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Battle Rat block chop,could most knives do it and survive?
- Thread starter jra111
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Cliff Stamp
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Edge geometry is a factor but hardly the only one. Blades with very thick edges can still fail grossly due to lack of impact toughness or strength. I have seen AISI 420 bowies take dime size blowouts on knots, let alone concrete as the steel is too soft regardless of the thick edges.
On a higher end, consider how the WB (Strider) and 52100 bowie (Ray Kirk) handled it. The WB had a far thicker and more obtuse edge than the bowie but still took far more damage because of the huge difference in impact toughness between 52100 and ATS-34 :
http://www.physics.mun.ca/~sstamp/knives/WB.html
To do this well, and handle inclusions in general, you want a high hardness to resist excessive impaction, a high strength to resist lateral denting, and a high impact toughness and ductility to resist fracture. This can all be found in a spring steel like 5160, or any of the low alloy carbon steels like 52100, L6 etc. . Toughness is the critical factor as there can be differences of 10x or more among steels and thus this can swamp out very large geometry differences.
The Swamp Rat knives do not have the very slim edge geometry of a Marbles, but they are not the heaviest edges out there, from what I have seen, Strider, TOPS and Livesay are all thicker as are most custom tacticals from the specs the makers quote. The Ray Kirk knife, had a geometry easily equal to any knife, Marbles included and was not grossly damaged. It did take more damage than the Swamp Rat line, but this is to be expected as it is slightly softer, and the edge is much more acute.
-Cliff
On a higher end, consider how the WB (Strider) and 52100 bowie (Ray Kirk) handled it. The WB had a far thicker and more obtuse edge than the bowie but still took far more damage because of the huge difference in impact toughness between 52100 and ATS-34 :
http://www.physics.mun.ca/~sstamp/knives/WB.html
To do this well, and handle inclusions in general, you want a high hardness to resist excessive impaction, a high strength to resist lateral denting, and a high impact toughness and ductility to resist fracture. This can all be found in a spring steel like 5160, or any of the low alloy carbon steels like 52100, L6 etc. . Toughness is the critical factor as there can be differences of 10x or more among steels and thus this can swamp out very large geometry differences.
The Swamp Rat knives do not have the very slim edge geometry of a Marbles, but they are not the heaviest edges out there, from what I have seen, Strider, TOPS and Livesay are all thicker as are most custom tacticals from the specs the makers quote. The Ray Kirk knife, had a geometry easily equal to any knife, Marbles included and was not grossly damaged. It did take more damage than the Swamp Rat line, but this is to be expected as it is slightly softer, and the edge is much more acute.
-Cliff
I would personally never chop a a brick but it just was impressive. I was debating on on the battle rat or the bk9 and was debating if the price is worth it . The warentee is good for the battle rat, But Steve Harvey are you saying the battle rat is just a big chopper thats probobly not good for other stuff because its so thick?
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jra111,
Cliff's idea of gross damage and mine differ hugely.
I don't know anything about the edge geometries of the Battle Rat or the BK9, but both are made out of medium to low alloy steel - we are not comparing ATS-34 and 52100 here - and I am certain that the biggest determining factor in any performance difference between the two knives in question while chopping through a cinder block would be edge thickness, period.
Cliff himself asked the most important question in the block chop thread. Will the Battle Rat cut through a piece of rope without having to stand on it?
That is the question. If it will, then it is a damn fine big blade, but just smashing a cinder block and making a one inch slice into a piece of paper are not enough evidence for me. Which is the better blade, I do not know, but I would never make the judgement based on a stunt like chopping up a cinder block. Now if the knife could perform impressively on free hanging rope, or on a wood chopping test, then survive the cinder block event so well, that would be something. But the simple fact is that there probably isn't that much difference in the performance of the two steels these knives are made of, and that only leaves edge geometry to determine which will cut better and last longer.
