Steel Edge Retention testing

Vassili,
First I would like to comment on your photography, WOW!!!! I really liked your video, it is incredible, whittlin hair. I was curious on your testing data. Does the lower the number mean the less pressure to cut through the rope? I am very interested in your testing methology.
 
catf1sh said:
Vassili,
First I would like to comment on your photography, WOW!!!! I really liked your video, it is incredible, whittlin hair. I was curious on your testing data. Does the lower the number mean the less pressure to cut through the rope? I am very interested in your testing methology.
Click to expand...

You are reffering to Summit thread I guess.
The number indicate how much fores I need to cut tiny cotton thread (size #10) - this indicates edge sharpness. After I sharpen knife I start cutting manila rope 1/2" after certain number of cuts of manila rope (each cut initially) I check sharpness cutting thread. I explained it in first posts in details.

So far Friction Forged D2 shows astonishing results. Way ahead of 3 other steel I tested! However it is far from finish and let see how it will do after 500 cuts...

Thanks, Vassili.
 
db said:
I have found that cardboard will fairly quickly dull an edge. I think it would be interesting to find out if different things will give different dulling results. Good idea to finish one test and then try another.
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I'll second this. Cardboard, when you can get enough of the same stuff, can separate the men from the boys pretty quickly.

There's another aspect to all this testing that I haven't heard anyone bring up yet, so I will. I can take a knife with good steel and a super edge, and keep the edge a fairly long time when pushcutting cardboard or rope. Most (not all) knives, will dull MUCH quicker if I take that same edge and slice the media. I'm wondering, if at the molecular level at the very edge, slicing doesn't allow the edge to be supported by the primary grind, and rips the edge off/out. The knives that don't dull quicker, I've found, are the ones with high carbide steel - CPM 10V, to be exact.

Anyone else ever notice this?
 
sodak said:
I'll second this. Cardboard, when you can get enough of the same stuff, can separate the men from the boys pretty quickly.

There's another aspect to all this testing that I haven't heard anyone bring up yet, so I will. I can take a knife with good steel and a super edge, and keep the edge a fairly long time when pushcutting cardboard or rope. Most (not all) knives, will dull MUCH quicker if I take that same edge and slice the media. I'm wondering, if at the molecular level at the very edge, slicing doesn't allow the edge to be supported by the primary grind, and rips the edge off/out. The knives that don't dull quicker, I've found, are the ones with high carbide steel - CPM 10V, to be exact.

Anyone else ever notice this?
Click to expand...

I do combination of push and slice when cutting rope. You may see it on video. It is same combination used in normal cutting.

Thanks, Vassili.
 
sodak said:
I'll second this. Cardboard, when you can get enough of the same stuff, can separate the men from the boys pretty quickly.

There's another aspect to all this testing that I haven't heard anyone bring up yet, so I will. I can take a knife with good steel and a super edge, and keep the edge a fairly long time when pushcutting cardboard or rope. Most (not all) knives, will dull MUCH quicker if I take that same edge and slice the media. I'm wondering, if at the molecular level at the very edge, slicing doesn't allow the edge to be supported by the primary grind, and rips the edge off/out. The knives that don't dull quicker, I've found, are the ones with high carbide steel - CPM 10V, to be exact.
Click to expand...

Here here. How much quicker does a 2" slice dull versus a 3" slice through 5/8" manilla or 6"strips of cardboard? With a natural push cut, there is always some slice used, and how much could be important to the results. When friction is a consideration in the cut (almost all real cutting uses some slice), then the wear resistance provided by the carbides can be an important factor - maybe much more important than the still undefined (at least on BF) property of edge stability. This is one reason I like the idea of machine testing for slicing edge retention (not to mention the objections based on transient lateral forces are unproven to my mind) - all cutting motions and forces are constant from cut to cut, and results are obtained directly from cutting the material causing the dulling. I may have extrapolated your comment further than you intended...

All that said I still like hand testing, and think good results can be obtained with one tester, experience, practice, and multiple runs. I like Noz's method also, and think it would really be awesome to add microscopic edge pics to similar tests (they are a great addition to any testing).

Thanks again for sharing your results, Noz. I still gotta get one of those FFD2 knives (kinda waiting on the tactical, too).
 
does the length of slice matter in 1/4" thick cardboard or 1/2" thick rope? You're dulling more of the edge, but what is dulled is by the same amount, isn't it?
 
hardheart said:
does the length of slice matter in 1/4" thick cardboard or 1/2" thick rope? You're dulling more of the edge, but what is dulled is by the same amount, isn't it?
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The length of slice is arbitrary, but should be constant for all test runs if you want comparable results.

