DOES taking a blade to Destruction PROVE anything??

I think there is a basic misunderstanding.... Some people say they don't care whether a Busse or a Trailmaster or an ATAK is tougher because they don't use knives that hard -- that makes sense, many people don't -- but those people should not be looking at those knives in the first place. If you learn nothing else from toughness tests learn that for your purposes you don't want to compromise other qualities for the sake of toughness and you're not interested in that kind of knife -- then you can go look at reviews of the kind of knife that suits your needs.

-Cougar Allen :{)
 
I just proves that anything can be broken, but I already knew that.

My father always told me use the right tool for the job; he was a man who used tools to make a living.

There's always an exception to the rule, but for the most part I think destructive testing has little real world use.


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LD
"Every Dog Has His Day"
BFC Member Since October 2, 1998

 
While a very crude destruction test only proves that anything can be broken, a well designed destructive test shows where a tool will start to be damaged. If your destructive test was the application of a pound of TNT you wouldn't learn anything. If your destructive test involved progressively applying weight to a knife stuck in a log you would learn what amount of prying was acceptable with the blade.

If you plan on depending on a knife to perform a function in the field, say cutting bone or chopping kindling, you may want to test that function (plus some margin) before you get into the field. You may not need to increase your test to the point of failure to be useful, but your test may surprise you and be destructive. If I went to the field with a skinning axe to quarter my elk and it broke when I used it I would be in big trouble. That elk is likely to be 500 pounds and too heavy to transport.

Sometimes you gotta know.
 
Most serious knife users said that they never use their knives at the limit. How would you know where the limit is without testing? If your life depends on the knife you carry (e.g. survival knives), do you not want to know if the knife is up to the task?

I was in Amsterdam in the past few days. My wife packed my suit case and forgot to give me the key. I had a SAK Handyman, and a Timberline large drop point folder in my brief case. I broke every blade in the SAK and the Timberline trying to pry open my suit case. The lug wrench in my rental car is not a pry bar type. I ended up dropping my suitcase from the third story of the parking ramp to get it open. The suitcase broke open and outcame the Busse Basic 9 among other things. Isn't it ironic?
 
Gee, NamViet Vo, wouldn't a locksmith have been cheaper?
smile.gif
 
You know there's a right tool for everything, in this case it was probably a paper clip.

I had a case where some tools were locked in a small metal tool box. I recognized the type of cheap padlock so I asked for a small hammer. The technician came back with a medium claw hammer. I explained that I wanted a small ballpeen hammer with the head around the weight of the padlock. He looked confused, but found me something smaller. I showed him how to rap open the lock by tapping sharply on the side of the lock body and having the body move faster than the spring loaded locking bar. The lock popped open without so much as a dent. He thought I was going to try and pound open the box.
 
I was staying in Zoetermeer, it was 10:00 p.m. Sunday night, and the cheapest way was to buy a new suit case. Paper clip was not even a reasonable option with the lock that I got.
 
VERY interesting topic.

First thing I would like to do is replace “destruction” by “failure”. Your intention shouldn’t be to bring the product you are testing to destruction but to failure. The difference is that destruction has nothing to do with intended use of the product, while failure is the limit where the product is not longer able to fulfill the required task. Those failure tests can show exactly where the limits of the tested products are.

Back to the car example: If a crash test simulates a real world scenario like side or front impact accidents, then you can easily predict how other cars of the same type would behave in such an accident. By relating speed to the likelihood of which passenger will survive the accident, you can also evaluate different types of cars in terms of safety. On the other hand if you would run over a car with a tank, the result won’t be too useful, simply because the situation is very unlikely to occur and nobody would care about the outcome.

Same with knife testing. If you do the rope cutting test until the edge of the knife fails (you destroyed the edge), it will exactly tell you how many cuts you can make. Those results can be used to evaluate the edge holding of different blades. If you on the other hand you cut the blade in half with a torch, it doesn’t proof much except that metal will melt when subject to high temperatures. And to proof that you don’t need to use a knife blade.

Now let’s take a look at the bending tests. Putting a blade in a vice doesn’t make much sense at first, but if you think that a big knife will be used for prying, then this test can tell you how much torque the blade can take until it fails. Again, if you apply numbers to those findings, you’ll be able to compare different brands.
 
As for KBARs, I have broken nearly ten of them, and not intentionally either. At their price point they perform well.

