle

[katana]

With numerous blade shapes, profiles, curvatures, types of steel and the differing forged constructions of weapons we see......are there common blade edge angles ....do they vary even with weapons that have similar profiles ? perhaps due to cultural reasons , blade composition etc.

If anyone has any thoughts on the matter, I think it may create an interesting topic.

Kind Regards David

[mross]

Originally Posted by katana

With numerous blade shapes, profiles, curvatures, types of steel and the differing forged constructions of weapons we see......are there common blade edge angles ....do they vary even with weapons that have similar profiles ? perhaps due to cultural reasons , blade composition etc.

If anyone has any thoughts on the matter, I think it may create an interesting topic.

Kind Regards David

Mostly the cutting edge depends on what the target of the cut is, unprotected flesh, leather armour, chain mail, plate armour, etc. Of course then there is use factor as well, thrusters(rapier, small sword), slashers(samurai sword), and chopper(any of the cleaver type weapon)

[Rich]

Perhaps not relevant to the topic, but I find it interesting that the Japanese swords were made by forging (a type of mechanical damascus), laminated with different types of steels and differentially tempered. In a somwhat similar manner, the Nordic peoples (Norwegian/Swedish) did laminated blades and the Finns differentially temperd their blades. However, I've not seen a Nordic blade with both characteristics; laminated and differentially tempered. Even one Finnish maker (Roselli) produces what he calls UHC (ultra high carbon) knives which many have compared to Wootz steels.

Rich S

[fearn]

There are a bunch of things going on.

--Edge geometry depends on what you're chopping. One of the forumites very kindly reprofiled one of my khukuri knives after I chewed the edge up chopping wood with it. As originally made, the edge was too thing for the amount of force I was putting on it. In general, wider edges work better for harder targets, while narrower edges work well for soft targets.

--Steel depends in part on the source (side note: I thought we had a link about steel types, but I don't see it any more. Anyone have it?). In general, places like Scandinavia and Japan depended effectively on bog iron which they had to forge themselves. This gave them a fairly complex mess of material, and that material included a fair amount of blade-weakening silicon in the metal.

To build a sword out of such a mess, you chop the mess into bits with different properties, from high carbon edge material to low carbon back material, weld these bits together into what will become the blade, then fold it repeatedly, not just to make for a stronger complex joint rather than a single weld, but also to control the size of the silicon crystals. Too big a silicon crystal would seriously weaken the blade.

Also, as with the keris, patterned steel is highly decorative, so this process can be deliberately controlled to produce patterns, as with keris blades.

Obviously, if you have a uniform steel source, especially if it's low silicon steel, you don't need to work the material so much.

As for edge hardening, I suspect that depends again on what you want to do with the blade. The argument here is that harder edges are harder to resharpen, and depending on what you plan to do with your blade, building it to be easily resharpened (as with a Swedish mora knife) might be more desirable than have it get dull slowly, then be a real pain in the ass to resharpen, absent a diamond block (as with some modern steels). Also, it's not clear how much different smiths knew about differential hardening. While I'm not a smith, differential hardening doesn't have to be as complicated as the Japanese make it to be. Khukuri makers do it by hand, with a kettle of cold water, and make nice hard edges on their khukuris.

Curvature is a whole other layer of complexity, and I'll let someone else take a swat at that.

Best,

F

[Paul]

I'm only a new boy, so I hope this is on target.

One area not to overlook is how the quality of available steel will influence the angle of the cutting edge by virtue of how the material handles heat treatment. There are some things that you simply can't do with certain steels, especially the more primitive ones.

For example a modern mass produced machete is really very thin for a blade that takes so much hammer (about 3 mm) but a decent one -like say a Martindale will hold up to years of abuse even from cutting sheet iron or digging and still sharpen up just fine with just a file. It may be cheap and crude but, in its own way, its a darn good tool. This is possible both because the steel has been drawn to a soft spring temper and because (when compared to ancient steel at least) it has very good homogenity. These things prevent the steel from cracking under stress.

Primitive steels are too impure to take that kind of abuse, no matter how soft they are drawn, unless they have a much thicker edge and the edge will need to be set at a less acute angle (as in, for example, a medieval sword).

However take that machete blade, cut it down and try and make a good penknife from it and, no matter if you are a heat treatment god, the knife will never hold a fine edge like the cheap white paper steel penknife you will find in a Japanese boy's pocket. The machete steel does not have enough carbon in it to come up hard and sharp. Even modern steels have their limitations but primitive steels are much more limited.

Cultures with more advanced metal working skills will generally be able to produce a more acute edge for a given job than less advanced cultures (e.g. the 15th century Japanese blades versus the 10th Century european). The difference is only a small one though.

If a blade is not ceremonial, one can be pretty sure that its angles will have been set optimally to allow the thinnest edge that is sensible for the intended target and the capacity of the steel to take the likely impact.

Another factor to take into account is the sharpening tools available. If you are sharpening on rocks you find in rivers and such your technique is going to be a bit different and your edge profiles will be limited. I have seen tribesmen sharpen wrought iron on rocks using a backwards stroke (a bit like you would finish an edge with a smooth steel or a strop). They were at pains to correct my normal stroke. It took me a while to figure out that this backwards stroke is less likely to cause a chip and will fold straight small burs in the soft iron. Such a stroke will however only furnish you with a not very acute sabre grind and you would probably ruin other grinds trying on a rough rock. You would also chip a hard steel blade terribly trying this on a rough rock. Hard steel (even the best) chips relatively easily compared to softer tempers.