Jerry Busse made the best commentary on gross abuse of knife edges in the guise of testing that I have seen. He took one of his big custom INFI blades and a small finer edged shop knife made out of something else, like A2, and he smashed them together edge to edge. Guess what, they were both damaged. Jerry did this to illustrate the point that destructive testing doesn't tell you much that is of any use.
Cliff's idea of gross damage and mine differ hugely.
I don't know anything about the edge geometries of the Battle Rat or the BK9, but both are made out of medium to low alloy steel - we are not comparing ATS-34 and 52100 here - and I am certain that the biggest determining factor in any performance difference between the two knives in question while chopping through a cinder block would be edge thickness, period.
Cliff himself asked the most important question in the block chop thread. Will the Battle Rat cut through a piece of rope without having to stand on it?
That is the question. If it will, then it is a damn fine big blade, but just smashing a cinder block and making a one inch slice into a piece of paper are not enough evidence for me. Which is the better blade, I do not know, but I would never make the judgement based on a stunt like chopping up a cinder block. Now if the knife could perform impressively on free hanging rope, or on a wood chopping test, then survive the cinder block event so well, that would be something. But the simple fact is that there probably isn't that much difference in the performance of the two steels these knives are made of, and that only leaves edge geometry to determine which will cut better and last longer.
Jerry Busse made the best commentary on gross abuse of knife edges in the guise of testing that I have seen. He took one of his big custom INFI blades and a small finer edged shop knife made out of something else, like A2, and he smashed them together edge to edge. Guess what, they were both damaged. Jerry did this to illustrate the point that destructive testing doesn't tell you much that is of any use.
Cliff Stamp
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Steve Harvey :
Edge angle would be more critical than thickness, however, geometry aside, there is a large difference in how the steels perform based on my experience with several Camillus knives under high impacts and the performance testing done by Busse.
Busse does rope and wood chopping with his blades, not just simply cutting demonstrative of inclusion impacts, and doesn't stand on them to cut with them, or hasn't when he has done public testing of this nature. Which considering his, ahem, stature, would be a feat in and of itself.
The cutting ability of the Swamp Rats was described well in a review by Andrew Lynch a short time ago :
http://www.swampratknifeworks.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=10;t=000063
-Cliff
Edge angle would be more critical than thickness, however, geometry aside, there is a large difference in how the steels perform based on my experience with several Camillus knives under high impacts and the performance testing done by Busse.
Busse does rope and wood chopping with his blades, not just simply cutting demonstrative of inclusion impacts, and doesn't stand on them to cut with them, or hasn't when he has done public testing of this nature. Which considering his, ahem, stature, would be a feat in and of itself.
The cutting ability of the Swamp Rats was described well in a review by Andrew Lynch a short time ago :
http://www.swampratknifeworks.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=10;t=000063
-Cliff
Cliff:
Exactly. Which is why they are my favorite choice (especially 5160) for a real hard use blade. But I don't think steel choice can swamp out edge geometery to the extent that your other statement implies.
I have a Micarta handled Marbles Loveless Sport 99 in 52100 that had an equisitely thin edge, it would sclice though a beef tenderloin to make medallions with almost no felt pressure. While doing some light cutting on a wood and nylon (the wood is on the outer area, nylon in the middle) on a stale french baguette to make into croutons.
I saw edge damage (minor chipping (and here is the real suprise) rolling. Since rolling and chipping are signs of different types of failure (low strength v. low toughness) this suprised me.
To make a long story short, I reground the edge and lost some metal, then reconvexed it. It has a slightly thicker edge, doesn't cut as well, but is far more durable.
I suspect the problem was decarbuarized metal at the edge, or in the alternative that marbles detempted a small part of the edge during sharpening. Either way the problem is fixed now, and the knife peforms much better.
To reiterate this was cutting bread, yes very (rock) hard bread, which BTW made great croutons for french onion soup, but strange.
There are so many factors that determine the feasablility of a design, the steel selection, primary grind and edge geometery, heat treatment, etc, that it is a combination of factors that make a design work well for a chosen task, one can not be singled out as the dispositive or determinative factor.