Anyway, as for destructive testing, it lets you know the limits of your eqiupment. I do a fair amount of climbing, and really appreciate the fact that every piece of hardware was at some point taken to failure. Testing is an integral part of any design process, and most of it is done to the point of failure. And what is gained? DATA. This should speak for itself.

As for the tool issue, sure every care should be taken to use the right tool, but when I am out back packing, or was in the field with a light unit one doesn't carry the craftsmen tool set. I have needed and used a sharpened pry bar more times that I can count. HUMVEE trailer hitches always seem to get jammed. Personally want a knife that can chop, pry, puncture, and cut.

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"Women bring life into the world
and much death, for they sway the
destinies of men." -Anneas
 
I consider my knives to be important safety equipment. In my industry, all safety equipment is tested to the point of failure in order to rate it for varios uses. This allows you to choose the correct equipment for the job.

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James Segura
San Francisco, CA


 
It proves at least one thing, it gets people talking about it.

You can say anything you want about me, just spell my name right.
 
Hello,

Another interesting idea would be , in an above post if Taking a blade to Failure where it doent perform what its designed to do.

I mean every time a Blade became dull and wouldnt cut would constitute Failure,, that not in itself would relate to Performance equalling the COST/Performance Ratio.


Great posts, Take Care,

Allen blade

[This message has been edited by Allen Blade (edited 10 December 1999).]
 
Just to expand to what Cougar noted, strength and toughness are integral to all aspects of knife usage for all types of knives. If a maker tells you "it doesn't need to be" or "that's not important" in respond to you asking about the strength/durability of a blade, then either (a) they are intentionally trying to decieve you which is pretty bad or (b) they actually don't know any better which is probably worse.

As an example, I currently use as my light utility knife a CPM-10V blade which is uniformly hardened to 62.5 RC. The stock is 1/8", and the blade has a full flat grind with a distil taper. The edge is .01" behind the bevel which is ground less than 15 degrees. The only reason this knife is usable in this geometry is that it has the strength to hold the edge that thin and the toughness to prevent chipping. I switched to this blade from a D2 one (similar geometry) as the CPM-10V blade cut better because it was thinner and yet still resisted damage more (edge rolling, wear and chipping).

If there was a material out there that was directly stronger, tougher, and more wear resistant than CPM-10V I would call up Phil Wilson and ask him to grind me a blade out of it using even thinner stock and make it even harder. I would then have a much better cutting tool that had a wider range of applications, ie. a better knife.

-Cliff

[This message has been edited by Cliff Stamp (edited 10 December 1999).]
 
Cliff is right; it's useful, even vital, to know what any kind of knife can take, even pen-knives ... the pen-knife fans know they can't do pullups on their knives but they'd like to know whether they can apply ten pounds of prying force to it without hurting it ... if they knew they could, those guys who say "I never pry with a knife" would start doing it, and find it very useful....

Namviet Vo's suitcase test would have been more useful if he had tried dropping it from progressively greater heights until he found the point of failure ... as it is all we know is with that amount of weight in it, it couldn't take a 3-story drop -- but could it have taken a 2-story drop without damage? Of course we can understand why he didn't conduct exhaustive testing under the circumstances, but next time one of gets an opportunity like that let's try to be a little more rigorous, huh?
smile.gif


-Cougar Allen :{)
 
Ralf, Steve, Et Al.

It's called 'destructive testing' because that's what the materials science folks call it, and to distinguish it from nondestructive testing (NDT). NDT can give you good information, but for my money, systems must be tested to failure in order to set the end point of the graph. NDT is useful in that it allows you to predict behavior before failure, but only after establishing where the failure point is.

Maybe this is nitPicking, but it's important for tool users to understand what's being discussed here so that they can read specs and makers' claims with a properly functioning BS meter.

db
 
Our company fills dumpster after dumpster with products that have been zapped with power line variation, zapped with ESD, 'shaked and baked' wet and dry, frozen, dropped, dropped in the package, used to failure, etc., as it's one of the few reliable ways to determine performance margin.
 
I have an idea!! I'll build a knife cannon that we can load a knife into and blast it into a wall of 2 by 4s. That way we can find out what effect, impacting a wall of wood at supersonic speeds will do to a knife. Whatcha think?????????

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"Always think of your fellow knife makers as partners in the search for the perfect blade, not as people trying to compete with you and your work!"


[This message has been edited by L6STEEL (edited 11 December 1999).]
 
L6- sounds like a party. Let me know if you survive the event.

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James Segura
San Francisco, CA


 
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