Steel chisels cutting wood and bone

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Summary
Hardness and structures of bone, wood and steel have interesting effects. Any observations are welcome.
Below 17 degrees bevel , a steel chisel cuts pine wood without tearing shreds but 25 degrees is the upper limit for hardwood. Bone is said to resemble wet pine-wood.

2mm thickness is the limit for steel cutting bone.

.". difficulties arise for the surgeon when using conventional chisels, due to the large chisel cross-section, namely in particular the risk of a premature and, in some cases, uncontrollable fracturing of the bone, excessive traumatism of the bone.. Since, by virtue of the guide, the chisel blade can be very thin, eg. 0.5 or 1.0 or 1.5 or 2 mm, there is only a small widening of the cutting gap by the chisel thickness. The risk of premature fracturing and jamming is thereby decreased. The traumatism of the bone is reduced."
https://patents.justia.com/patent/4586496


https://siamagazin.com/this-man-turns-lignum-vitae-wood-into-an-extremely-sharp-knife/
Measuring the thickness of the blunt side and width ( using his fingers and nails to calibrate the mm. ruler) then the knife has a 20degree bevel . It is 3mm thick at 10mm back from edge. A sword is about 12degrees . It is 2mm thick at 10mm back , as is the patent surgical chisel. Both in angle and thickness the wooden knife is not suited for smooth chisel cutting into bone ( slicing cucumber is fine, no problems, I found). A 25degree chisel cuts hardwood and could be 2mm thick at 10 mm back but 2mm wood-blade is not good. Pine is about 10% steel strength and Lignum hardwood is around 15% steel ( so a .5mm thick chisel is possible).

Tests of sharp hardwood ( Janke 20k N, 1000kg m3) and steel on pine , pig-skull and Synbone forensic skull confirm this . Momentum was at 33mph/53kph by sports radar speed-gun. Wood can't chisel bone.
 
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anorlunda

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You ask no question. What it's your purpose for this thread?

Are you the author of that article? Do you have a personal interest in that patent?
 

Baluncore

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A good read on the subject is “The Science and Engineering of Cutting”, by Tony Atkins. (The Mechanics and Processes of Separating, Scratching and Puncturing Biomaterials, Metals and Non-metals). 2009, Paperback ISBN: 9780750685313.
 
If the data given is valid , then my purpose is to question these:
The death of Kaakutja: a case of peri-mortem weapon trauma in an ...

https://www.cambridge.org/core/product/.../core-reader

Sep 15, 2016 - Experiments by Lewis (2008) using a range of sword types illustrate how ... closely resembles that produced by an African 'Samburu' sword. pp 1327,8

Kaakutja, Perhaps the First Known Boomerang Victim - The New York ...

https://www.nytimes.com/2016/10/18/science/first-boomerang-victim-australia.html

Oct 17, 2016 - The skeletal remains of Kaakutja, an aboriginal man who scientists think was killed by a boomerang about in the 13th century.

NYTimes has an image of the excised bone. Would you agree that wood is unable to give that smooth slice across the laminated cortical plate? Did a sword do that?
 

anorlunda

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OK, that is much more clear. Thank you for your cooperation.

But it also suggests that the forum should be biology, not mechanical engineering. Forensic scientists study medicine to learn about bone fragments. Medical examiners in particular.

I'm going to move the thread to biology.
 

berkeman

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". difficulties arise for the surgeon when using conventional chisels, due to the large chisel cross-section, namely in particular the risk of a premature and, in some cases, uncontrollable fracturing of the bone, excessive traumatism of the bone..
What are some typical orthopedic surgical procedures that use chisels? I've only done a little searching so far, so it does appear that they are used. What are they used for in which specific surgeries? Thanks.

https://www.sklarcorp.com/orthopedic/chisels/hibbs-chisel-8838.html
 
I've used a cleaver in butchery but don't do surgery. Willing to try , low fees.
That chisel is for "heavier bone" but is a massive 12mm , 1/2 inch thick. wow. Braun chisels tell me their chisels are 2mm thick. https://o.aolcdn.com/images/dims3/GLOB/legacy_thumbnail/1200x630/format/jpg/quality/85/http://i.huffpost.com/gen/1135566/images/n-MARK-FRASER-INJURY-SKULL-628x314.jpg

An ice hockey puck is about a boomerang's weight , but probably faster
for Momentum. The trauma here is comminuted depressed fracture but not cutting the inner cortical plate . The length of the cut on a puck-circle shows the depth is about 4mm, 1/6 inch which is halfway through the skull. This is not a slice across the plate like the Kaakutja fracture.
 