I'll be looking forward to hearing more FFD2 results.
 
hardheart said:
does the length of slice matter in 1/4" thick cardboard or 1/2" thick rope? You're dulling more of the edge, but what is dulled is by the same amount, isn't it?
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No. What I'm trying to say is that when you push cut, the edge is supported by the grind and doesn't deform much if it is hardened properly. If you slice, the edge is being abraded parallel to it, or close, and is much more likely to rip out. I've seen knive go dull very quickly with slicing, but go dull slowly with push cutting. Try it on polyester rope and you'll see what I mean.
 
I got that part, I just mean that for any portion of the edge, the max wear it would see in a single pass would be the width of the media. If you put a mark above the edge, and place that at the front of a piece of 1/2" manila, once knife is drawn back 1/2", the mark is at the rear of the rope and it doesn't matter if you slice another 1, 2, or 10 inches for that particular spot on the edge.
 
hardheart said:
I just mean that for any portion of the edge, the max wear it would see in a single pass would be the width of the media.
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But the wear would also be influenced by other factors than distance traveled through the media. Speed, force, edge finish I think would also influence how much wear is caused in "X" slice distance.
 
oh yes, definitely, it's just that all that is going to take place a slicing distance equal to media thickness. Downward force and speed would be important measures, got a paper somewhere on the effect of slicing speed, actually. Thing is, that's not terribly easy to control/measure by hand.
 
Broos said:
But the wear would also be influenced by other factors than distance traveled through the media. Speed, force, edge finish I think would also influence how much wear is caused in "X" slice distance.
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Well, many factors may influence in theory. I may also add humidity and temperature - for sure it affects hanging newspaper sharpness test. But this influence may be not noticable in realo world. Or even being noticable - not practical. Like difference between 5 mile per hour cutting and 10 mile per hour cutting - mean nothing for me, I do not really care, I guess.

This test just provide some approximation to real world experience and may as any such research be too from real knife tasks. I believe that this test gives some idea of edge retention, however to really know how many deers or boars can be prepared without resharpening you need to prepare deer and boars until it will be dull!

I do not know how many rope cuts are equal to one deer (if there are any relations between rope cuts and deer preparations). I need good number of deers to prepare to have statistically reliable results... :eek:

So again it is just more or less abstract exercise - just FYI nor more.

And other important factors are out of scope - what happen when you use your knife for chopping, etc.

Thanks, Vassili.
 
Last cuts for Friction Forged D2 from 180 to 220 is really all around 85. Actual tests looks like this:

190

070 ++
080 ++++++++X+
090 +++++++
100 +
110 +

200

070 +
080 ++++++++
090 +X+++++
100 +++
110 +
120 +

- all more or less like this. So median in or almost in between 80 and 90. And one or two tests in that or this faivor may swing median on other side. So in general it is border value and this is why it is jumping from 80 to 90 and back. I think sharpness real is 85 and did not change too much.

Thanks, Vassili.
 
Interesting results so far, can't wait to see the completion of the testing for the FF D2 knife.
 
I have to stop this testing due to the possible allergic reaction I have on manila rope dust - this cold I have, seem to take too long, longer then usual. It is like I got better and then have it back right away. So I stop cutting ropes.

Sorry.

However, method of edge retention testing seems to be effective. I need to find better media to cut - which may not be too easy, I guess many media will release some dust to cause troubles like this. May be I do some set up inside box covered by glass or something, but for now I am not sure when I will continue this.

Thanks, Vassili.
 
Sorry to hear about your cold, Vassili. But you know, regardless of allergies, when ever dealing with good amounts of dust wearing a respiratory filter is paramount! Hope you recover quickly!
 
HoB said:
Sorry to hear about your cold, Vassili. But you know, regardless of allergies, when ever dealing with good amounts of dust wearing a respiratory filter is paramount! Hope you recover quickly!
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Cutting rope does not really produce too much dust at least visible - unfortunately it is not like sanding or grinding, where it is obvious. I need to take pause for sure and then may be continue with filter or something. And my wrist also need a rest.

I also need to rethink this - cutting rope 50 times or even 20 is too much, I need to switch media I think instead of increasing number of cuts.

Thanks, /Vassili.
 
nozh2002 said:
I also need to rethink this - cutting rope 50 times or even 20 is too much, I need to switch media I think instead of increasing number of cuts.
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This is why CATRA uses silica-impregnated paper. It dulls knives much more quickly. And if you used the thread-cutting test to measure sharpness, I'd be OK with the use of CATRA media. But I think that the CATRA media actually dulls knives too quickly. It's almost like testing a blade by shaving off part of a sharpening stone.

Hope you get better!

Carl
 
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