Now if you have nice flat hones sourced from a stone with uniform particle sizes, then you can sharpen away happily to very thin edges in very hard steels that would chip if you were to hit an unexpectedly large particle in a hone. This is another reason why the Japanese were able to sharpen such hard edges so well -they had lovely sedimentary stones that could be found with differing but nearly uniform particle sizes.

Hope this is useful.

[katana]

Thank you for all the replies so far , often , it seems that 'definative' edge angles are described for knife sharpening and some for sword edges....but none seem to take into account of the type of steel/iron, edge hardness, blade profile etc. I wondered whether 'typical' and common ethno blades such as Kaskara, khanjar, Saifs, Kris etc had evolved with a 'traditional' optimum angle or that there was a range of several degrees and therefore less important.
It is sometimes very surprising how a few degrees of angle can greatly improve the cutting abillity of a blade. Is there any evidence that there is an ethnic belief in the 'perfect' angle ?

Kind Regards David

[Rich]

It's been my experience with Nordic and many other cultures knives, that the angle of the bevel is determined in large part by the thickness of the blade and the height of the bevel (ridge line). Example: most Norwegian knives are quite thin (as are Swedish knives) - they have low bevels while Finnish knives are thicker and have a higher bevel. Not sure if this applies to swords, but the principle seems reasonable. Most US and European knives seem to go with about a 20 degree angle; I prefer a more acute angle of about 15 degrees.

Rich

[Edster]

Hello David,

Interesting question. Here's my two cents worth.

Kaskara blade smiths I interviewed in Kassala said they made all their blades by eye. No measurements were made. Naturally, over the years each smith establishes a edge profile that "looks good, seems right" to him. After being forged, blades were descaled and smoothed by others. Then the smith cold works the edge to further hardening it and does final smoothing and edge profile setting. The actual sharpening was apparently done by others using a file and or a stone. Over time the blades were resharpened by users, also by eye I imagine. Just like when you and I hand sharpen a blade. We work it until it appears "sharp enough" and don't go for any of the supposedly optimum angles offered by those who sell knife sharpening kits.

No doubt other blade making traditions approach the edge differently.

Regards,
Ed

[Paul]

I think I get what you mean now. Its a good question. I think it would be quite revealing if one were to find a culture that defined "perfect angle". This would suggest that the art of weapon making had become so refined as to be "fossilized" in that culture. -That tradition had made a weapon so prescribed that technological innovation and practicality were no longer as valued as custom. It would be a bit like defining the value of a working dog by its conformation to breed standards, rather than by the quality of its work.

As someone who cuts for a living I know you can only define a perfect angle for a specific tool of a given steel at a given hardness doing a specific job, accepting a certain sharpening interval and a certain risk of chipping. That works for controlled conditions like machine tools in a factory but, with the exception of duels, combat situations are rarely controlled, so a warrior is taking a risk if he adheres rigidly to tradition in all circumstances.

One should also consider that the angle of grind varies along most good blades depending on the job which that section does -be it the point of a scandi knife that is usually blunter because it must cut curves in wood and pierce hard things or the first half of a sword blade that gets used in a fighting style that uses much edge on edge parrying and so risks chipping. A culture would need to be quite prescriptive to have rules for all these things. That would be very interesting. It would be a very stable culture one imagines, more prone to infighting than coming into contact with a range of differently armoured enemies.

However, advanced armies need to specify standards to smiths or they may get substandard items. Here there must be set angles by default of pattern measurements.

For example the Fairbairn -Sykes pattern makes a very good balance of trade offs in edge angle for piercing, cutting and edge strength in a knife of modern carbon steel, designed primarily for stabbing men who are not wearing armour but may be wearing thick winter coats. The knife is a British classic but when the Americans tried the knife, they made it too cheaply (I think it was an example of competetive tender gone wrong). The manufacturer used substandard steel for what is actually quite a delicate blade and the knives were found to break too much, which was one reason the americans rejected the knife. Even a space age superpower cannot place blind trust in a tried and tested pattern for a weapon.

I wonder how far back western military blade patterns go and in what other cultures official blade patterns can be found?

[Timo Nieminen]

Originally Posted by katana

are there common blade edge angles ....do they vary even with weapons that have similar profiles ?

They vary even over the same weapon. Just measured a knife/sword. Flat grind, distal taper, reverse profile taper (i.e, the blade gets thinner and wider towards the tip). Edge angle is 22 degrees where the edge starts near the hilt, and drops down to under 4 degrees near the tip. (There are many small chips near the tip.)

The same effect, though not so extreme, occurs with convex ground weapons/tools with the same kind of taper (or just distal taper, or just reverse profile taper). E.g., various goloks.

Often enough, the blade section itself changes along the blade. Many fighting swords end in very thin (and still wide) tips, usually convex ground, which can have very low edge angles. E.g., the broad-bladed Turkish kilij, some tulwars, parang nabur, lots of European military sabres, oxtail dao, some jian.