Tip penetration : amusing, actually quantitative as well

[Blop]

I come along with these tests as long as the describtion shows a picture / imagination, what has happend.

Exept these Dozier Agent test there wasn´t much surprising in the results.

I confess i don´t read the cutting ability comparisions because i simply don´t understand what they shall tell me and based on what.

But, their is someone with a specific knife and does something with some fotos. That truly is an impression. Better than none.

I always think: what would i do?

This is, why i don´t take the test that much serious, much more amusing and like ok, do this at home when tv is so boring.

There is no need to build up a bambus or whatever puppet for a western world knife knut. Have you ever try to stabb a standing plastic bottle? It will pop of most of the times. That test really is funny and proofs nothing more, than a finer tip will be more sucsessfull than a tactical thick one.


"People just read the results" Yes they do. And decisions, much more important than "what knife shall i buy today" are based on that.

But Cliffs tests are better than none. Better than just the advertising from any manufacturer. As i think back on that never ending thread, my last thought was: "All those who blamed Cliff for not being scientific, especially makers, should start to proof the performance of their knifes open for anyone at a level of science they have demanded." In that case Clif can reset.

Sometimes Cliffs tests are nothing more than provoking, based on the simply question: "If i buy that expensive knife, what more performance will i get, that other cheaper knife don´t deliver?"

As long as i consume knifes i read and like his tests and just compare them to me and what i would do and take them as am impression not the last word spoken.

 

[Chiro75]

But Cliffs tests are better than none.

Yes and no. Do his results represent something about the knife's performance, or about his skill level at performing a task?

This isn't about whether some review is better than no review. It is a criticism of methods involved in what is being passed off as "scientific" or "quantitative" testing, but are actually very subjective. I can't say honestly whether Cliff's reviews affect knife sales, but when it comes to a small-time custom maker, I'll bet they do.

I used to do a fair number of reviews and I know for sure that people like Sean Perkins, Allen Blade, Running Dog and some others made significant sales based upon my reviews. So, I think when someone evaluates a knife, they need to take that into consideration. Scientific analysis and backyard screwing around, no matter how precise the operator claims to be, are two totally and fundamentally different things.

This type of testing is extremely subjective, yet it puts forth as if it is extremely scientific because words like "quantitative" and all sorts of standard deviations and that little ± symbol, etc are used. In reality, these reviews affect sales and I don't believe they are being done in such a way that conclusions of the type given are fair.

In this example only, take away everything about the experiment. Let's say Cliff is the King of All Bottle Stabbers and he has perfect foot position, joint position, bottle position, perfect angulation etc etc every single time. That still leaves acceleration, and the fact that F = MA. On the first test will his acceleration be the same as on the tenth try, and will be the same on the 100th try? I doubt it. Even though Cliff "calibrates" himself somehow, there is still no control over any of the important factors dealing with this test.

The argument was that these factors don't really matter, but if factors like acceleration, angle of stabbing, etc don't matter, then how are we supposed to believe that minute things like ±3° of edge angle really matter? I have trouble understanding how the same person can claim that the movements they're making during a test are inconsequential, but that minute differences in the knife are what affects performance. I think the skill/operator makes a pretty big difference, probably more than some of the knife construction details, actually. You just have to be careful what you claim.

 

[Cliff Stamp]

My contention is that biomechanically your testing will be a bit different each sample. Different enough that no conclusions can be drawn.

Depends on how different the points are, as noted I have not stated the tolerance yet. The only way you could make such an arguement would be to take two rankings and a statement from me that this showed superior performance and THEN you could argue that the results are not repeatible to the precision I stated.

For example, lets get specific. Do you really think that I can't use this to show the WB has less penetration power than the Spyderco Military? I am confident that I can, and more so than any normal personal without a gross physical ability would make such a point obvious.

Now I am not arging this is the limit of the work, but if the above does hold then it is obviously quantitative and repeatible, to within a fairly gross tolerance of course as the points on those knives are really different, many times over soft body penetration ability for the Military.

By about 10% in the above I didn't mean from one movement from the next, I mean from one sample to the next. The only way this would not be possible would be if you think the population was highly non-normal with really huge spikes. I don't think this describes a physically healthy person.

I'm telling you that you can't repeat movements like that over and over in a way that you can draw conclusions in a test that has the method you described.

Here is what you are arguing, that it isn't possible to tell if two knives tips are significantly different in penetration power by having someone stab something. Just think about this for a few minutes before you fire off a responce and really consider what you are arguing. Think carefully what significant actually means in this case. This is the point you are missing, the level of signficance here isn't the same as in a chemical standard, it isn't even within the same order of magnitude.

