Regarding IDIOT tester.

[nozh2002]

Guys,

I can not understand the critique for something we are getting for free. If PC World can destroy iphone 3g as part of their review why destroying knives should be any different? Don't like it don't watch it

http://www.pcworld.com/article/148310/its_tough_to_kill_an_apple_iphone_3g.html

Well, this is not about scientific test or not, in some cases this is outraged "proud owners" of knives which did not show real greatness in Noss's tests. It is hard to admit to yourself in the first place that you super knife is not so super, this is why emotional level is so high - raising voice human usually trys to dismiss deep internal doubts. Fear of you own failure make anybody angry.

Thanks, Vassili.

 

[markksr]

Well, this is not about scientific test or not, in some cases this is outraged "proud owners" of knives which did not show real greatness in Noss's tests. It is hard to admit to yourself in the first place that you super knife is not so super, this is why emotional level is so high - raising voice human usually trys to dismiss deep internal doubts. Fear of you own failure make anybody angry.

Thanks, Vassili.

Actually, a good bit of this is about "scientific test or not". More specifically about your incredibly ignorant assertations that Noss's tests are "scientific" even after his own admission as well as many others' explanation that they are not.

It would be nice if you would stop blaming anyone's disagreement with you on your imagined emotional shortcomings. This is nothing more than a pathetic attempt at a strawman argument.

You really just continue to sound more and more ridiculous the more you respond...

 

[nozh2002]

Someone please shoot me...

???

Thanks, Vassili.

 

[Gator97]

Darthsoaker, Gator97 is still arguing that because a human cannot replicate a machine, the tests by the machine are not scientifically valid.

I do not argue validity of the test, or math, or the fact that scientific test will provide useful data. Once again, my point is how close the machine test comes to human use. It has happened in many areas and knives are no exception when the controlled, lab test doesn't provide correct picture of the everyday use. Why is that so hard to understand or why knives would bean exception?

As a software engineer, presumably your professional life revolves around human variability. Lets face it, people do some stupid stuff with their computers

Yes, the amount of code that has to be written to prevent users from doing wrong things, validation of the input data, error handling, etc is significant. Knife makers have to do the same in certain aspects. Having lower than Max hardness is one of them. Mass knives are ground for very thick edges to protect the makers from unhappy buyers because very thin edge failed. I guess there are other tricks makers do to make their lives easier and protect themselves and users from themselves probably.

How a human abuses the knife has a direct correlation to the observed toughness in this world. The question that you ask is, can a human break this blade? If it breaks once, the answer is yes.

I don't ask if the human can break a knife. In 99.99% of the cases the answer is yes. I'm nore interested if the knife will break as a result of unintentional error, extreme use, etc.

Besides, you assume that most of the abuse to the knife is intentional or malicious. But accidents do happen, or you work with a knife long time, your hands and palms get tired, you loose control, you may miss the target and hit concrete, hit at the wrong angle, whatever else. I view what Noss is doing as some sort of approximation of that. It is not scientific, but unlike rig test it's more close to what happens in those situations.

 

[Broos]

if the machine does not induce the lateral stresses and random impacts in chopping, then it probably isn't doing a proper durability test of the knife - heat treat, steel, grind, profile. Rigid tests aren't less accurate, they're a less accurate representation of use.

I'll let Wayne Goddard and Professor Nelson address lateral forces. This thread was aboout edge retention testing and numerical analysis. These posts were in response to Cliff's assertion that machine testing is invalid due to lateral forces. Maybe you remember it?

We wouldn't get test results within 5% if we had lateral forces taking place. It’s not hard to hold the knife at 90-degrees to the cutting platform.

...

I think I know of what I write. I've been teaching my sharpening class for thirty years at knife shows, hammer-in's, and schools and on hunting trips. Most knife users don't know a wire edge from a carbide. Some get it lined up and think they have a sharp blade; however it will not have the endurance cutting ability that it will with a true sharp, wire-free edge.

Wayne G

I think Wayne and Phil are among the best at testing blades on rope by hand, but we recognized we were not. We decided to eliminate the "human" factor and went with the CATRA test.

My personal feeling is that machine testing will be representative of good human testing. There will probably be a scalar factor, but I think the trends will be the same when comparing different steels (all other factors being the same).

I think it would be interesting to do a round robin assessment of hand testing versus machine testing. My hypothesis is that the larger the number of people testing by hand, the larger the deviation will become. This isn't saying it is bad testing or data. I think I would imply that without a "standard" results will vary and discriminating between results is very difficult.