In any event, this has the possibility to turn into an interesting thread.
So I pose this question (with the cavaet that I am a Busse fan) what does chopping a concrete block have to do with real world use, if that is my task a pick/ sledge hammer will do the job far more effectively.
Does anyone think that a real life use can be extrapolated from the performance of knives on concrete? (well maybe if you are a mason
)
FWIW the last ime I used a knife to break cinder blocks it was an HI BAS and I used the spine, the cinder blocks simply shattered at the impact, though they were old and crumbling. The HI was fine.
Exactly. Which is why they are my favorite choice (especially 5160) for a real hard use blade. But I don't think steel choice can swamp out edge geometery to the extent that your other statement implies.
I have a Micarta handled Marbles Loveless Sport 99 in 52100 that had an equisitely thin edge, it would sclice though a beef tenderloin to make medallions with almost no felt pressure. While doing some light cutting on a wood and nylon (the wood is on the outer area, nylon in the middle) on a stale french baguette to make into croutons.
I saw edge damage (minor chipping (and here is the real suprise) rolling. Since rolling and chipping are signs of different types of failure (low strength v. low toughness) this suprised me.
To make a long story short, I reground the edge and lost some metal, then reconvexed it. It has a slightly thicker edge, doesn't cut as well, but is far more durable.
I suspect the problem was decarbuarized metal at the edge, or in the alternative that marbles detempted a small part of the edge during sharpening. Either way the problem is fixed now, and the knife peforms much better.
To reiterate this was cutting bread, yes very (rock) hard bread, which BTW made great croutons for french onion soup, but strange.
There are so many factors that determine the feasablility of a design, the steel selection, primary grind and edge geometery, heat treatment, etc, that it is a combination of factors that make a design work well for a chosen task, one can not be singled out as the dispositive or determinative factor.
In any event, this has the possibility to turn into an interesting thread.
So I pose this question (with the cavaet that I am a Busse fan) what does chopping a concrete block have to do with real world use, if that is my task a pick/ sledge hammer will do the job far more effectively.
Does anyone think that a real life use can be extrapolated from the performance of knives on concrete? (well maybe if you are a mason
)FWIW the last ime I used a knife to break cinder blocks it was an HI BAS and I used the spine, the cinder blocks simply shattered at the impact, though they were old and crumbling. The HI was fine.
Gollnick
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At the recent Bladeshow, I happened to be walking by some exhibit (I won't name the company since I don't seek to spark any discussion of the knife) and they were showing a video of someone using their knife to chop a cinderblock in half.
My response was, "If I'm ever attacked by a cinderblock, that's the knife I want!"
The fellow I was walking with happens to be a highly trained martial artist. His response was, "I can chop up a cinderblock with my bare hands and it'll only take me one hit."
So, we were, overall, unimpressed with this demo. :yawn:
My response was, "If I'm ever attacked by a cinderblock, that's the knife I want!"
The fellow I was walking with happens to be a highly trained martial artist. His response was, "I can chop up a cinderblock with my bare hands and it'll only take me one hit."
So, we were, overall, unimpressed with this demo. :yawn:
Cliff Stamp
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chad :
For most normal use, it mainly is directly related to how a knife handles hitting inclusions in materials as well as hidden objects, generally only a significant concern for larger chopping knives obviously. While using martindale machetes this last few weeks I chopped into screws (had rusted off and cracked inside the wood), and hit rocks twice while clearing some heavy ingrown vegetation. .
In fact I chopped up a few hundred pieces of scrap lumber last week which were used to set foundations which had concrete on them. I did knock the worse of it off before I chopped it up to burn. But I didn't take a scraper and scrub it clean simply because I knew it would take less time to resharpen the knife after the work was done than it would to clean the wood.
In order to avoid such incidents it is necessary to use bark peelers before you fell trees, beaters before you cut vegetation, run metal detectors on the wood (you can't always see nails because they can get ingrown, or idiots can spike them in with nail sets), etc.. This would seem to me to be far less realistic for usage in general and would be an example of too highly constrained testing and hardly field use, unless this is the method advocated which I have never seen anyone do so.
