Visualizing the Tradeoff of Higher Hardness

[Synov]

When the graph says Total Cards Cut in mm, I am not sure how to visualize that.

The stack of cards cut has a height in mm? I'm making an assumption here that is what the chart is showing. But the stack of cards to be cut has a width too...is it 2cm to 4cm? So the stack cut is for example, "500mm high x 2cm wide" ?

It's just the height of the stack of cards. The width is always the same so doesn't matter. Here is a video of the test:

[Naperville]

When the graph says Total Cards Cut in mm, I am not sure how to visualize that.

The stack of cards cut has a height in mm? I'm making an assumption here that is what the chart is showing. But the stack of cards to be cut has a width too...is it 2cm to 4cm? So the stack cut is for example, "500mm high x 2cm wide" ?

It's just the height of the stack of cards. The width is always the same so doesn't matter. Here is a video of the test:

Interesting video. But the video raises even more questions. I'll have to take a look at Larrin's site and see if he explains this more.

Lets say the chart shows 500 Total Cards Cut for some particular steel. That is only 1.64042 feet. It looks like the stack of cards to be cut is being moved over a 1 inch area of the blade. Are they saying that that one inch of blade can only cut 1.64042 feet of card material?

See what I am getting at. I think we need more info on what these numbers mean in the real world.

[Naperville]

https://knifesteelnerds.com/categories/

[Naperville]

@Larrin

What I am trying to find out is - if I worked for a beef packing company and was cutting beef, how many feet of material can a reasonably high wear resistance steel plain edge knife with a 20 degree to 24 degree edge, EFFORTLESSLY CUT IN FEET, and does TCC tell us this information?

I realize that those working in slaughter houses carry a steel to sharpen their knives.

What did soldiers / swordsman do in the medieval era? Did they have sharpening services at the battles?

It looks like if I want to cut a lot of material (depth per cut in mm) I need to use a high wear resistance steel and stay at or below 5 to 10 cuts, then resharpen.


Trying to learn what I could about CATRA I came across the following interesting information:

Most useful might be:
https://knifesteelnerds.com/2020/05/01/ ... fe-steels/


https://knifesteelnerds.com/2018/06/18/ ... retention/
"...if the edge angle of a 154CM knife is reduced from 30° to 20° then it can match or exceed a steel with 75% greater wear resistance."

"Thinner edges, regardless of final edge angle, did have a small advantage in edge retention..."

"...it appears that 600 grit did marginally better than 320 or 8000 grit" for TCC.

"Surprisingly the steel without cryo had slightly better edge retention, though the difference is small."


https://knifesteelnerds.com/2018/11/19/ ... retention/
/QUOTE/
Summary
The CATRA test tells us the loss in cutting ability during slicing of highly abrasive media. It is highly affected by edge geometry and therefore we can’t necessarily simplify the test to a comparison of different steel + heat treatment combinations without maintaining all other variables the same. Reducing the edge angle (20° edges cut longer than 50° edges) strongly improves cutting ability and the CATRA TCC values indicating higher overall edge retention. There is a stronger difference between high and low wear resistance steels at low edge angles than at high edge angles primarily because with high edge angles the knives cut much less cardstock. With a fixed edge angle of 30° there were steels that cut from 180 mm all the way to 850 mm TCC, showing that steel also has a strong effect on edge retention. The steel with the highest slicing edge retention has the maximum amount of vanadium carbide and it is heat treated to a high hardness. Therefore among available knife steels we would expect a steel like 15V or Rex 121 to have the best slicing edge retention because of the high MC carbide volume.
/END QUOTE/

https://knifesteelnerds.com/2018/11/26/ ... etention2/
/QUOTE/
Regression Factors Analysis

In part 1 I described the process by which we calculated the relative factors that affect edge retention which resulted in the equation below. CrC is a general term to refer to either Cr7C3 or Cr23C6 chromium carbides. CrVC is a general term to refer to M7C3 where M can be either Cr or V; when vanadium is added to a high chromium steel the chromium carbides are enriched with vanadium which increases the hardness of the Cr carbides. MC can refer to either vanadium carbides (VC) or niobium carbides (NbC). MN can refer to either vanadium nitrides (VN) or niobium nitrides (NbN). CrN refers to chromium nitrides. The formation of these particles is controlled primarily by the composition of the steel and secondarily by processing and heat treating. The equation below and the tables in Part 1 and here in Part 2 come from journal articles and books that have reported the carbide fractions after heat treatment.

TCC (mm) = -157 + 15.8*Hardness (Rc) – 17.8*EdgeAngle(°) + 11.2*CrC(%) + 14.6*CrVC(%) + 26.2*MC(%) + 9.5*M6C(%) + 20.9*MN(%) + 19.4*CrN(%)
/END QUOTE/


https://knifesteelnerds.com/2019/02/11/ ... rformance/

[Synov]

Lets say the chart shows 500 Total Cards Cut for some particular steel. That is only 1.64042 feet. It looks like the stack of cards to be cut is being moved over a 1 inch area of the blade. Are they saying that that one inch of blade can only cut 1.64042 feet of card material?

