Steel Edge Retention testing

You all have engineer mentality! It will not be possible to eliminate random nature of this business. Only way to do this statistic. You may spend years to eliminate variation in thread tension to find out that there is some other parameter you did not notice.

It is like perpetual machine - engineers may spend years to invent different constructions, while it is impossible because of fundamental law of physics. Just because they have too narrow focus.

In result nothing will be ever tested, as it was before.

Instead we may have more or less stable results which can more or less describe steel properties.

Thanks, Vassili.
 
nozh2002 said:
You all have engineer mentality!
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Surprise! I've worked as an engineer for a number of years and I agree with you: in designing tests statistics are a very important tool for mitigating the impact of random variables related to technique. The trick is to eliminate fixed variables (such as edge thickness) through method and you have obviously worked hard to do this.

It should be noted that even the most rigid, well designed mechanical testing kit would require statistics to even out variations since the edge changes seen, especially when the knives are sharp, would almost certainly be smaller than the machine tolerances. Even if they weren't I would have trouble trusting a single test result taken in isolation and I have, professionally, seen real problems arise when people do.

Watching your results with great interest!
 
Thank you. You do explain this best.

I always pick irritative way to express my point. Sorry.

Thanks, Vassili.
 
Looking over the results again so far and thinking about all the variables it seems to me that for a few hundred cuts all of these steels seem basically comparable. 10 or 20 grams here or there is essentially meaningless to the end-user and probably well within the margin of error. The only concrete result seems to be that 420HC died a premature death. I think it would be more meaningful to see the point at which each of these steels fades quickly away and that might mean several thousand cuts of manila rope. Yikes.
 
theonew said:
Looking over the results again so far and thinking about all the variables it seems to me that for a few hundred cuts all of these steels seem basically comparable. 10 or 20 grams here or there is essentially meaningless to the end-user and probably well within the margin of error. The only concrete result seems to be that 420HC died a premature death. I think it would be more meaningful to see the point at which each of these steels fades quickly away and that might mean several thousand cuts of manila rope. Yikes.
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Meaning of 10-20 grams difference can not been disregarded just because this is only 10-20 grams difference. This is based on 21 cuts and not on single cut - if you do only one test and have this difference it meaningless, but here we have some distribution - not single cut.

Plus this is not only one measurement but full history of sharpness changes with 10 cuts step (first ten does not really represent too much - single cut gives ore or less random load but ten is more stable). This is also much more informative then single measurement after 100 cuts, because gives idea of how blade behave.

Thanks, Vassili.

P.S. For 800 cuts is quite a bit load - you may try yourself and see is if it reasonable load and how it may relate to practical load for regular user.
 
I agree with you both... the difference is not meaningless because of the number of cuts smoothing out results, but it is also fairly insignificant in use, imo, to have a 10-20g difference.
 
hardheart said:
I agree with you both... the difference is not meaningless because of the number of cuts smoothing out results, but it is also fairly insignificant in use, imo, to have a 10-20g difference.
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I have second part - you can not pick one or other line from the table and make judgment based on it. All data need to be considered. You may look at this from different point. But this is all numbers play no more.

Like based on first two line we may say - CPM 440V lost sharpness twice after single cut, CPM S30V lost 50% of sharpness after single cut and BG-42 keep sharpness unchanged... Or you may say it take CPM 440V to came from 20 to 70 120 cuts while for CPM S30V it is only 35 cuts and for BG42 40 cuts. Now we say like CPM 440V last longer 3 times then BG42 and even more then CPM S30V...

This is simple example - anybody may play with numbers, making them significant or not - depends on how you look at them. But you need array of numbers to start this play on the first place. Ad this is what I am doing.

Thanks Vassili.
 
understood, what I mean is that if you need to cut a bunch of rope for some activity, not measuring results, just cutting, then it doesn't appear it matters if your knife is ATS34 or S30V. Heck, 420 is just as good for a few hundred cuts.