To clarify, I do most of the precautions in the above the vast majority of the time. Some times though, you slip up and even when you don't things can still go wrong. I had a bad break awhile ago when the wood around a knot broke badly and an axe glanced and slammed into a rock. The frequency of this is low (only twice this year), but it will happen eventually if you chop enough.
-Cliff
For most normal use, it mainly is directly related to how a knife handles hitting inclusions in materials as well as hidden objects, generally only a significant concern for larger chopping knives obviously. While using martindale machetes this last few weeks I chopped into screws (had rusted off and cracked inside the wood), and hit rocks twice while clearing some heavy ingrown vegetation. .
In fact I chopped up a few hundred pieces of scrap lumber last week which were used to set foundations which had concrete on them. I did knock the worse of it off before I chopped it up to burn. But I didn't take a scraper and scrub it clean simply because I knew it would take less time to resharpen the knife after the work was done than it would to clean the wood.
In order to avoid such incidents it is necessary to use bark peelers before you fell trees, beaters before you cut vegetation, run metal detectors on the wood (you can't always see nails because they can get ingrown, or idiots can spike them in with nail sets), etc.. This would seem to me to be far less realistic for usage in general and would be an example of too highly constrained testing and hardly field use, unless this is the method advocated which I have never seen anyone do so.
To clarify, I do most of the precautions in the above the vast majority of the time. Some times though, you slip up and even when you don't things can still go wrong. I had a bad break awhile ago when the wood around a knot broke badly and an axe glanced and slammed into a rock. The frequency of this is low (only twice this year), but it will happen eventually if you chop enough.
-Cliff
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I think INFI really is the best steel on the market for a big chopper,Busse really has something there.I'm curious though why Swamp rat exists...with the backlog and delivery delays we've all heard about why start another company to build less expensive knives out of inferior(to INFI) steel? Doesn't make any sense to me unless they're being made by somebody else.If you had exclusive use of the best steel on the planet would you use anything else?I don't think anyone knows how much difference in performance there is between a battle rat and a BK9,the first production knives of both models have just recently hit the streets!What we do know about these steels is that they are very similar,both are essentially a modified 52100 according to what I've read here on BFC.And regardless of any minor differences we're talking about simple carbon steel that's reasonably forgiving of heattreat from two different makers who both know how to heattreat steel.one probably has an edge over the other in some area and vice versa.If I'm wrong about any of this let me know,I'm no metallurgist,just a guy who likes to use knives...as far as the cinder block test goes I think the becker would give similar performance,simple honest carbon steel usually does very well in such tests.
Eric Isaacson
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Originally posted by Gollnick
My response was, "If I'm ever attacked by a cinderblock, that's the knife I want!"
The fellow I was walking with happens to be a highly trained martial artist. His response was, "I can chop up a cinderblock with my bare hands and it'll only take me one hit."
So, we were, overall, unimpressed with this demo. :yawn:
I'm also a Martial Artist and I also happen to know something about the knife that performed this test. The knife CUT through the block, not smashed it as I would if I were using my hands. Yes, I have broke concrete blocks with my hands, I've also cut through one with a knife. There is a significant difference.
The test was performed to show how a knife would react to inadvertent contact to rocks, stone and bones while using it in the real world. It would not be my first choice if I had to break up a sidewalk, however, it would fair much better than most.
You guys might want to read the whole thread over on the Rat Chat forum, there is a lot of good info. http://www.swampratknifeworks.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=10;t=000048
Also to clarify, the edges are not thick and you don't need to stand on them to cut rope. It can handle free hanging rope and boards etc without any problems and still CUT through a concrete block without damage.
There is something else missing here, SR101 is a variation of 52100, but no one is heat treating knives like what is being done on this line. This has increased the performance of 52100 substantially.
