Ethnographic Arms & Armour - View Single Post

Paul · 11th May 2012, 08:45 PM

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.

11th May 2012, 08:45 PM	#5
Paul Member Join Date: Oct 2011 Posts: 5	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.