Those are my thoughts.

TN

Can someone define a knife's "toughness" for me? It has been mentioned many times, but it has never been defined once. This really should have been the first question in this discussion. It is hard to have a scientific or repeatable test when what we are trying to determine is a subjective or undefined characteristic. I suspect it would be difficult to reach a consensus on it, too.

 

[theonew]

Can someone define a knife's "toughness" for me? It has been mentioned many times, but it has never been defined once.

It's like pornography, you'll know it when you see it.

 

[Abacus]

hlee, I've really enjoyed reading your posts in this thread. Really well thought out and articulate. I followed what you were getting at and agreed 100% the whole way.

 

[hardheart]

I'll let Wayne Goddard and Professor Nelson address lateral forces. This thread was aboout edge retention testing and numerical analysis. These posts were in response to Cliff's assertion that machine testing is invalid due to lateral forces. Maybe you remember it?

Yes, but I was referring to chopping, where fatigue and misjudged distances & angles will ruin your day.

Can someone define a knife's "toughness" for me? It has been mentioned many times, but it has never been defined once. This really should have been the first question in this discussion. It is hard to have a scientific or repeatable test when what we are trying to determine is a subjective or undefined characteristic. I suspect it would be difficult to reach a consensus on it, too.

I gave up on that. I still try to use it as resistance to fracture from impacts.

 

[Rafael]

... ... ...

I view toughness as an intrinsic property of the blade. Handle material, fasteners, blade shape, profile, height, width, primary bevel angle, edge grind and angle, spine thickness, distal taper, blade steel, and heat treat all play a role. However, at its core, toughness is a property of the knife. Just like with the enzymes, human variability and test variability hide the property under study. In order to compare one knife against another, human and test variability must be removed or minimized, or the comparison is meaningless. Likewise, replicates should be done in order to assay for variability in the sample set. Was the first result an aberation? Do it again and find out.

Once is an accident. Twice is a coincidence. Three times is the beginning of a trend.

I only carry one knife at the time (actually two, knife of choice + SAK . Some knifes are promoted as tough, strong, reliable and intended for hard use by the manufacturer of that knife.

If it breaks unexpectedly when I use it, I find no solace in the fact that another knife from the same manufacturer might have performed better. Or that the knife might have hold up if I had chopped at a slightly different angle.

The testing by Noss might be informal but all his actions are recorded, so anybody can draw their own conclusions or test a similar knife in a similar way or better way.

I prefer that to a written review were somebody claims knife X is incredibly tough…

Making a record of what you do is the beginning of scientific testing.

Rafael

 

[Vorpal Blade]

I was alluding to a recent set of videos by Noss where he broke two knives by a well known maker. Some argued that it was a sampling issue ie, a bad one gets out every now and again. My question is what are the odds that two knives- different models, from the same company, bought at different times, by one person- would both be outliers of their respective populations? Others argued that it was a design issue, as both broke at the same place. However, all we really have is two broken knives, and no real quantitative data from which to draw conclusions. "Wow, that knife broke way before I thought it would" is not sufficient for comparison.

As I observed earlier, Noss' tests by themselves, are inconclusive. However, if others were to do destruction tests on knives by this "well known maker" and got a high percentage of similar failures, the validity of the tests could no longer be denied. It would become obvious that the maker in question is releasing a significantly high percentage of knives to the public which are less durable than other brands tested. This is important information for prospective buyers, especially when the maker in question claims his knives will withstand hard use.

I have not heard of many Bark Rivers, Busses or Fallknivens which turn up with bad heat treatment or structural flaws. Rigid manufacturing standards and high levels of quality control screen out most defective knives. But some brands of knives are marketed with claims their makers cannot back up. A sampling of destruction tests should put the lie to fraudulent bragging.

 

[kurodrago]

As I observed earlier, Noss' tests by themselves, are inconclusive. .

Explain to us "by example" a conclusive test!

 

[Vorpal Blade]

Explain to us "by example" a conclusive test!

If one sample of a certain model knife breaks easily in destruction testing, it is not conclusive that other samples will break just as easily. To find out if the first test result was not a fluke, other samples need to be tested in the same way. If they all break just as easily, the results become fairly conclusive that the first knife was representative of most other copies of the knife. The more knives tested, the more conclusive the results.

 

[kurodrago]

If one sample of a certain model knife breaks easily in destruction testing, it is not conclusive that other samples will break just as easily. To find out if the first test result was not a fluke, other samples need to be tested in the same way. If they all break just as easily, the results become conclusive that the first knife was representative of most other copies of the knife. The larger the test sample, the more conclusive the results.

