Knife vs chain

[Cliff Stamp]

Awhile ago Donna Barnas started a thread on the evaluation of fighting blades and Steve Harvey commented in detail concerning what such a blade should be able to do and how you could look at it :

http://www.bladeforums.com/ubb/Forum3/HTML/001879.html

There were a couple of things that I had never tried and was curious about how stressful they were. I finally managed to get a length of chain (3 feet) and with the help of a friend spent some time beating on a blade.

I first had him try to knock the blade out of my hand, this was in no way possible. I was using a big blade (18") so I had to fight considerable torque, but all it did was knock the blade around a bit, I never felt any slippage. Based on this, I don't see it as remotely possible that a smaller knife like a folder could ever be knocked out of your grip unless you are holding it very loose.

Next I just had him swing the chain starting with low force and working up to a full powered swing and I interscpeted it with the blade. I tried to just stop the chain, and also to deflect it as well as actually reverse the motion. In none of this I was successful, I would assume someone who knew what they were doing might be. End result I concluded that I had no chance to control the chains motion in any significant manner. However I could easily control which part of the blade was going to see the impact so I could protect the edge of the blade.

How was the edge effected? It suffered significant dents. It never chipped, but some of the dents were so severe that the metal was pushed past the plastic deformation limit and then broke away. The most extreme dent was about 0.5" wide and 0.2" deep. At this depth the edge thickness was 0.042. What does this look like -

Some specifics on the steel, the blade is a Barteaux Machete and it is spring steel and left fairly soft (vague I know, no RC available). It is very durable and very resistant to chipping. The damage described above is far less that what I saw on the Ontario machetes on wood. Note as well that I have cut the bevel down to a very thin 6-7 degrees.

Conclusion? If you had asked me before hand to describe the outcome I would have vastly overestimated the damage. I was surprised that the blade held up as well as it did. I didn't expect it to fracture, but given the very acute edge I assumed the dents would have been more severe, aside from the one bad dent, I had seen similar dents just on hard wood chopping. The fact is that unless you tried to actually chop into an incoming object I can't see the blade being damaged much at all, as the picture shows there was only one really bad dent which is when I tried that a few times.

So blocking is out as a cause of this kind of damage as far as I can tell, however if someone was actually skilled at this it would be easily possible for them to exert more control over the incoming object and thus place more stress on the blade. As well there is still the possibilty of you making a cut and someone blocking you with a hard object like a chain or pipe. In this case you could easily create a stituation where the stress would be similar to what caused the large dent.

So is Steves 50% cutting ability after blocking possible? When I first read his post I assumed that it was not in the slightest. However since most "tactical" blades are bevelled *much* more obtuse than the machete, as well as being made out of much stronger steels I now think that yes it is possible. The critical factor would be are they tough enough to handle high energy impacts off of hard contacts and not fracture - I don't know. I have some more blades to experiment with though.

-Cliff

[This message has been edited by Cliff Stamp (edited 08-11-2000).]

 

[Samurai6]

Cool stuff!! Thanks Cliff!

After suggesting testing with a chain, I was rather doubtful myself how many good knives would survive it functioning condition, but perhaps it wasn't too far outside the pale, as they say.

The real life scenario is a surprise attack where someone is swinging a length of chain at your head. You only have time to react reflexively putting your knife and your hand up to block. The block is to save your head, the knife is out front to save your hand somewhat. So the knife takes a beating.

A fracture test with a heavy length of pipe might be the next thing. There should be a number of inexpensive bowie type knives available that I could use for this. For the ultimate test, clamp the knife handle down solidly and beat it with a pipe. I only own expensive big blades right now upon which I am reluctant to do such testing.

Note: these are really tests that makers might do to get an idea of the toughness and strength of their fighting blades. It would be expected to be destructive to a significant extent. A maker might have an edge that cuts like stink but completely explodes when struck by a metallic object, so he might look for an edge grind that is a little stronger, giving up a little cutting efficiency for more strength. The maker could then tell his customers that he developed the grind and heat treatment for this model thusly, so he knows it is a good compromise of strength and cutting for a fighter.

Thanks a lot!

 

[Burke]

Cliff, do you have anything with a harder edge you would be willing to try this with? I wonder if the soft nature of the machete's edge is what saved it from severe damage (i.e., it may have dented in a small area, instead of chipping in a larger one), and if a blade with a harder edge, even if it had a more obtuse bevel, would not fare as well. Just a thought.