Brent,
The reason for the Swamp Rat line is to offer a Extremely High Performance Blade and at an Economical price that LEO, military and the basic outdoorsman can afford. This is something that has been lacking in the knife industry. The Swamp Rat line will fill that niche.
My whole reason for asking is that if you are chopping and ping a rock,nail or what ever and you chip out a piece of metal that makes the knife useless to where you have to replace it . Then 2 BK9's would be $120 but one Battle Rat would be $150 and be replaced no questions asked. If the BK9 could handle similar amount of abuse and most likely would never need replacement then I can save myself $90.
I dont have any experience really with blades bigger than 7 inches my self. I like the appeal of these bigger blades though. From what I have read in all these forums the Busse/swamprat knives are more of a work horse/chopper and the BK9 is more of a chopper that handles the finer work better. Im looking at both still but its also hard not having held either.
I dont have any experience really with blades bigger than 7 inches my self. I like the appeal of these bigger blades though. From what I have read in all these forums the Busse/swamprat knives are more of a work horse/chopper and the BK9 is more of a chopper that handles the finer work better. Im looking at both still but its also hard not having held either.
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THAT is why I can appreciate that test. Getting into a knot when you're chopping, a big rock that you just didn't see, or a brick hiding in the leaves with your edge when you're clearing off brush, and suddenly all that "unrealistic" testing gets put into perspective (and all of those things happened to me this spring, just working in the back yard).
Eric:
I agree 100%, as you well know but other readers may not, Jerry Busse built his name by selling nuclear tough knives to those who needed them, soldiers, sailors, marines and public service personel. Unfortunately the price of the custom line is too high for many of these underpayed professions to afford, yet they are staking there life on there gear, as well as the lives of those they serve and protect.
The Basic line in M-INFI was a great choice for these people, but alas is no more, because of materials problem (too expensive to produce M-INFI for the mill IIRC).
There has been a huge outcry from Busse fans to bring back the BAsic Series, myself included in that group. (There is also a bigger cry for "The Folder" ) Busse responded to the pleas of consumers by announcing the new SR line.
The Basic series offered an incredible level of performance for the price, if the SR line matches this high standard, then they will be great knives indeed.
Cliff:
Do you think that hitting a nail while chopping into wood is really comparable to chopping cinder blocks? While it is more comparable than say, slicing rope, it is not IMHO a valid inclusion test.
While the initial damage caused by nail inclusions is greater because of the concentration of force on the edge(and I know these all to well) it is also highly localized.
With chopping concrete, you may not see the same level of immediate damage, I believe there will be extensive microcrack propegation setting the steel up for massive failure down the road. It is the same effect as you have seen chopping wood with ATS34 blades for long periods of time, just accelerated.
Some knives will fail right away, because of the severity of the test, or grind or a heat treat not optimized for chopping. My Sebenza or TTKK (both BG42 at a high RC with thin edges and acute grinds) would certainly see instant damage. A spring steel blade may have less damage in the short run, but the stresses caused by the tests will cause failure in the long term, and that failure will come while performing tasks not normally stressful enough to phase the knife.
As we have discussed before, this effect may be lessened to a degree by destressing the blade (bringing and holding the blade at a temp some 50-100 degrees below temper point.)
Take care,
Chad
I agree 100%, as you well know but other readers may not, Jerry Busse built his name by selling nuclear tough knives to those who needed them, soldiers, sailors, marines and public service personel. Unfortunately the price of the custom line is too high for many of these underpayed professions to afford, yet they are staking there life on there gear, as well as the lives of those they serve and protect.
The Basic line in M-INFI was a great choice for these people, but alas is no more, because of materials problem (too expensive to produce M-INFI for the mill IIRC).
There has been a huge outcry from Busse fans to bring back the BAsic Series, myself included in that group. (There is also a bigger cry for "The Folder"
) Busse responded to the pleas of consumers by announcing the new SR line.The Basic series offered an incredible level of performance for the price, if the SR line matches this high standard, then they will be great knives indeed.