Baluncore

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A wooden boomerang that is designed to return is light-weight and has a rounded leading edge and sharp minimum-drag trailing edge like an airfoil. Most people who get a boomerang try first to throw it, spinning backwards.

Do not underestimate an Australian hunting boomerang. It is heavier and has a sharper leading edge at the tip. It is not expected to return. It is designed for range in a straight line, to fly through a flock of birds until it hits one. The wood species is selected to be bent and dense, then it is heated and shaped in a fire to make it harder.

I believe the injury to the skull pictured could have been done by a hunting boomerang. There are several contact geometries to consider. If the initial contact was with the tip of the forward travelling blade, the rotation and linear flight energy combined would be available to cut into the bone. A flake of bone was then broken out. Penetration may have been initially aided by the surface flesh that prevented deflection.

Scratch marks on the bone show it was mainly sharp-edge pressure and not the slicing action expected of a curved slashing blade.
 
There are many web examples of sword cuts by edge pressure.

https://render.fineartamerica.com/images/rendered/medium/canvas-print/mirror/break/images-medium/sword-blade-trauma-1903-science-source-canvas-print.jpg

Thickness is the problem . Blades in Australian Museum Sydney are 5-10mm thick at 10mm back from edge. The profile is bi-convex like bullet nose. Skull is about 8mm thick on frontal sides so the boomerang in Kaakutja skull has to be also in the outer cortical plate , not just within the trabeculae diploe. This gives the ice-hockey puck effect compared to 2mm sword. Bone also hardens under sudden shock ( partly due to liquid in the marrow) causing brittle random fractures.

Here is another angle showing the straight , clean cut.
https://www.google.com.au/search?q=kaakutja+skull&rlz=1C1CHFX_enAU797AU797&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiZzsjfzefhAhWzgUsFHW1nDkwQ_AUIDigB&biw=1024&bih=625#imgrc=uRsNLy3v0UdJnM:
 

Baluncore

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This gives the ice-hockey puck effect compared to 2mm sword.
I live in Australia where we do not play ice hockey so I do not know the puck shape, mass or what you mean by the "ice-hockey puck effect".

You also need to specify what you mean by a 2mm sword. The wedge angle of a chisle decides if it will jam in a material or bounce out again. The critical angle is the ArcTan( coefficient of friction between material and blade). If the edge angle is too sharp it will jam in the cut which may chip the cutting edge of a thin blade.
 
Baluncore,
In post #7 you can see the ice hockey puck- effect in a skull , and 2mm meaning "thickness of sword". A puck , a rubber disc , is like a blunt object with 90 degree profile . The bi-convex boomerang tip, cutting obliquely along Kaakutja's cortical plate, is like a blunt instrument also. As my first post noted , the angle of a chisel is significant , below 17degrees for softwood. But in cortical bone there is the added effect of random cracking due to thickness above 2mm rather than edge angle.

A boomerang at 5-10mm thickness has twice to five times the front area of a 2mm thickness causing increased resistance. The momentum is placed on a wider section of bone causing deformation compared with severing a thin layer.
This resembles a rowing dinghy's bow- wave compared with a racing yacht , there is more disturbance.
 
When 5mm thick at 10mm back from edge , a boomerang has edge-angle of 30degrees and at 10mm thick it is 60 degrees ( plus the bi-convex curve).
 

jim mcnamara

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It takes exceptional proof to prove an exceptional statement. That is what you are trying to do. So you need "multiple lines of evidence". You do not mention those at all. And you certainly could do a better job on the boomerang problem. IMO.

I think what you are attempting to do is to assert that current interpretation of some fossil evidence of trauma is wrong. Which is okay, go for it. Science works that way.

Consider:
Australian buloke is an extremely hard wood, with a Janka hardness higher than any other commercially available wood. It dulls tool steel. Note the cross grain level is moderate. This increases breaking resistance substantially. Hunting boomerangs are/were often fire treated to increase hardness. You need to show that the force required to sever the required bone thickness can never be generated by a hunting boomerang, forget medical chisels for a while. Buy some dog bones at the grocery and start testing on them with boomerangs made from local really hard wood species. Never underestimate so-called 'primitive' people and their technologies.

Other evidence:

But is there reasonably local evidence from local scientific excavations of iron refining sites or are there any extant iron/bronze/copper tool examples dated to the period in the general locale of the fossil find? Using only the fossil as evidence for something is a great first step. You need corroborating evidence to support your claim.