I agree, but then the test should not be declared "quantitative" because it can't be repeated from examiner to examiner.

There is an actual valid point here, it has nothing to do with the random variable you describe as again, but more with large systematic differences in people. For example my brother reacts faster than me and has better hand speed, I am certain that he could get knives to penetrate that I could not. I don't see the relative performance changing, but it could on other tests. If you read the reviews it actually notes this is a concern and specificallty the types of variances you could expect with different various abilities. It also talkes about how the reviews are to be used with this in mind.

I have seen people who can't swing their arms normally when they walk because their neurological function is all jacked up ...

Yeah, it probably isn't very quantitative for them. Blind people should find other ways as well, and people without arms would have difficultly.

How do you calibrate yourself?

Same way you calibrate anything. Do something with respect to a baseline, make appropiate corrections or repeat data if such corrections are too complicated.

For example, lets say as a standard test I was doing a hang with my body weight. I then check and find out I have lost 10 lbs, the next time I do a hang I carry a plate.

The point 90 deg side to side, the penetration angle is measured through the blade how?

Mark 1 eyeball.

A stab made by hand horizontally is not a repeatabe action.

That statement is not complete, you have not defined your tolerance. Repeatible means to within a certain variance. I have not even noted the variance yet and you disagree with it, how can you possibly reach that conclusion?

... so handle/blade length have an effect on contacting speed if everything else is constant.

Yes, I talk about grip dynamics in the section on tip penetration, grip stability and ergonomics will raise tip penetration directly by raising efficiency of force transfer.

The curved surface must be met at exactly the right point to make the penetration.

There is a large fairly uniform section in the middle of the bottle, I was using 2L.

The Japanese found out that Goza tatami mats soaked overnight in water have the same resiliance to cutting as human flesh. Combined with fresh Bamboo( to substitute bone)...

Always wanted to try that, no access to it here. Plus I try to keep my work easier for the average user to have a shot at as it makes it more meaningul as they can put in in perspective easier, so I usually look for normal veryday objects and such. Plus these are the materials obviously more likely to be used.

For example, he mentioned in this thread that his wood chopping skill has improved greatly through his repeated wood chopping over the last ten years. He also says that the results of his tests have changed because of this change in skill. What that tells me is that his "tests" on wood chopping are not testing the knife as much as they are testing his skill level at chopping wood.

How can you reach this conclusion without even asking me how much they have changed? By the way it isn't that significant. I might be able to work with a knife say 10% thinner at the edge now than I could a few years ago. I try thinner blades from time to time and unfortunately I can't get past 0.025 for a heavy chopping blade.

But anyway as noted I use baselines to remove such effects, so instead of comparing how a knife fares after 4 hours of chopping now to another one three years ago, both are compared to the same blade in both cases. It is actually always the same blade for wood work, the GB Wildlife hatchet, with a Tramontina Bolo for limbing.

-Cliff

 

[Dalko]

Whether Cliff's tests demonstrate his skills at doing knife tasks or the actual knives performances, they do show that S30V, ATS-34, O1, A2 etc... even 3V chip and some of them experience catastrophic failure, where as INFI stands up with flying color.

And that clearly shows that steel companies haven't done their homework yet as far as knife steel.

 

[tknife]

Whether Cliff's tests demonstrate his skills at doing knife tasks or the actual knives performances, they do show that S30V, ATS-34, O1, A2 etc... even 3V chip and some of them experience catastrophic failure, where as INFI stands up with flying color.

And that clearly shows that steel companies haven't done their homework yet as far as knife steel.

That's a very interesting statement. So all steel makers, knife makers, manufacturers etc, except for Busse have been doing it wrong for all these dacades?

 

[Dalko]

That's a very interesting statement. So all steel makers, knife makers, manufacturers etc, except for Busse have been doing it wrong for all these dacades?

They have not been doing it wrong, but not as good as technology allows it, Busse has proven it with a steel that is very tough AND highly wear resistant AND quite corrosion resistant.

 

[conan]

Whether Cliff's tests demonstrate his skills at doing knife tasks or the actual knives performances, they do show that S30V, ATS-34, O1, A2 etc... even 3V chip and some of them experience catastrophic failure, where as INFI stands up with flying color.

And that clearly shows that steel companies haven't done their homework yet as far as knife steel.

What a crock ! INFI, being a modified A-8 tool steel was developed by some steel company ? Also, you think Dalko could get his nose any farther up Cliffs' butt ?

