Steel Edge Retention testing

I don't know but Larrin posted these micrographs a while back:
ATS-34:


S30V:


D2
 
I have to agree with PghMitchS02 that all this playing with numbers really prove the old saying about lies, damn lies & statistics, but I can't believe there hasn't been more discussion about edge thickness.

Vassili, while I agree with you about the length and weight of the knife not mattering because of the way you are doing the testing, I really think that edge thickness has to play a significant part even if you are matching edge angles. Considering how much work you are putting into this, why not eliminate this as a variable? I think it would make this particular test much more valid.

For those who disagree with this, please explain where I went wrong. -Mike
 
I think almost all of the talk of coarse grain and large carbides of most steels comes from a single source, and has been repeted by many many posters.
Mike I think the thread is so thin that it is cut before the blade thickness is an issue.
 
Is the heat treat on a given test knife of any concern?

In asking this I do not doubt that this testing is valuable, but that it may not answer the questions some might want answered. For example I would guess the testing will not say which steel is "better" than another steel, but rather something along the lines of Vassili's specific knife X tested better than his knife Y.

Maybe if lots of people started contributing test results on steels prepared in various ways then some interesting consistencies might surface. That would be cool!

Vassili, good work! :thumbup:
 
mikeymoto said:
Is the heat treat on a given test knife of any concern?

In asking this I do not doubt that this testing is valuable, but that it may not answer the questions some might want answered. For example I would guess the testing will not say which steel is "better" than another steel, but rather something along the lines of Vassili's specific knife X tested better than his knife Y.

Maybe if lots of people started contributing test results on steels prepared in various ways then some interesting consistencies might surface. That would be cool!

Vassili, good work! :thumbup:
Click to expand...

Yes, sure this is why I specifically mention what knife it is etc. It is not ATS-34 but ATS-34 by Paul Bos, as well as it is not 420HC, but 420HC zero quenched in Taiwan (as I remember it was very sharp out of the box). I think I need to test Buck's 420HC against it too.

2 MVF

I already addressed it in answer to Confederate:
http://www.bladeforums.com/forums/showpost.php?p=5025786&postcount=10
I am not looking on how much force I need to cut the rope - I cut it with whatever needed and then see what happen to the edge.

BTW - rope is pretty random, sometime it is easy to cut, sometimes not, especially I can see it cutiing it 20 times in a row - force needed to cut is very different. I guess we can not relay on this parameter. Even thin thread need to be cut 21 times to get reliable result!

Thanks, Vassili.
 
db & Vassili, I am not concerned with the thread cutting or how much force to cut the rope- couldn't a thicker edge maintain itself better? -or a thinner edge cut better in spite of dulling?

I don't know which way this would go, I just think it's a variable that should be eliminated. If you're wanting to compare edge retention of the steels, the only difference should be the steels.

I imagine you think you're only measuring the very edge so only the angle matters, but the thickness of the edge, and even of the blade, could be skewing your results by the effect it may have during the rope cutting, even if it doesn't effect the thread.
 
MVF said:
db & Vassili, I am not concerned with the thread cutting or how much force to cut the rope- couldn't a thicker edge maintain itself better? -or a thinner edge cut better in spite of dulling?

I don't know which way this would go, I just think it's a variable that should be eliminated. If you're wanting to compare edge retention of the steels, the only difference should be the steels.

I imagine you think you're only measuring the very edge so only the angle matters, but the thickness of the edge, and even of the blade, could be skewing your results by the effect it may have during the rope cutting, even if it doesn't effect the thread.
Click to expand...

Oh, I see you point - this is valid hypothesis. May be too much mass behind edge affects edge deformation. It is clearly true if edge too thin, but I do not think it is the case here where edge is 1mm or so at least plus forces involved is not too big to affect steel deformation in this scale. Of course only experiment may make it clear.

Thanks, Vassili.
 
MVF said:
couldn't a thicker edge maintain itself better? -or a thinner edge cut better in spite of dulling?
Click to expand...

if Vassili sharpened the knives at the same angle, then the same wedge of steel is cutting through the thread. The thread is smaller in diameter than the height of the edge bevel. Is there some way to load the edge more while cutting the rope? The individual fibers will cut like the thread does, and wedging is going to happen at the primary grind, not at the edge. Seems that the sharpness of the edge is going to determine how hard the rope fibers push back against it before being cut, not how thick the spine is. and I don't think the forces are taking the steel outside the plastic region, but that would have to be measured.
 
I finish ATS-34 400 cuts and start expanding table up to 500 for sure or may be more - 600 etc.