 

[Cliff Stamp]

Steve :

A maker might have an edge that cuts like stink but completely explode when struck by a metallic object, so he might look for an edge grind that is a little stronger, giving up a little cutting efficiency for more strength.

Yes you have to decide how much durability will give a functional blade as you can't maximize durability and cutting performance at the same time. It greatly depends on the fighting style of course as Sing pointed out in the last thread.

As for the pipe beating, I have done this on a few cheap blades (Ontario machete) and found that I could hit them with a maul (8-10 lbs) about 100 or so times (90 degree, light swing), with them on concrete before they broke. This seems respectable to me as in combat the blade will move with the hit and thus "absorb" some of the impact energy that way. The crucial question to me is how many high energy hits does a fighting blade need to be able to take in modern times?

Burke, you are exactly right in that the high toughness of the machete prevented it from suffering extreme damage because of fracture, and that yes, steels can vary widely in impact toughness (well over 100%) and thus even an obtuse bevel on a brittle steel will not prevent failure. I have a couple of really nice blades that cut very well but if I struck them with the chain I would strongly bet the whole blade would crack in half, they are not "combat" blades though.

How does a stronger steel fare? Here is a shot of a 15" AK from HI after many hits with the chain (also shown) :

http://www.physics.mun.ca/~sstamp/images/chain_ak.jpg

I had a friend hit the blade several times and as well I tied the chain to the bottom of the front porch and hacked away at it about a dozen times. The Ang Khola suffered much less damage than the machete. It took more impacting near the tip, which is sensible as the hardening is not uniform, the edge is softer as you go towards the tip.

What was impressive is that in the chopping area, in only one place did the edge actually take perm. damage. The other dents did not actually remove the metal and I could hammer/push them back into place. In that one place where the edge broke away I figure that the khukuri bit into the chain deep enough so that when it twisted it snapped around the edge and broke it off. Unlike the machete, the khukuri could cut into the chain and did so on every hit, for example :

Some shots of the AK amd machete together :

Some specifics on the 15" AK, it is forged spring steel, edge quenched. The edge is defined by a convex bevel, with a very low curvature, it is very close to a 14 degree flat grind, decently acute. The worse impact was about 0.15" wide, and about 0.065" deep at which point the metal was 0.038" thick, this was one of the tip impacts.

Based on the performance of the khukuri it now seems likely to me that a steel with similar toughness but much stronger (3V) with a decently obtuse bevel, convex with a decent curvature (say a filled out 25-35 degree flat bevel), might be able to resist fracture and deformation to the extent that the damage would not be visible. When I get my Battle Mistress back I will see how that fares, I might have to reprofile it as now the edge is relatively thin.

-Cliff



[This message has been edited by Cliff Stamp (edited 08-12-2000).]

 

[sing]

Cliff,

Very interesting stuff!

I have a brand new Ontario Frontiersman with the Bagwell bowie designed blade. This blade is, however, thinner than 1/4" stock on the Ontario Bagwell line and is of "high carbon" steel (whatever that might be... Anyone know?) I am planning to test that against another bowie at the end of the month. After that test, I will try some steel pipe against blade to see what will happen.

Will update in September.

sing
AKTI #A000356

 

[Burke]

sing, I believe the steel in the Ontarios is 1095.

 

[Brian Jones]

Cliff,

In terms of tactical, try it again and this time have the guy wallop you right on the hand with the chain, and see how effective the knife is on the ground with your hand broken!

Just kidding -- please don't do that.

Seriously, that was a very interesting and useful test, and thanks for always sharing your work with us!

Best,

Brian.

 

[Will Kwan]

Steve,

How often do you expect to have to block a chain in an engagement? Typically, does the chain wrap around the knife and impact the blade multiple times?

Cliff,

Do you think repeated beating stresses the steel so that the blade fails suddenly, without warning. I am thinking that with the right blade geometery and heat treat the edge might not show much damage but develop internal stresses or microscopic fractures (similar to craze cracking).

Will

 

[Samurai6]

Will,

I don't ever expect it, it was just a way for a maker to know how his fighter or tactical knife would hold up under the worst case scenario. A maker might well decide that he couldn't make a knife that would both cut aggressively enough and pass the chain impact test, in which case he would simply disregard it. It was just an idea off the top of my head, the worst thing you might hope a fighting knife would live through and still function.

If anything like that ever happened to me, and I survived, I would probably retire the knife and get another one just like it, thanking the maker for building the blade that saved my melon.

 

[Cliff Stamp]

Will :

does the chain wrap around the knife and impact the blade multiple times?