Local resources to check:
Is there evidence of some 'foreign invasion' of metal working peoples in the relevant time frame?
Sources of metal tools like trading. I.e., is there bog iron nearby? Copper ore nearby ? Nearby might be several hundred kilometers.

Neolithic peoples do not make metal weapons (by definition) and if they do they leave traces like smelting furnaces. So do metal working visitors.

You may be on to something interesting, but it needs lots of work.
 

Baluncore

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A boomerang at 5-10mm thickness has twice to five times the front area of a 2mm thickness causing increased resistance. The momentum is placed on a wider section of bone causing deformation compared with severing a thin layer.
Your use of blade thickness is not rational. It is the cutting edge that penetrates to remove the material. A hunting boomerang is very hard and has a sharp cutting edge. I don't know where you have been getting your data on hunting boomerangs, but they weigh ten times the 170g of an ice hockey puck, and it takes a strong arm to throw one. Maybe the word boomerang is now more restricted to light weight toys that return. The injury to the skull shown was probably caused by a hunting stick (kylie), or a throwing stick. Both can be similar in shape to a returning boomerang, but they are much heavier, fly straight, and are lethal weapons.
 
Jim
"You need to show that the force required to sever the required bone thickness can never be generated by a hunting boomerang ". That's an odd thought . A brick can strike bone but doesn't generate force , the brick-thrower does that. In post#1 the Janke hardness is noted and mulga is similar to buloke. Tests were mentioned in #1. The issue is not medical chisels but the biological nature of cortical bone - it can be cut cleanly by 2mm thick but not by thicker instrument. Boomerangs are made of wood and have to be thicker than 2mm . This is the limit which prevents slicing and causes the ice-hockey style comminuted fractures.

My question remains , where is the evidence in the published articles for wood? Science can't change to fit presumed history.
 
Baluncore,

A heavy kylie is robust but my mulga boomerang weighs 520g , my machete is 580g and Indonesian keris swords are reportedly 300-600g. A kylie is lethal but sharp mulga blades can't fit between cortical plates. The final comment here is interesting:

https://www.abc.net.au/catalyst/stories/4211835.htm
Emeritus Professor Richard Wright AM
. . But whether it's done with a machete or whether it's done with a steel axe or stone axe, I don't know.

Dr Michael Westaway
When you look carefully at these sort of lesions, the striations are fairly diagnostic of an edged steel weapon. So it may actually be evidence for frontier violence. This is significant because we actually haven't seen anything like this in the archaeological record in Australia before.

Dr Michael Westaway
Looking at the experiments on bone that have been published in the United States and elsewhere, we can see that edged weapons, and swords in particular, create traumas very similar to what we're seeing in the man from Toorale.

NARRATION
Bizarrely, the skull wounds on Toorale Man appear similar to those on gladiators in Imperial Rome.

Dr Michael Westaway
It was curious because one of the healed traumas looks very similar to what is documented in an important case study looking at the remains of gladiators. And it looks like a healed trauma from a sword wound.
Dr Michael Westaway
That means that there are weapons being used by people in western New South Wales that are creating signatures that look like, you know, sword wounds.
Badger Bates ( Aboriginal elder)
Our old people back then did not have a blade like that. If that carbon date is 700 years old, there is something wrong somewhere.
 

Baluncore

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A kylie is lethal but sharp mulga blades can't fit between cortical plates.
The cutting edge does not need to fit between the plates. A flake can be created by a square cornered tool at a discontinuity.

@ be unique.
Why do you insist on referring to the cutting edge angle by the blade thickness? Surely “rise over run” represents a wedge angle. Specification of “rise” without “run” is insufficient and certainly not helpful to understanding the cutting process.

I believe you have decided that it must be a metal blade, so you have conducted an opinion pole from the literature, and cherry picked the results. That is not scientific. One incomplete example is an anecdote, it does not constitute a proof. You must find the metal edged weapon that caused the injury, or you must find more examples.
 
Kaakutja shows the inner cortical plate with smooth surface. The blade must have been across the trabeculae, between the plates. If it was thicker than 2mm then it would cause random cracking, not smooth surface. That is why Braun make 2mm thick surgical chisels . Bone anatomy is not optional like MacDonald's customer burgers and this skull is normal.