I take Busse Game Warden which I keep untouched.

This is last measurement I did 25 Oct 2007 after 400 cuts:

400
090 +
100 ++++
110 ++++
120 +X++++
130 ++++
140 +
150 +

This one I did 1 Nov 2007 gust to make sure that there is no changes in my set up - I was surprised with 420HC results and decided that it is worse to check just in case:

400'
080 +
090
100 ++
110 +++++
120 ++X+++++
130 +++
140 +
150 +

As you may see results are almost identical.

Today 6 Nov 2007 I take it again wash with warm water and soap and again test sharpness before start another session to make sure nothing happen to knife.

400''
090 +
100 ++
110 ++++++
120 +X+++++
130 ++
140 ++
150 +

Again results are almost identical - median 120 on the second position in the row.

Now after 20 cuts it turns into 110 back!

420
090 ++
100 +++++
110 +++X++
120 ++++++
130 ++

What a crazy steel - INFI! It may dull to 130 and then came back to 110.

I am absolutely certain that this is crazy evolution of steel itself and not really related to test method or something. ATS-34 behave much more predictable. Interesting...

Thanks, Vassili.

P.S. Again there is no steel better or worse - they all different all with their own individuality, attitude if you want! Each has it's bright side!
 
Vassili, given your above post about the "crazy evolution" of INFI and looking over your results table I strongly suspect that your method of determining sharpness is somehow inconsistent. Your results for ATS-34 look consistent, a gradual dulling of the blade as more cuts are made. But for both INFI and 420 the results gyrate suspiciously. This just doesn't add up. I know you are taking the median of 20 tests, but nevertheless it seems that there are variances in the test taking, perhaps 20 tests done when you are fresh are not equivalent to 20 tests done when you are tired. I said this before, I think you really need to run these tests in a side by side manner. I'm not trying to be critical, I'm just seriously starting to doubt the accuracy of your results.
 
theonew said:
Vassili, given your above post about the "crazy evolution" of INFI and looking over your results table I strongly suspect that your method of determining sharpness is somehow inconsistent. Your results for ATS-34 look consistent, a gradual dulling of the blade as more cuts are made. But for both INFI and 420 the results gyrate suspiciously. This just doesn't add up. I know you are taking the median of 20 tests, but nevertheless it seems that there are variances in the test taking, perhaps 20 tests done when you are fresh are not equivalent to 20 tests done when you are tired. I said this before, I think you really need to run these tests in a side by side manner. I'm not trying to be critical, I'm just seriously starting to doubt the accuracy of your results.
Click to expand...

Tough call, really... How can I prove that I am in good medical condition to do testing?

Well, actually ATS-34 I did tested trough my cold sickness (because I have plenty of time), now I am better and even went to the office and did some work - programming.

What else?

Usually to prove that all conditions are the same I do control testing - as you may notice in my post I tested INFI November 1 and today right before I start tests - all results identical. It shows increased sharpness in comparison with today control test and only difference is that I did 20 cuts in between.

And in this case especially for you I just did another test for ATS-34 edge:

This is what I have before start getting "crazy" results from INFI

400 ATS-34
110 +++
120 +++++++
130 X+++++
140 +++++

Just finished few seconds ago

400' ATS-34
100 +
110 ++
120 +++++++
130 X+++++
140 ++++
150 +

As you may see results again identical, so I do not really know how else I may prove that crazy behavior of INFI is not because I am crazy :)

I saw this before doing my first tests attempts - like year ago. I am confident in my method and confident that this is steel somehow evolving this way. I do not see any reason why to expect smooth ideal behavior from very complicated composit material like steel when we are talking about scales close to grain sizes. So who know how steel is wearing out really and what kind of processes going on on the very edge.

So I am surprised but this does not disregard test in any way - I am again amazed by this thing - steel!

And again - it is easy to verify... Try it youself! It is easy just require some effort.

Thanks, Vassili.
 
HoB said:
Cobalt: Yawn :yawn:. How about YOU do some graphing, instead of seeing things at one glance. Or better yet, you do some of your own testing. If you did, maybe you would realize that there are no landslides in Nozh's data set.
.
Click to expand...

LOL. It appears my quick analysis at a glance from a hotel room was more accurate than your attempt at it in tons of long paragraphs. :D

Noz, what you are noticing is what I have seen for years. INFI sometimes almost seems to sharpen itself. I have told this to many on the forums, because I cannot explain it. But in order to notice this you actually have to use a knife and not talk science without ever having any real info. good job by the way and I do not mean to derail you, but seeing patterns in tests is imprortant. Thanks for your hard work.

what you will notice is that INFI will start to dull, then get sharper, then Dull then get sharper. It seems to sharpen itself over time. However, it will eventually dull since eventually the edge thickness overcomes the sharpness. I have discusses this with other hogs at length and some who actually use their knives have noticed this as well.