The area of the blade doesn't matter since the stroke always remains the same. It's not saying the knife can only cut that amount of material, it's saying that's how much it will cut using the same force and the same amount and type of strokes as the machine. The number has no real practical meaning by itself, only when compared to other CATRA test results does it tell us how much the knife edge will last in relative terms.

[Naperville]

Lets say the chart shows 500 Total Cards Cut for some particular steel. That is only 1.64042 feet. It looks like the stack of cards to be cut is being moved over a 1 inch area of the blade. Are they saying that that one inch of blade can only cut 1.64042 feet of card material?

The area of the blade doesn't matter since the stroke always remains the same. It's not saying the knife can only cut that amount of material, it's saying that's how much it will cut using the same force and the same amount and type of strokes as the machine. The number has no real practical meaning by itself, only when compared to other CATRA test results does it tell us how much the knife edge will last in relative terms.

OK, I agree with that. That seems logical.

Note that we still do not have a test to tell us how much of any given material some knife with attributes X, Y, Z cuts in the real world. Until we can extrapolate from the TCC some equivalent material with a certain amount of force we will never know.

Because leather has variances in it, I would use vinyl fabric for furniture as a cutting medium. It would be nice to be able to say, "with this knife steel with attributes X, Y, Z, .... and Silvertex Residential Vinyl Fabric by Spradling we were able to cut 2750 linear feet off material using less than 10ft-lbs of pressure." And here are the specs on the vinyl: https://jtsoutdoorfabrics.com/silvertex ... ex_sunkist

[Deadboxhero]

Lets say the chart shows 500 Total Cards Cut for some particular steel. That is only 1.64042 feet. It looks like the stack of cards to be cut is being moved over a 1 inch area of the blade. Are they saying that that one inch of blade can only cut 1.64042 feet of card material?

The area of the blade doesn't matter since the stroke always remains the same. It's not saying the knife can only cut that amount of material, it's saying that's how much it will cut using the same force and the same amount and type of strokes as the machine. The number has no real practical meaning by itself, only when compared to other CATRA test results does it tell us how much the knife edge will last in relative terms.

OK, I agree with that. That seems logical.

Note that we still do not have a test to tell us how much of any given material some knife with attributes X, Y, Z cuts in the real world. Until we can extrapolate from the TCC some equivalent material with a certain amount of force we will never know.

Because leather has variances in it, I would use vinyl fabric for furniture as a cutting medium. It would be nice to be able to say, "with this knife steel with attributes X, Y, Z, .... and Silvertex Residential Vinyl Fabric by Spradling we were able to cut 2750 linear feet off material using less than 10ft-lbs of pressure." And here are the specs on the vinyl: https://jtsoutdoorfabrics.com/silvertex ... ex_sunkist

A good test is not about making a universal conversation to all aspects of use.

It's about making a controlled comparison for seeing how things would stack up if everything was "equal"

Testing works best when we isolate a specific property like wear, toughness or strength rather than trying to test them all together at once.

I wouldn't get lost in "how many licks to the center of the Tootsie Pop."

Yes, end users are the biggest variable not the materials.

For example,


We can give the world's greatest knife to two completely different end users and ask them to open a bag of gravel.

User 1: Carefully opens the plastic gravel bag with a precise slice at the top of the bag without contacting anything hard.

User 2: Stabs the blade deep into the gravel bag, and slashes the edge through the rocks to burst open the bag.

These users will have very different experiences despite using the same knife for the same task.

Either style of use requires completely different geometry to function best regardless of materials.


Does that make all testing invalid?


Nope.

Good testing is very useful to understand the trade offs a material or condition can offer in perspective of other materials and conditions.

Then the end users and manufacturers can then decide how to maximize the strengths and avoid the weaknesses.

This is the true magic of best performance.

When done correctly it makes "the best" despite there being no "best"

"Magic" happens when the end user is completely unaware of these trade offs being optimized; the behind the scenes factors making something work "best."

[Bolster]

… A good test is not about making a universal conversation to all aspects of use. It's about making a controlled comparison for seeing how things would stack up if everything was "equal" ...

^ That's a super important point. This is known as the attribute of 'internal validity' and it's essential to scientific investigation. It's typically established first, and tests of 'external validity' follow (what folks on this forum are calling 'real world' testing), which in this case might be: do CATRA scores and controlled tests in some other consistent medium correlate highly? If they don't, the researcher may have found an edge attribute that CATRA doesn't measure, given CATRA's focus on slicing edge retention in an abrasive medium.

