Knifetests.com Project 1 Destruction Test.

hlee said:
From the possum...

"The specs say it's A2 at 55-57 RC. Take a look at this spec sheet for A2: latrobe steel A2

Anyone else notice what happens to the toughness curve right as the hardness curve crosses 55 Rc?"

If I am reading the chart correctly, as the hardness drops below 55, the toughness goes up. Should this surpirse anyone? In other words, there is a minimum toughness "trough" at around 55 HRC. However, look at the toughness curve in the range where HRC is 57-59. There is a peak in toughness (~145 ft/lb) at HRC 57-59 (tempering temperature of 316C). So, according to latrobe, if CRK is doing the heat treat correctly, maximum toughness should be attained at the HRC they are running their blades. Should this surpirse anyone?
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Ok you have convinced me. It must be a design issue.
 
hlee said:
However, look at the toughness curve in the range where HRC is 57-59. There is a peak in toughness (~145 ft/lb) at HRC 57-59 (tempering temperature of 316C). So, according to latrobe, if CRK is doing the heat treat correctly, maximum toughness should be attained at the HRC they are running their blades. Should this surpirse anyone?
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I'm not sure if I am understanding you correctly, but, I would agree with you that the peak toughness according to the chart seems to be 57-59 RC with emphasis at 57 RC. However, CRK heat treats at 55-57 RC, not 57-59RC. 55 RC is where the trough lies.
 
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It’s interesting that both CRK knives broke on the serrations. I wonder if you ground the serrations completely off (essentially making a choil) if the knife would do better in the impact tests.

There’s nothing like real world tests to bring out the best (or worst) in a tool.

Nice job Noss :thumbup:
 
Sorry, Noss, but IMHO, all your tests show is that it's possible to break just about anything if you really want to. As far as identifying useful or well-made knives, nada.

After a long life, using a knife daily, I've never had to do any of the "serious" things you do to the knives.

Still, I'll bet it's great fun to play with your knives this way - hope you continue to have fun.
 
I'm not against these test, and some knives have surprised me both good and bad, but I just cannot imagine a situation in the real world that would warrant beating a knife into wood or concrete with a sledgehammer.

The earlier tests with the webbing cuts, batonning and maybe digging the point into wood are fair, but the sledgehammer just seems unrealistic.
 
JoHnYKwSt said:
I'm not sure if I am understanding you correctly, but, I would agree with you that the peak toughness according to the chart seems to be 57-59 RC with emphasis at 57 RC. However, CRK heat treats at 55-57 RC, not 57-59RC. 55 RC is where the trough lies.
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This isn't the only steel type that does this either. According to Crucible, toughness for S-7 drops significantly between 55 RC and 52 RC, so if you were going to make a knife out of it you would want it to be at 51 or below, or 56 RC, but not between those numbers (and not much higher than 56).

According to the chart from Latrobe, A-2 behaves very similarly. With toughness piquing between 57 RC and 58 RC, bottoming out around 55 RC and rising sharply from there (toughness being fully regained around 52 RC).
There's not much room for error, which is why heat treating is such a difficult thing.
People who have worked with the same steel for a long time tend to get to know it's traits better than a simple chart, so maybe Chris Reeve is simply doing what he thinks is best. That said, it would appear that he still hasn't quite got the formula quite right.
 
Grampa said:
Sorry, Noss, but IMHO, all your tests show is that it's possible to break just about anything if you really want to. As far as identifying useful or well-made knives, nada.

After a long life, using a knife daily, I've never had to do any of the "serious" things you do to the knives.

Still, I'll bet it's great fun to play with your knives this way - hope you continue to have fun.
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The Chris Reeve website says of the Green Beret.
" ... It is a no-nonsense, hardworking tool" ... "the Green Beret Knife is a using knife that, just like the men for whom it was designed, is efficient, tough and uncompromising."

Should a hardcore military knife that is "tough and uncompromising" break like candy-glass when tapped through a 2X4?
 
I loved the point in the video where he breaks the knife and he says, OH SHIT! Like he really did something wrong. LOL!
 
Grampa said:
Sorry, Noss, but IMHO, all your tests show is that it's possible to break just about anything if you really want to. As far as identifying useful or well-made knives, nada.

After a long life, using a knife daily, I've never had to do any of the "serious" things you do to the knives.

Still, I'll bet it's great fun to play with your knives this way - hope you continue to have fun.
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There's a great deal of added control I'd like to see incorporated into these comparisons before I'd call them excellent tests, however the fact that your experience has not led you to use a tool in these ways is really rather irrelevant. The knives being compared and contrasted here all share a common trait---they're marketed as "tough" knives, or "combat" knives. If your uses are neither tough nor combative, then fine, but lets explore the mindset that testing these parameters is useless.