For slicing, for cutting other materials, for impacts, etc., there are of course other things to consider. But, this one test shows to me that in this one measure, there isn't a mind-blowing difference between the premium steels. If your primary use of a knife is cutting through rope, worry more about sharpening technique than which supersteel you have. It's a bit different than the often stated 'get a D2 blade for rope cutting.'
 
hardheart said:
But, this one test shows to me that in this one measure, there isn't a mind-blowing difference between the premium steels.
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That's what I was getting at, just not so eloquently. This in itself is a rather surprising result to me at least.
 
Or yes sure difference is not too significant to be practical - but at least now you may back up this with real test data. One thing is to say - I did not see any difference and another is after cutting 1/2" rope 100 times with 8 different steel by measuring sharpness after each 10 cuts we final difference is not too significant from 60 to 90 gramms (I excluded INFI, ecause I am retesting it now and think that first run may not be too accurate)...

Thanks, Vassili.
 
I do think this test and most tests are meaningful. However, I've myself found that there is a big difference between a measurable difference, and a noticeable difference with the better heat treated steels. To be clearer I think the only way you really can tell a difference between well heat treated steels is to measure it with tests. Normal use of a knife is so varied and the performance of well made knives is so good these days it is almost impossible to notice better performance of the steel without the test. Heck even measuring wile testing is difficult to determine a clear better performance. Still tests provide alot of value and meaning, but sometimes they are given too much importance I think.
 
Manufacturers continue to use steel as an important factor in marketing claiming that this or that steel is superior to others. I think it is nice to know what is the difference for sure and have some way for everybody to check it for themselfs.

Thanks, Vassili.
 
I just did some testing because of all that I see going on here. It amazed me that steels that are considered "good" and "poor" can really be quite the opposite, depending on the use and the heat treat. In my simple rope cutting on a scale test, 420HC easily outperformed 1095, at the hardnesses and grind of the samples. I guess it really is important for the maker to know what they are trying to accomplish, in order to end up with a really good blade. You cannot just throw a steel at it, the grind, heat treat, and everything else hase to play along.
Nozh, I really like seeing the steels compared. Thanks for the effort.

P.S. Am I reading the tables correctly, that the S60 and the BG42 get extremely sharp, and seem to keep that razor edge well? Also, do you have any personal observations on the differences between cutting manilla and nylon rope? Thanks.
 
Any Cal. said:
I just did some testing because of all that I see going on here. It amazed me that steels that are considered "good" and "poor" can really be quite the opposite, depending on the use and the heat treat. In my simple rope cutting on a scale test, 420HC easily outperformed 1095, at the hardnesses and grind of the samples. I guess it really is important for the maker to know what they are trying to accomplish, in order to end up with a really good blade. You cannot just throw a steel at it, the grind, heat treat, and everything else hase to play along.
Nozh, I really like seeing the steels compared. Thanks for the effort.

P.S. Am I reading the tables correctly, that the S60 and the BG42 get extremely sharp, and seem to keep that razor edge well? Also, do you have any personal observations on the differences between cutting manilla and nylon rope? Thanks.
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Any steel get extremely sharp - in this regards my experience - there is no difference so far, it is just matter of sharpening skills. To say is it keep that "razor sharp edge" we need to define what it is - "razor sharp edge". Initial 20 grams is I think better then razor sharp. Then for example if we define it like 60 grams then we may say that fro 20g to 70g for S60V and BG42 we need 130 cuts and 40 cuts... So, I rather let everybody make their own conclusion. In general I think difference is not so big.

I talk to Russian hunter (on knife forum in Israel) - to my test on Lauri he add that he able to process entire bear with Lauri without resharpening. This is more practical and visible test with complex load of many blade properties. Of course I prefer to have statistically reliable results - Like 21 bears identical to process... ;) It is really hard to make this as a formal testing, unless you have unlimited bear supply... - field expert conclusions, which may be mistaken as any human opinion.