The chain I was using was far too stiff for that to happen, I would get one impaction on the edge per hit. If the chain was much lighter so it could be swung faster, and had smaller links, then this could be possible. However with that type of chain the impact energy would be much lower as only a very localized part of the chain actually effects each impact.

I am thinking that with the right blade geometery and heat treat the edge might not show much damage but develop internal stresses or microscopic fractures

Yes this would happen. Basically if you are above a certain threshold level, repeated stresses will eventually cause failure due to fatigue. For example I broke two machetes (1095, Ontario) in half by hitting them lightly with a maul. The individual impacts themselves did not cause any visible damage but after 100+ hits the blade cracked in half. You would never be able to do this if you used a much softer maul (rubber, say) because the individual impacts are not above the threshold level. They cannot cause a perm. effect so they don't "add up".

I have seen the same thing happen in much lower stresses it just takes longer. On wood the cycles are much higher, the lowest I have seen was about 500 hits into hardwood with an RCM from Livesay, damage to about 1 cm in depth. A low-medium range example would be the Ontario machetes which were able to take almost two sessions of cutting before they suffered significant edge fracture (1/2" depth) , in the 2-3 thousand impact range. For a really high example, the Busse Battle Mistress took well over 10 k hardwood impacts before the edge was that weakened the durability was low enough that further light stress impacts could produce visible damage of sub-mm depth.

Steve :

the worst thing you might hope a fighting knife would live through and still function.

Yes, there are a couple of very broad ranges of durability :

1) the blade fails suffering gross failue, ex., it snaps in half

2) the blade suffers extreme edge damage, say 1/2" in depth, not possible to restore

3) the blade suffers light chipping, or slightly more extensive denting, but 90-100% restoration is possible]

4) the blade suffers no visible damage and just needs to be sharpened

Case 1 you want to avoid obviously. Case 2 is a one fight blade as you are still left with a very dangerous weapon - however if the fight is extended it will not be for long if the impacts are repeated. Is this a possible senario - I don't know? Case 3 and 4, well, at the end of the fight you either have to drop the maker a line or break out a hone - as Steve said, considering the possible consequences I don't think that even Case 3 is going to be a let down.

There is a possible Case 5, in which the blade takes no damage and doesn't even need to be sharpened, but I simply don't think you can get that level of hardness, strength and toughness at the same time - and of course still be able to cut something. I would be extremely interested if a maker thought he could though.

The two blades I used are case 3 examples, the Barteux defining the lower limit (any worse and you are going to be case 2) and the khukuri the upper (any better and you are going to be case 4). Somewhat vague, I know, but a starting point.


-Cliff


[This message has been edited by Cliff Stamp (edited 08-17-2000).]

 

[Will Kwan]

I don't know what kind of chains one really expects to face. I suspect drive chains such as for a motorcycle or bicycle might be common. I wonder how the knife would fair against these chains as they are probably heat treated. While the drive chain is probably harder, there are considerably lighter.

Will

 

[Cliff Stamp]

Will :

I wonder how the knife would fair against these chains as they are probably heat treated. While the drive chain is probably harder, there are considerably lighter.

I would guess that they would pose far less of a threat to the blade in terms of damage dealt. The interesting thing is that unless the object being struck is soft enough for the blade to bite in, you can't get the hard snaps across the blade face that are what cause the maximum damage. This is why that relatively soft staples can cause more damage than harder ones on utility knives - at first glance not what you might expect.

If I get a hold of some lighter chains I'll try them out on the same blades and others to see how they fare. I also have a couple of pieces of flat stock (M2, hardened) which I will put a more "tactical" bevel on (say 25-35 degrees) and see how it fares.


-Cliff

 

[Snuffy]

I'm reminded of the Japanese martial technique of "manriki gusari" (loosely translated as the "chain with the power of ten thousand"). I think it was developed by a guardsman at a temple gate - he saw many fights develop in the crowd seeking admittance to the shrine, and didn't want to draw his sword, causing unneeded bloodshed. He came up with the "manrikigusari", a chain about three feet long, with lead/iron weights about 4-5 inches long at each end.

According to what I've heard, this style developed techniques against empty hands, knives and long and short swords - does anyone here know more about the techniques and their application to fighting?

 

[rep]

My experience with chains is that they come at a person rather fast and strike over a wide area. They break bones and damage tendons and such. As such, chains are rather difficult to block. Running away is good.

 

[Matt Shade]

You could always shoot the guy holding the chain too

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It'll feel better when it stops hurting.