The only other material that I have ever noticed perform like this is Stellite 6K, but not sure that it could outlast INFI. My spyderco 440V knife had the lngest lasting edge I have ever had until about a year of use and then it dulled much more than INFI. But for several months of hard cutting it's edge lasted much longer than INFI at it's high sharpness. then when it got to a very sharp but not scary sharp point INFI lasted what seemed for ever at that point but 440V continued to dull. It then took me hours to get the edge sharpness back, while I got infi back to shaving sharpness by stroping it on canvas/fine grit.

NOZ ONE QUESTION FOR YOU:

at what gram weight would you consider a knife barely able to cut. I think this is crucial in your test. There is no way to quantify and compare the results unless you have a gram point at which a blade can barely cut thread, which would be the same point for all knives. Until then results need to be quantified as a difference not starting and ending points. The difference from beginning to end is more important than the starting point and end point. The difference shows degredation regardless of how thick the edge is, I think. This is IMO
 
INFI seems to have a certain malleability at high hardness that I have not personally experienced with any other type of steel. I have no scientific data to back that up but I did find my NO to be shaving sharp after splitting between 75 and 100 feet of bamboo when it was not so before I began. Pretty wild stuff, IMO.
 
The self sharpening of steels with significant carbides was discussed as well. I remember the main problem Cliff had with your first reports of it was that he said you were seeing it too quickly and too drastically. In this case, a 10 gram shift after 10-20 cuts in rope doesn't seem unreasonable. 500 rope cuts, and 21 thread cuts for each; there's noise, but there's a lot of data points too. Maybe it would be better to bump up the precision, 5g increments instead of 10. That would be tough to eyeball on a postal scale, though.

I had a shaving edge with a median of 190g, from 120 grit. There are precious few people in the world that have ever handled a knife that would ever measure 30g on the thread cutting, it's a very delicate and unnecessary thing on a utility tool. IIRC, Vassili said he was stropping 100 times/side to get his highest sharpness. After hundreds of rope cuts, his knives are about the same level as most quality factory fresh blades. From the first post in this thread-

ScrapYardKnives DumpsterMutt SR77 (S7) - 50
Microtech Currahee D2 - 60
Kiku Matsuda Tanto II OU31 - 60
Spyderco Military BG42 - 60
Spyderco Endura ZDP189 - 60
J.P.Holmes CPM 10V - 70
Dozier KS7 D2 - 70
Swamp Rat HRLM SR101 (52100) - 80
Busse Meaner Street Red INFI - 80
Kershaw JYD Sandvic 13C26- 90
Kershaw Cyclone ZDP189 - 90
Fallkniven P SGPS- 90
Busse BA INFI - 100 (inspected by #4)
Buck 110 CPM154 - 110
Mission MPK-S -130
Swamp Rat Mini UM SR101 (52100) - 130
Busse BA INFI - 130
Click to expand...

This also reminds me when I asked what cutting was anyway, and no one had a great answer. The thread parts at 1.5kg, and it parts at 30g. When is it no longer being 'cut'.
 
A digital scale would definitely make all of this more accurate.
 
Larrin said:
A digital scale would definitely make all of this more accurate.
Click to expand...

I have jewelry electronic scale especially bought for this - they have 0.3 sec delay and so absolutely useless! So I went back to my old scaes.

Thanks, Vassili.
 
The 420 also seems to have a "self-sharpening" capability as well going from 90 to 70 between cuts 40 and 45. Has anyone checked for nanobots.:)
 
theonew said:
The 420 also seems to have a "self-sharpening" capability as well going from 90 to 70 between cuts 40 and 45. Has anyone checked for nanobots.:)
Click to expand...

I do not see why do you think it can not be natural way? Nanobots - is an explanation of course, but very edge may bend one or other direction, it may chip on microscopic level etc...

Again I am dealing with changes on microscopic level. In addition I detect this changes on macroscopic level. Modern astronomers can detect planet near distant star, it's size and weight just by tiny blinking of star brightness. This is similar thing. Why they think that this is a planet circling star not just tiered astronomer?

Also this is numbers I read from my tests, not really pure ideal sharpness. As well as cutting rope is not pure ideal load (CATRA for example has special media to make sure that load is even).

Please - try it yourself first!

Thanks, Vassili.
 
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