Where do I say angle is thickness? In post#1 2nd para , thickness is explained.
Blade-angle is relevant to damage but thickness is more so. There are many web examples of blunt force trauma and of sword trauma in skulls. The ice-hockey one is similar ( lighter weight , faster speed) but thicker than sword . There is a difference between excised fractures and comminuted depressed fractures . Textbooks give standard anatomy and standard descriptions of bone behaviour.

Baluncore, do you use a wooden knife , wooden axe or wooden car-frame?
If not , why not?
 
Here are some comments on the response of bone to force:

A technique of percutaneous multidrilling osteotomy for limb lengthening and deformity correction.
Yasui N1, Nakase T, Kawabata H, Shibata T, Helland P, Ochi T.
The bone is drilled percutaneously, using a special drill guide, and osteotomy is accomplished by connecting the multiple drill holes with a small chisel. This technique can prevent undesirable bone cracks.

Orthopedic Hardware - UW Radiology - University of Washington

https://rad.washington.edu/about-us/academic-sections/.../orthopedic-hardware/


Washers are generally used in two situations. They are used to distribute the stresses under a screw head so as to prevent thin cortical bone from splitting.

WO2004089233A1 - Osteosynthesis plate for operative care of bone ...

https://google.com/patents/WO2004089233A1?cl=en


The bore diameter may be reduced relative to conventional holes . On the other hand there is the possibility, based on the location of a fracture to select one of the holes without the risk of a bone crack in the vicinity of the fracture.
---------------

This has graphics of surgery for removing a piece of cortical skull-bone for transplant. Note that the chisels must be thin and carefully moved in sequence to protect the plate from fracturing ( near the end of the page).
The inner plate is thinner so is more liable to be damaged by chiselling.
---------------

https://www2.aofoundation.org/wps/portal/!ut/p/a0/04_Sj9CPykssy0xPLMnMz0vMAfGjzOKN_A0M3D2DDbz9_UMMDRyDXQ3dw9wMDAzMjfULsh0VAbWjLW0!/?approach=Coronal approach&bone=CMF&classification=93-Cranial vault, Cranial vault fractures&implantstype=&method=&redfix_url=&segment=Cranium&showPage=approach&treatment=&contentUrl=/srg/93/04-Approaches/A70_Coronal-approach.jsp

The initial grooves are deepened to the level of the diploë.
The diploë must be visible, which is indicated by cancellous bone bleeding.
..
The outer cortex grafts are separated from the calvarium by sequential advancement of thin osteotomes through the diploic layer.
 

Steelwolf

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Being a historical weapons and armor builder, with a LOT of experience not only in making swords, but in the use of them, as well as having had a father who was a cabinet maker as well as UDT SEAL, so I learned a lot about weapons use and materials etc.

The skull shown on the original paper and NYTimes article appear to be made strictly from the saber-like Wonna, a wooden throwing stick that was also essentially a battle axe if used in hand. Seeing pictures of the weapons possible involved I have to say that with the materials there in the area, where flint and obsidian are extremely rare, mostly being sedimentary type stone for large areas, wooden implements and the specific technology of treatment, fire and plant extracts to harden the material, and having handled some of these implements myself I will state that I find the wounds on the skull in question do not look like wounds that would have come from a metal sword.

They have more the appearance of fast, light impact without the 'carry through' that a dense metal blade would have had, especially in that area for a cut and the fact that there are no other 'cut' marks on any of the bones, especially lower arm defensive wounds. Their description of the 'wonna' a fighting boomerang, makes if fairly clear that was the likeliest weapon to make that wound. Splintering etc on a high-speed impact like that can remove chunks of bone fairly cleanly and even softer wooden implements, used at high speed, can do that kind of damage, high speed being either full man's throw or swing to kill. A hardened chunk of Australian Ironwood will do massive damage.

The reason we do not use wood for knives is their fibrous nature and no edge-holding ability, but the wood is tougher than many metals and not as brittle as most, and lighter so it can be moved at speed. With a weapon speed is more important for a cutting weapon than mass because of the E=M x V^2 with more energy coming from square of speed vs linear of increase of mass. A lighter fast weapon can do more damage than a heavier slow weapon.

Chisels are also for controlled cutting, usually shaving the bone in increments (I well know having had full 2 level fusion at C5-6-7 with multiple laminectomie, which is Why I am no longer making a living building swords.) And when cutting bone or wood with a chisel it is very different than a massive, high energy swing with a sharp club so as to make the comparison not at all comparable.