Cliff:
Do you think that hitting a nail while chopping into wood is really comparable to chopping cinder blocks? While it is more comparable than say, slicing rope, it is not IMHO a valid inclusion test.
While the initial damage caused by nail inclusions is greater because of the concentration of force on the edge(and I know these all to well) it is also highly localized.
With chopping concrete, you may not see the same level of immediate damage, I believe there will be extensive microcrack propegation setting the steel up for massive failure down the road. It is the same effect as you have seen chopping wood with ATS34 blades for long periods of time, just accelerated.
Some knives will fail right away, because of the severity of the test, or grind or a heat treat not optimized for chopping. My Sebenza or TTKK (both BG42 at a high RC with thin edges and acute grinds) would certainly see instant damage. A spring steel blade may have less damage in the short run, but the stresses caused by the tests will cause failure in the long term, and that failure will come while performing tasks not normally stressful enough to phase the knife.
As we have discussed before, this effect may be lessened to a degree by destressing the blade (bringing and holding the blade at a temp some 50-100 degrees below temper point.)
Take care,
Chad
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I agree it's impressive and useful information,I don't believe that a quality knife made of 5160 or similar would have much trouble with it.A concrete block is not the same thing as a rock,it's not the same thing as concrete either,they're made to be strong in compression while staying as light as possible(air entrained) to make it easier on the mason.they're made of sand and fly ash and a little cement.I've cut enough of them with my plain old cheap carpenters chisel to know.I think it's a great test of a blade,but I don't think the Rat is the only knife that can do it!I'm sure the rats are great knives,worth the money,my basic 9 sure was.But I wouldn't base a decision on those results.If at all possible hold the knives in your hand and see which one feels the best to you,or buy them both and sell whichever one you don't like here on BFC,or better yet,keep them both!the BK9 is a bit lighter,which should make it a little easier to do fine work with,some love the handles,some hate them.I've never heard of anyone being unsatisfied with a warranty issue on a becker,even Cliff got a patrol machete replaced and he is well known in the knife world as a destructive tester...
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Given the same edge geometry, I'm not sure if a BK9 could or not (chop through the block with little affect to the edge). If I had to guess, I would say not. A cinder block seems to be an easier substance to chop through than most rock, but it doesn't negate the results of the tests (Swamp Rat tests). The results, IMHO, are still very impressive.
Such tests are highly relevant to me. While chopping, I quite often hit hard objects, mostly rock. Be it because the rock was hidden in grass or brush I was clearing, due to a glanced blow from wood chopping, or because a piece of wood I was chopping gave way unexpectedly easily and the knife continued into a rock, the edge takes a lot of abuse. It is nice to know that a knife can stand up to such abuse.
Such tests are highly relevant to me. While chopping, I quite often hit hard objects, mostly rock. Be it because the rock was hidden in grass or brush I was clearing, due to a glanced blow from wood chopping, or because a piece of wood I was chopping gave way unexpectedly easily and the knife continued into a rock, the edge takes a lot of abuse. It is nice to know that a knife can stand up to such abuse.
AKADave
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While impressive that test is about as valid as using a gun to hammer nails and then see if it can still shoot. I cant think of a scenario where a person is going to need to use a knife for that purpose and if they do they are likely to not care what condition the knife is in when they are done and would likely discard the knife.
Ebbtide
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I'm with AKADave
How about driving you car into a brick wall to see how it stops?
If you're concerned about hitting rocks while chopping, test with a rock.
If you're worried about hitting a nail that has been hidden away in a tree for years....
Hammer a nail into a log and test it.
Me?
I don't chop with my knives, then again, I don't open packages with my keys either
How about driving you car into a brick wall to see how it stops?
If you're concerned about hitting rocks while chopping, test with a rock.
If you're worried about hitting a nail that has been hidden away in a tree for years....
Hammer a nail into a log and test it.
Me?
I don't chop with my knives, then again, I don't open packages with my keys either
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.Given the same edge geometry, I'm not sure if a BK9 could or not (chop through the block with little affect to the edge). If I had to guess, I would say not. A cinder block seems to be an easier substance to chop through than most rock, but it doesn't negate the results of the tests (Swamp Rat tests). The results, IMHO, are still very impressive.