 

[silenthunterstudios]

Cliff, when I first came here, waaaaay back in February , I was in awe of your tests. Now, in mid April, not even three months later, I have seen the light. Why put a knife through these tests when it will not be used like that by the average knife nut user? Is it just for fun, because if it is, then great, have fun destroying these knives for no purpose other than to destroy them. But to say a knife is of poor design etc just because it does not slice cinderblocks like cheese is beyond me? Also, if you have all of this time to perform these tests, what is stopping you from posting pics or movies? I'm sure KV Collucci or another one of the mods would help you post pics etc.

 

[Chiro75]

For example, lets get specific. Do you really think that I can't use this to show the WB has less penetration power than the Spyderco Military?

That's right.

Here is what you are arguing, that it isn't possible to tell if two knives tips are significantly different in penetration power by having someone stab something.

Incorrect. I am arguing that you cannot claim that a test is quantitatively "proving" something without any control over the variables being tested.

Yeah, it probably isn't very quantitative for them. Blind people should find other ways as well, and people without arms would have difficultly.

So, in your reviews, do you specify who the results of your tests apply to?

Same way you calibrate anything. Do something with respect to a baseline, make appropiate corrections or repeat data if such corrections are too complicated.

So, in this specific test, explain step-by-step how you calibrate yourself, please. I know how you calibrate, say, a scale, but how does a person calibrate themself when performing a complex action involving a relatively high level of movement that requires a good amount of hand/eye coordination, proprioception, constant acceleration of a handheld object, etc?

I then check and find out I have lost 10 lbs, the next time I do a hang I carry a plate.

But that's not the argument. You're claiming that the variance in your motions don't affect the results of this test. That is simple, this test is not.

Again, the average reader zooms to the conclusion which states "this knife is better than that knife" and they buy it, hook, line and sinker. Again, Cliff, I will ask the question: how can you conclude that the design of Knife A is superior to the design of Knife B, based on relatively minute differences in design parameters, yet at the same time state that the variables involved in the test don't really matter?

 

[Chiro75]

That's a very interesting statement. So all steel makers, knife makers, manufacturers etc, except for Busse have been doing it wrong for all these dacades?

Correct. The tests done on this forum have quantified these facts quite conclusively. We've seen that the method the tests are being done in, according to their descriptions, is inconsequential to the tests results, and we've also seen that controlling the variables being tested doesn't need to happen to the stated variances of tolerance, so your conclusion is correct.

 

[Cliff Stamp]

I confess i don´t read the cutting ability comparisions because i simply don´t understand what they shall tell me and based on what.

They have problems indeed, do you have any suggestions on how to improve them, or additions that would make them more informative?

INFI, being a modified A-8 tool steel ...

INFI has been tested and reported here years ago, it isn't modified A8 anymore than A8 is modified S30V. Jerry Hossom who started this rumor retracted it some time ago, nice to see you keep spreading it.

But to say a knife is of poor design etc just because it does not slice cinderblocks like cheese is beyond me?

Out of the almost 200 reviews, how many of them make this statement? How many actually do any cinder block work? Do you know why it was started, I'll give you a hint, a maker asked me to do it.

Also, if you have all of this time to perform these tests, what is stopping you from posting pics or movies?

Movies I have planned for some time, not for the reasons given in the above but for others, mainly to clarify method, and get feedback on such. They should not convince you of anything though, for fairly obvious reasons.

-Cliff

 

[Dalko]

Jerry Hossom who started this rumor retracted it some time ago, -Cliff

Well Cliff, it must be very recent because just couple months ago Hossom was still spreading the rumor on KF, remember? You even took part of the discussion.

 

[Cliff Stamp]

[a average user will see no signifcant difference in how a Strider WB and Spyderco Military will penetrate a 2L pop bottle]

That's right.

Ok, now as a follow up, do you agree that the Spyderco Military has *MUCH* better soft peneration ability than the Strider WB.

So, in your reviews, do you specify who the results of your tests apply to?

Here is a something to consider, read them before debating them.

.. how does a person calibrate themself

It doesn't matter what you are doing, all calibrations are the same. You have some standard, you do something and compare to the standard.

In this case you pick a knife to use as your reference, something that you are not going to alter with extensive work. Now you periodically do long sample trials of this with what ever you are using as your test method, in this case you stab the bottle.

As it is a standard you want a high degree of precision than your measurements, usually another decimal place, so you do a lot of trials to define the standard. Now you check these points to see if there is systematic deviation which needs to be corrected.

But that's not the argument. You're claiming that the variance in your motions don't affect the results of this test.