The hockey puck would do similar damage blasting out a chunk like that even with a 90 degree corner. Without the missing chunk of bone and seeing if it was cleanly split off or shattered would make the determining difference, as well as finding a metal sword in that geological strata and area, or proof of their existence. Without such I think we have to go to the Occam's Razor view of the Wonna being the most likely weapon to cause that damage as it was the indiginous weapon at the time, and the other injuries do not show any sort of edged weapon type marks, and if there was a fight with a sword involved, like that, it would be more evident on Other bones, such as the ribs, which appear to have more of a blunt force trauma to them. The arm injury I am ambivalent on as it could easily be a spalled piece from dull impact, and there is no evidence of edged cut on it even though it appears smooth and conchoidal.

Obviously the individual had survived heavy head wounds before, as there is the healed scars from previous injury to the head. But it looks like the wound to the right side of the skull likely taking out the eye is what killed this man. And it appears to be high speed, low mass impact due to the way the conchoidal edges of the thin side of the flake removed and the apparant crushing of the bone directly under the 'end' of the cut and the piece apparently shattered out of the wound.

But I see no reason to think that it would have been a metal weapon, although there is the distinct possibility of lost sailors having been cast ashore there in Australia, possibly with swords etc, well before Western Colonization. So while there is the slim Possibility of there being a metal sword there the likelihood of it is Low, so I am going to have to back the view that the wound was made by a hardened wood wonna at close range.
 
Hi Steelwolf,
>They have more the appearance of fast, light impact without the 'carry through' that a dense metal blade would have had, especially in that area for a cut and the fact that there are no other 'cut' marks on any of the bones, especially lower arm defensive wounds.

The article agrees with a light-weight weapon. Mulga boomerang , machete and Keris sword are around .5kg. If a wonna cuts a skull then it would make the same arm marks so the absence is how the fight happened.

>Splintering etc on a high-speed impact like that can remove chunks of bone fairly cleanly . A hardened chunk of Australian Ironwood will do massive damage.
Sounds OK on paper . Any evidence for that? 'Massive damage' is not slicing off a flat triangle flap of bone.

> A lighter fast weapon can do more damage than a heavier slow weapon.
Interesting.

>And when cutting bone or wood with a chisel it is very different than a massive, high energy swing with a sharp club so as to make the comparison not at all comparable.
A thick chisel causes cracks, a thin one doesn't . A blunt instrument causes random damage, a sword doesn't.

>The hockey puck would do similar damage blasting out a chunk like that even with a 90 degree corner.
Eh? Kaakutja has no chunk blasted out , it's a flat slice with straight edges.

"The wound to Kaakutja's face and the slice off the humeral head are consistent with a very sharp blade - I am prepared to stand corrected but I would have said that even a very hard wood could not be sharpened to this extent. I could believe the healed linear wound could be a linear depressed fracture which could in theory be produced by a thin sharp hardwood object but the strikes to the face and shoulder would have resulted in fractures and not the fine slices into bone seen here." ( Smith, Martin 2017).Bournemouth Uni ,UK.

"Now I see the full significance of your conclusion ! Martin Smith is a well-known expert so a good endorsement." ( Robertson 2016) Australian Forensics.

The author tested boomerang on pig-skull.
"I have received the following comment from the writer: " The aim of the experiments were to determine whether traditional Aboriginal weapons could have caused trauma similar to that of the Toorale skull. Unfortunately our methods did not produce trauma,.".
School of Archaeology and Anthropology.
ANU College of Arts and Social Sciences, Canberra. "

Neither did my test with sharp mulga boomerang on pig-skull and Synbone. Machete on Synbone gave similar results to Kaakutja , a triangle with straight edges. There had to be reason for the Bronze Age then Iron Age then Chinese steel exports. Here are the suspects:


https://portal-images.azureedge.net/auctions-2018/srdavid10074/images/9f09046d-3220-4208-a5d0-a99100bd3f91.jpg?w=540&h=360
https://www.alamy.com/stock-photo-samburu-warrior-with-a-panga-traditional-short-sword-samburu-national-98194992.html

https://s3.amazonaws.com/productimages.goantiques.gemr/55586714/578737120_fullsize.jpg
 

Steelwolf

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I have Built wooden swords as well as steel ones and bronze, the wood would do exactly that kind of damage, especially the Aussie Ironwood varieties that are used. A pig skull has very different morphology and is NOT a good example of how Human skull would chip/cleave.