I actually did chop a cinderblock with a BKT Brute.(.050-.060 thick edge) No big deal. Didn't really hurt the edge at all. The hammer head at the back of the blade does a much better job of breaking blocks I might add.
A cinder block isn't much of a test. Their shape rather than their material is what gives them their strength. Cinder is the key word here. They are partially made up of CINDERS, better known as ashes.
The random pebble is what gets you in a cinderblock, not the spongy sand/water/ash/ carrier. Will chopping a bag of concrete chip your edge? No, neither will a cinder block unless you hit a random rock.
It seems that chopping compressed dust may be a new marketing trend, who knows?
I havent gotten a BK-9 yet, but I am reasonably sure someone will try this stunt.I consider on the same carnivalesqe level as the "bolt cutting" test perpetuated by Buck for many years.
I would measure the edge thickness prior to the chop, the BK-9 seems thinner at the edge (I would guess .030-.040) than the swamp rats I saw at Blade.
I say if you want to compare the performance of the Swamp Rat to the CU-9, do it head-to-head, on the same day, the same tests, with the same testers and take pictures. Enough with the historical comparisons or the "in my opinions". In my opinion, those statements don't hold a heck of a lot of water.
I actually did chop a cinderblock with a BKT Brute.(.050-.060 thick edge) No big deal. Didn't really hurt the edge at all. The hammer head at the back of the blade does a much better job of breaking blocks I might add.
A cinder block isn't much of a test. Their shape rather than their material is what gives them their strength. Cinder is the key word here. They are partially made up of CINDERS, better known as ashes.
The random pebble is what gets you in a cinderblock, not the spongy sand/water/ash/ carrier. Will chopping a bag of concrete chip your edge? No, neither will a cinder block unless you hit a random rock.
It seems that chopping compressed dust may be a new marketing trend, who knows?
I havent gotten a BK-9 yet, but I am reasonably sure someone will try this stunt.I consider on the same carnivalesqe level as the "bolt cutting" test perpetuated by Buck for many years.
I would measure the edge thickness prior to the chop, the BK-9 seems thinner at the edge (I would guess .030-.040) than the swamp rats I saw at Blade.
I say if you want to compare the performance of the Swamp Rat to the CU-9, do it head-to-head, on the same day, the same tests, with the same testers and take pictures. Enough with the historical comparisons or the "in my opinions". In my opinion, those statements don't hold a heck of a lot of water.
Cliff Stamp
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Chad :
Inclusions, such as the nails are far worse. The concrete is made up out of sand, cement and rocks. The sand and cement are not hard enough to damage a knife beyond blunting (damage you can't see side on at arms length). What does the damage in the concrete blocks are the rocks which are essentially inclusions in the much softer concrete. The surrounding sand and cement lessen the damage as compared to just chopping the rocks or other inclusions alone. Here are a few shots of the CU/7 to illustrate :
http://www.physics.mun.ca/~sstamp/images/cu7_concrete.jpg
http://www.physics.mun.ca/~sstamp/images/cu7_nail.jpg
The first shows the damage from 150 concrete chops (middle part of blade), and 15 nail hits (3.5" common nail, drove half way into a 4x4 and chopped into - straight down until the nails bent over or broke out). The blade was not recurved before the chopping, this is metal loss. The second shot is a blow up of the nail hits showing how they broke out sections of the edge with each conteact, fracture, not deformation. The concrete block chops did a lot of impacting as the pressure was reduced by a factor of about 10 over the nail contacts (length of contact region).
Damage will indeed be induced later on due to stresses in the blade, however these will be greater for the nail impacts due to the much higher pressures induced, same goes for inclusions in general, assuming a similar number of chops for each one of course. The concrete block chop can as well of course be compared directly to impacts right off of concrete, rocks, or other large objects accidently chopped into while clearing heavy cover. As well as having to cut through very dirty materials or metals in extreme cases, simply concrete covered wood or similar. It can also just be used to directly compare issues such as impaction resistance, ductility and impact toughness from blade to blade, or steel to steel.