No, I stated that you can bound the human effect to such an extent that you can draw meaningful conclusions. This is person dependent of course, my brother trains and teaches in several martial arts, he would be able to to this much more repeatible than me and thus be able to rank knives as superior which I would not be able to say are significantly different. Similar for example I do more chopping than him and thus his chopping grades are a lot coarser than mine, plus he really doesn't care that much either about that.

the average reader zooms to the conclusion which states "this knife is better than that knife" and they buy it, hook, line and sinker.

Not if they actually read the reviews. It says things constantly like this particular work is subject to personal variation, I talk about specifically how and what would be see, and do on. It actually states clearly that they are not intended to grade or pass/fail knives and that such a decision is dependent on what the users wants so make sure to consider if the work done is actually relevant to you. In fact on the forums I have stated that that I don't want the reviews to be used in this manner which is why I have avoided things like simple gradings at the end of the review which people have requested - as this would tend to make people skip the details and just jump to conclusions.

...how can you conclude that the design of Knife A is superior to the design of Knife B, based on relatively minute differences in design parameters

That is a powerful statement, I would not conclude it based on the work done in the above. What I would say is that a knife which performed significantly higher in such work, along with the phonebook work, wood stabbing and so on (general EDC work), is one which would be preferred for high penetration abilities in a knife. Thus you would want the Manix vs the Chinook for example for fine tip work and ease of penetration on soft objects, and of course by converse with different tests want a Chinook vs a Manix for strength.

...yet at the same time state that the variables involved in the test don't really matter?

Never said that, just that you can reduce their significance to the point where they can don't overwhem the tests.

-Cliff

 

[Yojimbo-girl]

Dear Cliff, and dear Chiro75, having endleslly discussions about wether Cliff's testing is scientifically sound is and will be always a a point of discussion. I don't know why everyone gets upset by the fact that a knife from brand A does something better then brand B. People who like brand A will always think that Cliff didn't took brand A to it's full potential, and Visa Versa.

I don't know why we keep seeing the same discussion about the validity of testing of the blades by Cliff over and over again! Cold Steel has been testing their knives for years, INO a very dubious way.

There is no real purpose in these tests, unless the reader has a love or hate for that specific knife.

For me these tests are just fun, and interresting to see how a blade performs under extreme conditions, but it doens't affect me in my choice of a blade.

HANG LOOSE, it's just a sharpened piece of metal!

 

[Arthur Washburn]

Cliff where are your responses to R.W. Clarks inquiries? Inquiring minds want to know.

Cliff your tests are worthless without documentation to back them up. I’m sure your years of knifemaking have made you an expert on these sorts of tests but without evidence to support your claims you are just pissing in the wind.

 

[Cliff Stamp]

Well Cliff, it must be very recent because just couple months ago Hossom was still spreading the rumor on KF, remember? You even took part of the discussion.

Yes that was exactly when he retracted it. The think that I always find illogical about such attacks is that they make no sense. Ok lets assume that Busse does make his knives out of low grade chinese bumper steel.

Doesn't this mean that it should be relatively trivial for any custom maker to make a knife which should not only duplicate the tests he does live but vastly outperform them. And if his steel is so cheap, they should be able to offer their knives for much less.

How come no one is doing it?

-Cliff

 

[NickWheeler]

First of all, posting images is not a big deal AT ALL. Even if you aren't a physicist, then going here-

http://www.imageshack.ws/

and uploading digital images is a snap.

After you upload them, then come back here and use tags to direct link to them.

I'd rather see video, as it's pretty easy to "set up" photos... but at least photos would be a start.

And as far as this thread itself-

I don't think there's anyone so stupid that they can't realize stabbing a bottle will give you SOME idea of which knife worked better for YOU.

The PROBLEM with this, or ANY of your OTHER tests, is that you try to make them sound so damn scientific... but the main body of the test is one that cannot be done with absolute repeatability and consistancy.

If you want to stab bottles and say a fine point penetrates better than a thick one, fine.

But don't come in here and tell everybody how thorough your "findings" are and drop a bunch of $20 words in the post to make it sound more substantial.

I don't have anything against you personally Cliff, I don't know you from Adam...

But what I've said here is fare regarding your posts about your "testing."

-Nick-

 

[Chiro75]

[a average user will see no signifcant difference in how a Strider WB and Spyderco Military will penetrate a 2L pop bottle]

I didn't make that assertion, for the record.

Ok, now as a follow up, do you agree that the Spyderco Military has *MUCH* better soft peneration ability than the Strider WB.

No. I don't own a WB, so I have no firsthand knowledge of it. If you showed me a controlled experiment that concluded this and the method was sensible, then I would agree. Until then, I have no idea which knife has better "soft penetration." I also don't know what your definition of "soft penetration" is.