While there IS the (Note the exact wording) Possibility of there being a sword in the area, the Likelihood of there being one is extremely low. So, until YOU come up with actual PROOF that that was done by a metal weapon, I am going to continue to insist that that is a wood based impact wound on the skull, that it is chipped and conchoidally edged showing that it was split off from percussive force. That is not a 'sliced' piece, it is broken out of there. It is too bad the missing piece is not there as it would have told us a lot about how that wound was formed, but the wooden wonna appears to be the culprit.

You can post all the Links to stuff you want, I have done the actual work of Doing it. You have presented enough information, such as your talk concerning chisels, to show that you do not know the difference between a tool designed for careful carving of medical materials vs a crude and nasty, high tech as possible, treated wooden weapons As Are Know To Exist in the area at that time.

And yes, weapons have progressed, but a person with a rock can sneak up and kill the guy with all the high tech gear and high powered weaponry, and the stealth and simplicity of a rock is still used today, they do not jam, do not require maintaining.

You seem to be pushing a Theory that has no proof, and, as an expert on this particular subject, even though I do not have the nice little mentor or teacher tags, I ran my own business with the swordmaking for over a decade, and there were many years of playing with knives and using, trying various ones out when I was in the Military and overseas on Guam, PI, Diego Garcia, Perth and Darwin, and yes, I got to see and play with some indiginous weaponry, so I DO know of what I am talking about. Properly treated and hardened wood, when used by a skilled expert, will EASILY leave Cleaving type wounds like that. I could build a sword out of softer wood like Teak that would still take a chunk out of the skull just like that, and the hardened wood Wonna would do the trick quite easily.

As I pointed out before, unless there is a chip of metal left in the skull or the sword itself in the area, and a history, you are not going to be able to CREDIBLY show that this was anything other than a wooden weapon, very expertly used. Wooden Weapons WILL do that kind of damage easily. Most of the world does not get wood as hard as Australian Ironwoods, and yet very durable wooden items have been made and last the ages.

My worry here is that you are coming at this from a point of personal theory and trying to find proofs in the materials and other cutting implements. The real equivalent of this would not be a machete, but an axe, and that would have carried a great deal farther into the skull, so would a machete, although modern machete's are made from rolled steel, and do not have the distally tapered thickness from tang to tip as well as edge thickness and back of sword at the forte. In essence, modern machete is not at all similar to the older swords as it is very high tech alloys (even carbon steel, by comparison, is high tech) and thinner than the older swords. It is not a good stand-in for the era.

So you are trying to compare modern medical chisels to a wooden battle axe, and trying to find modern examples and instead of keeping an open mind, and going where the data leads, you seem to be on a This HAS to be a Metal Weapon Wound, and doing the 19th century thing of pushing the investigation ONLY in the direction of things that You Think are Pertinent because it SEEMS Similar to something else today.

You do the old Aboriginal peoples a great disservice if you are thinking a wooden sword is That inferior to a metal one when those throwing sticks and fighting boomerangs were deadly dangerous and serious.

Besides, you can get similar wounds using something like a thrown dinner plate or ashtray, again it is the speed of the impact giving the extra force vs the weight.
 

Steelwolf

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Why I push the 'Properly made and expertly used' is because wooden weapons get used in a different manner than the metal ones; higher speed for one thing, and they knew the possibility of the weapon splitting or cracking, and would use that as a feature rather than a bug, so they would have a fine rounded edge that could, upon impact, split along the grain and leave a sharper edge than before, the fresh split edge being sharper, IF should it split is is allowed for.

The people took very good care of the weapons and maintained them. Our way of doing things is very different, they were similar to Olympic Athletes, compared to modern man, just for their day to day living, hunting and gathering bands. In some things the expertise has been lost, the ways of making war have not been practiced since the Aboriginal peoples have been conquered and nearly culturally assimilated before allowing them their land and practices back, and war is still forbidden, so there are points that have been lost as far as Man-fighting and weaponry and the skills needed for it.
 
Why do you say it's not sliced ? slice:"a thin, broad piece ". The entry , floor and exit walls are smooth , not "blasted chunk".
The issue is not about modern chisels but how bone reacts . A pigskull is about 1mm thicker than human frontal cortical and is used to replicate shock damage for legal evidence in trials. Synbone is designed to closely replicate human skull and has a thin rubber skin . All the tests by boomerang had the same result. My machete is 1.5mm thick, swords such as Indonesian keris are about 2mm . We can't expect an exact result but the difference between metal ( my garden spade) and boomerang is like chalk and cheese.

"Properly treated and hardened wood, when used by a skilled expert, will EASILY leave Cleaving type wounds like that." Hmmm? Where did you see it?
 

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