Mattress manufacturers use giant, heavy rollers to test the life expectancy of their products. Instead of having to wait fifteen years to find out if their mattress will last fifteen years, they put it through absolute hell in the form of friction and compression, and then compare it to other mattress designs/materials that have gone through the same process. Now, you could say "I've been sleeping on beds all my life and I've never needed to run a giant roller over one!" if you wish, but I'd hope you were just being ironically argumentative instead of genuinely unable to grasp the purpose. ;)

The purpose of testing a product to its limits is to discover those limits. Bridges, chains, motors, sheets of safety glass and childrens' swingsets all go through this--being taken to the breaking point to discover what the breaking point is. It's not just to find out "can it be broken" as that's absurd--of course it can. How, when, and why it breaks are the questions, as well as whether or not it lives up to its claims.

If a new fillet knife manages to clean 10,000 fish in between sharpenings, the fact that I'm not a professional fisherman and will never need to clean 10,000 fish doesn't mean it's useless information.
 
Wow :eek:

I wasn't expecting that result.

The tests may not be scientific but make you sit up and ask questions.
 
t1mpani said:
Mattress manufacturers use giant, heavy rollers to test the life expectancy of their products. Instead of having to wait fifteen years to find out if their mattress will last fifteen years, they put it through absolute hell in the form of friction and compression, and then compare it to other mattress designs/materials that have gone through the same process. Now, you could say "I've been sleeping on beds all my life and I've never needed to run a giant roller over one!" if you wish, but I'd hope you were just being ironically argumentative instead of genuinely unable to grasp the purpose. ;)

The purpose of testing a product to its limits is to discover those limits. Bridges, chains, motors, sheets of safety glass and childrens' swingsets all go through this--being taken to the breaking point to discover what the breaking point is. It's not just to find out "can it be broken" as that's absurd--of course it can. How, when, and why it breaks are the questions, as well as whether or not it lives up to its claims.

If a new fillet knife manages to clean 10,000 fish in between sharpenings, the fact that I'm not a professional fisherman and will never need to clean 10,000 fish doesn't mean it's useless information.
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Great post!
 
t1mpani said:
There's a great deal of added control I'd like to see incorporated into these comparisons before I'd call them excellent tests, however the fact that your experience has not led you to use a tool in these ways is really rather irrelevant. The knives being compared and contrasted here all share a common trait---they're marketed as "tough" knives, or "combat" knives. If your uses are neither tough nor combative, then fine, but lets explore the mindset that testing these parameters is useless.

Mattress manufacturers use giant, heavy rollers to test the life expectancy of their products. Instead of having to wait fifteen years to find out if their mattress will last fifteen years, they put it through absolute hell in the form of friction and compression, and then compare it to other mattress designs/materials that have gone through the same process. Now, you could say "I've been sleeping on beds all my life and I've never needed to run a giant roller over one!" if you wish, but I'd hope you were just being ironically argumentative instead of genuinely unable to grasp the purpose. ;)

The purpose of testing a product to its limits is to discover those limits. Bridges, chains, motors, sheets of safety glass and childrens' swingsets all go through this--being taken to the breaking point to discover what the breaking point is. It's not just to find out "can it be broken" as that's absurd--of course it can. How, when, and why it breaks are the questions, as well as whether or not it lives up to its claims.

If a new fillet knife manages to clean 10,000 fish in between sharpenings, the fact that I'm not a professional fisherman and will never need to clean 10,000 fish doesn't mean it's useless information.
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EXACTLY!! Should make this a sticky post.
 
hlee said:
So, according to latrobe, if CRK is doing the heat treat correctly, maximum toughness should be attained at the HRC they are running their blades. Should this surpirse anyone?
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It's funny that you seem to be reading the chart correctly, but then draw the opposite conclusion. :confused:

My point is that this steel is fairly tough around 58 Rc. And it's nearly at its weakest at 55. (almost as brittle as it is as quenched with no temper whatsoever) The curve says if you want it tough, temper it to either 58, or below 52, but for heaven's sake avoid 55.

Now granted, this is just a rough guide, and I'm sure things could shift around a bit depending on a number of factors. However, it shows that this steel is unlike what we normally think of with simpler steels, in that drawing the temper down does not automatically equate to greater toughness. And considering how this blade actually behaved, I'm wondering if it is indeed right around 55Rc, and if the curve is describing what happened, perfectly.
 
t1mpani said:
If a new fillet knife manages to clean 10,000 fish in between sharpenings, the fact that I'm not a professional fisherman and will never need to clean 10,000 fish doesn't mean it's useless information.
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And that would make sense, since a fillet knife is used for filleting fish.

But Noss isn't testing for that, is he? He's just seeing what it takes to bust the knife.

If you want a "knife" to bust up concrete or get hammered on by another chunk of steel (neither of which are normal uses of knives), get one designed for the purpose. As far as I know, only one knife maker designs for that - go buy his knives, and have fun beating the heck out of them!

I stand by my opinion: Great fun to play with a knife this way, but it doesn't tell me anything about the quality or usefulness of the knife as it was designed to be used.

Testing how many fish it can fillet before it needs resharpening would. :thumbup:
 
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