Matus wrote: ↑Mon Jan 17, 2022 2:08 am
Deadboxhero wrote: ↑Mon Jan 17, 2022 12:44 am
Matus wrote: ↑Mon Jan 17, 2022 12:29 am
This is going to be a very tool study / testing / comparison. Thanks for all the work Shawn.
Any predictions?
It is hard to separate wishes from predictions :)
I see the most important properties as a triangle of (1) edge retention, (2) toughness and (3) edge stability. We know that different steels offer different compromises in this regard. On top of that there are a bit more subjective properties like how do the steels react to sharpening, how do they hold coarse or fine edge, etc.
We have seen tests by Larrin and by some users (like Outpost 76) when it comes to edge retention, so the should not be any particular surprises - but that is yet to be seen. For me personally it is the (a little more elusive) edge stability of the main interest as we are talking pocket knives, not machetes, where the toughness would be probably the leading property. And in particular the balance of edge stability and edge retention. So I am very curios whether you will manage to come up with some testing that could give us a better feel about the edge stability (maybe scraping on some nasty stuff like hard plastics or brass, or applying torque with some fixed cut-depth - none of that is unlikely to be simple to do repeatably I fear)
A bit separate topic - I would be what will be the leading edge damage process be - chipping or rolling. For example I was surprised that the edge on my k390 PM2 (HRC measured at 63.0 & 63.5) rolled more than chipped when I by accident tried to force it into a steel wire (the knife had no chance).
I HOPE that Magnacut will come out with high edge stability at still acceptable toughness (which appears to start to take a hit somewhere above 63 HRC).I also hope to see higher edge stability for the Spy27 compared to S45VN. I feel that we still don't have a deep enough understanding of what Spy27 is actually capable of and whether it can sufficiently differentiate itself from the S30V/S35VN/S45VN crowd. I am curios whether Spy27 and Magnacut will manage to 'outperform' the M390 in some regard.
A lot will depend on HRC of the tested knives. Should the Magnacut be around 63 HRC, than I would predict that it should outcut Spy27 and S45VN. I would be very curios to see a direct comparison to S30V, as that particular steel gets very high edge retention in Larrin's testing.
BTW, if you would like to include a k390 PM2 just let me know.
Excellent response.
I wanted to use this testing to measure the retention of the front end sharpness which I felt like is possible using this bess tester.
A qualitative reference for BESS testing values, 100-150g is a sharp edge. We lose that front end sharpness the closer we get to 300g and it will no longer shave hair going past 300g and near 400g we start losing the ability to consistently cut paper cleanly.
It's no secret that carbides will kick in and keep a working edge from ever going truly blunt with varying degrees of carbides and hardness of course.
So, I thought it would be fun to have this test structured around seeing the loss of front end sharpness. Which seems to happen around a hundred cuts in 3/4" Manila for most steels depending on the edge geometry and finish of course.
There's often arguments about lower carbide volume steels having better front and sharpness and higher carbide volume steels and some folks saying that hardness doesn't matter and hardness does matter.
So it should be fun to see. Make for good arguments and deeper conversation about what we all love.
I think with the sharpening being probably the greatest factor for all performance, it will be interesting to put these on the same level of sharpness with the same amount of cuts and see which one maintains its sharpness especially with using cubic boron nitride abrasives to cut all the phases inside the steel, rockwell hardness of course does not reveal the hardness of the individual carbides. As we know, carbides can vary in hardness themselves based on the different kinds and are throughout the microstructure. Also rockwell hardness testing doesn't reveal small percentages of detrimental softer phases hiding in the small crevices of the microstructure which can vary with different heat treatment.
Cut it all is what I say.
I've noticed constant forum threads across different forums and different conversations in different Facebook groups of folks saying that they're experiences have varied so wildly from what is published in more controlled testing.
I've seen some folks make conclusions that the testing is then invalid.
When I see differences between control testing and use it really shows the power of sharpening and what the variation can do for edge retention.
I find we're all doing things differently with how we feel like we get the best result for what we consider a good edge or good enough edge without overthinking it.
So, perhaps that's another piece of the puzzle to explore? We can send these knives or other knives to people to have them sharpen them get them back and test them just to see the changes from different kinds of sharpening.
Maybe instead of testing knives and steel we should be testing ourselves.
I think people are the most interesting and greatest variable of all.
I have a theory that perhaps chromium carbides are the "people's carbide" because some do not believe that they need cBN or Diamond to sharpen steels that have an abundance of carbides that are harder than the alumina abrasive in their ceramic stones and they will not be able to cut the apex as flush and crisp when setting the initial edge leading to loss of front end sharpness prematurely in my experience.
That would be interesting in not only testing these knives but also the real world influence of people that use them and form different opinions about them based off their personal experiences that can vary so widely for this reason.
Perhaps we could quantify these different experiences?
It's not to say that there isn't variability in cutting rope.
There's inherent variability in everything if we choose to look at something close enough. Of course that's why anytime we collect data we take an average, even the rockwell hardness testing under the strictest rules of metrology with a $100,000 tester in a lab, they will still take an average of readings.
Just sharing some of my thoughts and opinions.