Details :
The nail impacts and the concrete damage was limited to steel under 0.025" thick. I regound the edge with a steeper bevel (18 degrees per side), and repeated the cutting. Again the edge behaved in a similar manner, damage was limited to steel less than 0.025" thick. With the more obtuse angle, this of course restricted the damage depth. The chops were done at full force, the blocks were shattering upon impact one out of every 4-5 hits. If you want to compare this to the Swamp Rat pictures, note that the larger and more blade heavy the knife, the directly greater the pressures that can be induced.
As for the Swamp Rat edge being thicker, than makes no difference unless the damage is extended beyond the edge which it isn't. You would compare the thickness of the edge that had been damaged, not the thickness behind the edge bevel. Unless the knives are similar in weight and balance, the results will be effected with the heaver and blade balanced knife taking greater stress. So scale the results if you want to compare the steels. If you just want to compare the knives you can of course just look at the raw results.
The knife was not thrown out after the chopping, it was just resharpened. Net effect was significant metal loss, but no gross damage induced. You would be looking at hours of hand honing to remove the damage.
-Cliff
Inclusions, such as the nails are far worse. The concrete is made up out of sand, cement and rocks. The sand and cement are not hard enough to damage a knife beyond blunting (damage you can't see side on at arms length). What does the damage in the concrete blocks are the rocks which are essentially inclusions in the much softer concrete. The surrounding sand and cement lessen the damage as compared to just chopping the rocks or other inclusions alone. Here are a few shots of the CU/7 to illustrate :
http://www.physics.mun.ca/~sstamp/images/cu7_concrete.jpg
http://www.physics.mun.ca/~sstamp/images/cu7_nail.jpg
The first shows the damage from 150 concrete chops (middle part of blade), and 15 nail hits (3.5" common nail, drove half way into a 4x4 and chopped into - straight down until the nails bent over or broke out). The blade was not recurved before the chopping, this is metal loss. The second shot is a blow up of the nail hits showing how they broke out sections of the edge with each conteact, fracture, not deformation. The concrete block chops did a lot of impacting as the pressure was reduced by a factor of about 10 over the nail contacts (length of contact region).
Damage will indeed be induced later on due to stresses in the blade, however these will be greater for the nail impacts due to the much higher pressures induced, same goes for inclusions in general, assuming a similar number of chops for each one of course. The concrete block chop can as well of course be compared directly to impacts right off of concrete, rocks, or other large objects accidently chopped into while clearing heavy cover. As well as having to cut through very dirty materials or metals in extreme cases, simply concrete covered wood or similar. It can also just be used to directly compare issues such as impaction resistance, ductility and impact toughness from blade to blade, or steel to steel.
Details :
The nail impacts and the concrete damage was limited to steel under 0.025" thick. I regound the edge with a steeper bevel (18 degrees per side), and repeated the cutting. Again the edge behaved in a similar manner, damage was limited to steel less than 0.025" thick. With the more obtuse angle, this of course restricted the damage depth. The chops were done at full force, the blocks were shattering upon impact one out of every 4-5 hits. If you want to compare this to the Swamp Rat pictures, note that the larger and more blade heavy the knife, the directly greater the pressures that can be induced.
As for the Swamp Rat edge being thicker, than makes no difference unless the damage is extended beyond the edge which it isn't. You would compare the thickness of the edge that had been damaged, not the thickness behind the edge bevel. Unless the knives are similar in weight and balance, the results will be effected with the heaver and blade balanced knife taking greater stress. So scale the results if you want to compare the steels. If you just want to compare the knives you can of course just look at the raw results.
The knife was not thrown out after the chopping, it was just resharpened. Net effect was significant metal loss, but no gross damage induced. You would be looking at hours of hand honing to remove the damage.
-Cliff