Thanks, Vassili.
 
I just read "Super Knives and Unanswered questions" by Michael S. Black. He cutting same rope same way I do but I was able to cat 800 times with 8 blades I tested and he report for some knives results lower then 500. And statement like - 70% of knives are in the "servicable" and "good" cutting range" - meaning they are were not able to cut more then 150 time is strange to me after I cut 800 times each (I cut 700 times with 420HC, but for sure I able to cut to 800). In my case reason whyle I stop - that it is clear that they will all cut further without too much problems.

I may suspect that author most likely cut it all on some - same of different cutting board which actually contribute a lot to blade dulling as well as contribute quite randomly - you may hit the board hard or soft or do not hit it at all - this is very important to eliminate this factor with simple gadget.

Also I do not really see what was criteria to stop cutting? Plus I think if he did so much testing - it will be really interesting to see tables with data.

Based on this it is really hard to do any conclusions. Like supersteel is a myth, etc...

Thanks, Vassili.
 
You may be right about the cutting board. I tested several knives by cutting through 1/2" nylon rope on an oak block, with the apparatus sitting on a kitchen scale. With some knives I was getting very low numbers of cuts, stopping when it required more than 10lbs of force on scale to cut through rope. My test was not particularly accurate, but I noticed a big difference between the beginning sharpness and the sharpness 15-30 cuts later. This makes me think you may be right about the cutting surface. I watched your video for the first time just now, and I have to say I really like your jig for rope cutting.
As far as the article, I read it as well. While his testing method was different from yours, didn't he come to a similiar conclusion?
 
Any Cal. said:
You may be right about the cutting board. I tested several knives by cutting through 1/2" nylon rope on an oak block, with the apparatus sitting on a kitchen scale. With some knives I was getting very low numbers of cuts, stopping when it required more than 10lbs of force on scale to cut through rope. My test was not particularly accurate, but I noticed a big difference between the beginning sharpness and the sharpness 15-30 cuts later. This makes me think you may be right about the cutting surface. I watched your video for the first time just now, and I have to say I really like your jig for rope cutting.
As far as the article, I read it as well. While his testing method was different from yours, didn't he come to a similiar conclusion?
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It is hard to came to any conclusion if your test is in question. He sad 70% of knives did not pass 150 cuts while all mine pass 800 and will pass more - on the same 1/2" manila rope. As I sad to me it looks like there is some other factor involved in his test which compromize results (I doubt that this is my SuperNatural strength which makes me cut rope while other can not). As well as there is no real data provided as well as there is not clear criteria of test finish.

I did not yet come to any conclusion - I personally think Lauri PT is the winner. I think CPM 440V shows excellent results so far especially in comparison with one which is "better" - CPM S30V. So in terms of comparing steel it is clear that we may say - one is better then other (in terms of 1/2" manila rope cutting).

Article only show that it is extremely important to carefully formalize testing to have stable results.

Thanks, Vassili.
 
By conclusion, I meant that both of you have decided that "super steels" do not necessarily perform better at a particular task. You have mentioned that you do not believe the steel type makes that big a difference, which was the point of his article. I realize you have not decided on a favorite.

I see your point though, that due to his testing methods, he cannot necessarily draw a proper conclusion. You could say, however, that his testing showed the best steels for cutting onto a hard surface, with all the mechanics that involved, I think.
 
My point more like every steel has some advantage over other, rather then - there is no difference between them.

Thanks, Vassili.

P.S. Like My point is "Junk steel is a myth", rather then "Super steel is a myth"...
 
I hit the base by accident with Busse (because it has thick edge it take more pressure to cut and I need to be more careful) - result came right away, sharpness test jumps from 60 to around 120. I am so disappointed - now I have to retest it again! I'll do it after I finish with Spydercos.

Thanks, Vassili.
 
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