Your talking about probability? Onehundred knives equal strength in the same text they will broken in 100 different ways! Which one is the most conclusive for you? Two knives are not conclusive as 100 knives...we are far from perfection.

 

[Vorpal Blade]

Your talking about probability? Onehundred knives equal strength in the same text they will broken in 100 different ways!

Got proof?

Which one is the most conclusive for you? Two knives are not conclusive as 100 knives...we are far from perfection.

True.

 

[hlee]

I only carry one knife at the time (actually two, knife of choice + SAK . Some knifes are promoted as tough, strong, reliable and intended for hard use by the manufacturer of that knife.

If it breaks unexpectedly when I use it, I find no solace in the fact that another knife from the same manufacturer might have performed better. Or that the knife might have hold up if I had chopped at a slightly different angle.

The testing by Noss might be informal but all his actions are recorded, so anybody can draw their own conclusions or test a similar knife in a similar way or better way.

I prefer that to a written review were somebody claims knife X is incredibly tough…

Making a record of what you do is the beginning of scientific testing.

Rafael

The only way to be sure that your knife will not break unexpectedly is to expect it to break at any time.

However, if you test 100 of knife x and 3 break and 100 of knife y and 21 break, you can be relatively certain that a random sample of knife x will be tougher than knife y.

Alternatively, if you test knife x and it breaks after 300 repetitions of a test, and knife y breaks after 600 repetitions of the test, then knife y has shown to be tougher. Of course, this would also need to be repeated so as to eliminate sample variability.

I feel that I should not have to repeat this, but all tests should be controlled such that all samples are subjected to the same (in all ways) test or the conclusions are void.

Toughness is the ability to resist breakage, chipping, cracking, etc.

Hardness is the ability to resist deformation, rolling, bending, etc.

Glass is hard but not particularly tough.

Rubber is tough but not particularly hard.

 

[knarfeng]

As I observed earlier, Noss' tests by themselves, are inconclusive. However, if others were to do destruction tests on knives by this "well known maker" and got a high percentage of similar failures, the validity of the tests could no longer be denied. It would become obvious that the maker in question is releasing a significantly high percentage of knives to the public which are less durable than other brands tested. This is important information for prospective buyers, especially when the maker in question claims his knives will withstand hard use.

Oh PLEASE. All it would show is that if you beat the crap out of a knife long enough it will break.

 

[shecky]

It seems Noss' detractors take some solace in the notion that his tests are not scientific. It would be mistaken, however, to conclude that his tests are not useful.

Can someone define a knife's "toughness" for me? It has been mentioned many times, but it has never been defined once. This really should have been the first question in this discussion. It is hard to have a scientific or repeatable test when what we are trying to determine is a subjective or undefined characteristic. I suspect it would be difficult to reach a consensus on it, too.

"Toughness" seems to be a term that used with more precision by metallurgists and knife manufacturers than by knife nuts. The former uses the term to mean the ability of a particular steel to resist to shock and impact.

 

[Vorpal Blade]

Oh PLEASE. All it would show is that if you beat the crap out of a knife long enough it will break.

Can't deny that. The main point of destruction testing is to find out exactly when a knife quits while it's getting the crap beat out of it. Some last a lot longer than others.

 

[Vorpal Blade]

The only way to be sure that your knife will not break unexpectedly is to expect it to break at any time.

However, if you test 100 of knife x and 3 break and 100 of knife y and 21 break, you can be relatively certain that a random sample of knife x will be tougher than knife y.

Alternatively, if you test knife x and it breaks after 300 repetitions of a test, and knife y breaks after 600 repetitions of the test, then knife y has shown to be tougher. Of course, this would also need to be repeated so as to eliminate sample variability.

Toughness is the ability to resist breakage, chipping, cracking, etc.

Hardness is the ability to resist deformation, rolling, bending, etc.

Glass is hard but not particularly tough.

Rubber is tough but not particularly hard.

I agree with this in every detail.

I feel that I should not have to repeat this, but all tests should be controlled such that all samples are subjected to the same (in all ways) test or the conclusions are void.

Here's where we part company. For precise measurement of when failure occurs, it would be desirable to subject all samples to exactly the same stress. But even with somewhat variable testing, large differences in performance can still be discerned. Repeatability of results lead to meaningful comparisons.

 

[hlee]

Repeat after me...

"Repeatable results come from controlled tests."