Here is a something to consider, read them before debating them.

I have. I don't recall you ever qualifying the results of your tests like "in the hand of an experienced user, the difference is negligible" or "this makes a much bigger difference if you aren't used to chopping lots and lots of wood", anything along those lines. You take your personal experience with a knife or set of knives and extend it to conclusively apply to others and that is false reasoning. When Fred Perrin says "this balisong flips like a dream" you have to take into account his level of performance with that type of knife. Same goes for your tests, in my opinion.

It doesn't matter what you are doing, all calibrations are the same. You have some standard, you do something and compare to the standard.

It does matter! You make "calibrating" yourself sound like you twist a little dial and voila! It isn't that simple when it comes to the human body.

This is person dependent of course, my brother trains and teaches in several martial arts, he would be able to to this much more repeatible than me and thus be able to rank knives as superior which I would not be able to say are significantly different.

So, if these things you are measuring are so person-dependent, what is the point to doing them and making conclusions about them? You're measuring your ability just as much as you are measuring the differences in the knives. What your conclusion should say is something along the lines of "Based on my subjective findings, I feel like such-and-such knife did this or that better than... Your findings may be different depending on your level of skill..." Rather than "knife A is superior than knife B because I conclusively proved it..." Unless you control the human element you haven't proven anything beyond subjective. The reason experiments that have to meet base criteria for publication are controlled is for this very reason: so that conclusions CAN be made, and some level of certainty CAN be put forth. It also limits operator/examiner bias.

It says things constantly like this particular work is subject to personal variation,

Then what's the point of the review in the first place if there is that much subjectivity? The reality of the matter is that the average reader of your reviews probably doesn't:
1) Read the full review or
2) Get past the results that you encapsulate in a couple of paragraphs in what you post on Bladeforums, versus the many pages of material on your site.

I realize that's not your fault, but that's the reality, and I think you don't take that into consideration when you post your results without all these qualifying statements unless the reader link to and read the entire review.

Never said that, just that you can reduce their significance to the point where they can don't overwhem the tests.

And, again, this is what I disagree with. If you would do a controlled experiment on a knife, we wouldn't be having this back and forth dialogue. Can you imagine what would happen if safety boards "concluded" things based on tests with this much subjectivity? Thank goodness they don't!
I mean, according to what your saying, the conclusions of your tests ought to read "Based on the subjectivity of the tests performed herein, no meaningful conclusion can be made because none of the variables being tested were isolated, nor were specific variables tested against controls."

Saying you calibrate yourself against benchmarks you've made for yourself is hardly a control of variables, Cliff. Point me toward one source of information of this type where controls are not made. Your reviews read like science, but I've never seen anything like that in any scientific journal I've ever read, unless it's an anecdotal case study and everyone knows anecdotal case studies don't apply across the board. If we had a peer-review board read through reviews before they could get posted, I don't think any of your stuff would make it through with the conclusions you make.

 

[NickWheeler]

HANG LOOSE, it's just a sharpened piece of metal!

Um, yea... that many folks here produce to make a living. i.e. pay their electric bill, put food in front of their family, clothes on their kids...

But yea, they are just sharpened pieces of metal.

-Nick-

 

[Cliff Stamp]

Prime example. He claimed Strider would not stand behind their warrentee. When all the facts of the matter came into light the truth was that Strider did stand behind their products and Cliff had never even bothered to try to replace the knife. He just decided to make the claim that they would not replace the knife.

No, re-read them. The stated that they would replace the knife, it would be marked and the warrenty voided. This was in responce to someone arguing that Strider had a similar warrenty as Busse. They clearly don't because Busse doesn't promote use and then void warrenties on knives when it is repeated and the knives fail and attack a customer after asking them to review a knife. Ref :

http://www.bladeforums.com/forums/showthread.php?t=328643

He claimed then that he would send a "proof" video.

To the owner who got one. I told you I could video tape what I did when you contended parts of what I was saying and you not only did not want to see it but instead just went on a personal attack rant. These are all visible on the thread here.

Hey Cliff, what did Crucible staff/metallurgists answer you about ...

We disagreed on many things, for example in Reeves case that the drop in hardness wasn't an issue with edge retention or durability for rolling, that the splitting toughess statistic they use is relevant for what they promote it (I would argue ductility is more important for joint prying for example), plus on lots of other topics, such as use of high hardness CPM rex steels. They are pretty easy to talk to, just drop them an email. These are not uniformly accepted viewpoint, lots of people agree with Crucible, Reeve obvious for example plus the list of makers Clark mentioned earlier.

-Cliff