Larrin did some of this work already. He examined three other data sets: Cedric&Ada's sisal rope cut tests, Ankerson's manilla rope tests, and Sandor's rope tests. Most of these data were only partly controlled. For example, the amount of force used, thickness BTE, hardness, motion and range of cut, and other variables weren't controlled, for most of the data. Uncontrolled variables like these introduce a lot of variability and reduce the potential size of the correlations. Still, if CATRA has external validity, we shouldn't see contradictions with other “real world” tests; that is, we shouldn't see low correlations or negative correlations.

Cedric&Ada's tests gave results of R-squared=.66; Ankerson's tests had R-squared=.68; and Sandor’s tests gave R-squared=.65 with one outlier removed. If you think in correlations in stead of R-squared, these translate into correlations of r= .81, .82, and .81, respectively. In other words, large associations…especially given the number of uncontrolled variables. So for rope cutting, at least, CATRA is highly predictive of at least three other available datasets. Another way of saying this, is that these three “real world” rope tests don’t appear to be measuring much that CATRA isn’t already measuring.

None of this is to say that CATRA’s sandy cards are the be-all-end-all test medium. There may be other test media that measure other aspects of slicing edge retention. On the other hand, it appears that industry has standardized on CATRA for good reason; so far it appears to be a test that does a good job of quantifying slicing edge retention in other media, not just silica-impregnated cards.

[Deadboxhero]

Hi Steeltoes,

Was if finished? Did you use it?

sal

Sal, I'll just make ya one and you can test it.

Love to Shawn. Almost like a new steel, and one that I chose for our introduction of powdered metals into the production market.

I'd like to pay for it or trade you something. If it works well, we might add it to the Mule queue?

Sorry to hijack your thread synov. Back to it.

sal

Alright, I'll get it going and start a new thread.

[Steeltoez83]

I prefer to run my own tests and make comparisons on what I'm able to achieve with my own edges. I think CATRA testing gets the conversation started when performance is being investigated and discussed.

[Bolster]

I prefer to run my own tests and make comparisons on what I'm able to achieve with my own edges. I think CATRA testing gets the conversation started when performance is being investigated and discussed.

Kudos! Trying to remember what you use as a medium. Are you the fellow who uses blocks of ice? Would you consider your tests as assessing slicing edge retention (like CATRA) or does your test measure something else? Have you checked the correlation between your tests and published CATRA scores?

[Steeltoez83]

I prefer to run my own tests and make comparisons on what I'm able to achieve with my own edges. I think CATRA testing gets the conversation started when performance is being investigated and discussed.

Kudos! Trying to remember what you use as a medium. Are you the fellow who uses blocks of ice? Would you consider your tests as assessing slicing edge retention (like CATRA) or does your test measure something else? Have you checked the correlation between your tests and published CATRA scores?

I've never compared my tests to CATRA results. I was asked a few questions about my methods in the mule section of the forum so I wrote a more detailed explanation of what I do and why I do it there. It's under the b70p thread if you care to read it. Right now I'm testing the s60v knife I mentioned earlier in this thread.

[Naperville]

Lets say the chart shows 500 Total Cards Cut for some particular steel. That is only 1.64042 feet. It looks like the stack of cards to be cut is being moved over a 1 inch area of the blade. Are they saying that that one inch of blade can only cut 1.64042 feet of card material?

The area of the blade doesn't matter since the stroke always remains the same. It's not saying the knife can only cut that amount of material, it's saying that's how much it will cut using the same force and the same amount and type of strokes as the machine. The number has no real practical meaning by itself, only when compared to other CATRA test results does it tell us how much the knife edge will last in relative terms.

OK, I agree with that. That seems logical.

Note that we still do not have a test to tell us how much of any given material some knife with attributes X, Y, Z cuts in the real world. Until we can extrapolate from the TCC some equivalent material with a certain amount of force we will never know.

Because leather has variances in it, I would use vinyl fabric for furniture as a cutting medium. It would be nice to be able to say, "with this knife steel with attributes X, Y, Z, .... and Silvertex Residential Vinyl Fabric by Spradling we were able to cut 2750 linear feet off material using less than 10ft-lbs of pressure." And here are the specs on the vinyl: https://jtsoutdoorfabrics.com/silvertex ... ex_sunkist

A good test is not about making a universal conversation to all aspects of use.

It's about making a controlled comparison for seeing how things would stack up if everything was "equal"

Testing works best when we isolate a specific property like wear, toughness or strength rather than trying to test them all together at once.

I wouldn't get lost in "how many licks to the center of the Tootsie Pop."

Yes, end users are the biggest variable not the materials.

For example,


We can give the world's greatest knife to two completely different end users and ask them to open a bag of gravel.

User 1: Carefully opens the plastic gravel bag with a precise slice at the top of the bag without contacting anything hard.

User 2: Stabs the blade deep into the gravel bag, and slashes the edge through the rocks to burst open the bag.

These users will have very different experiences despite using the same knife for the same task.

Either style of use requires completely different geometry to function best regardless of materials.


Does that make all testing invalid?


Nope.

Good testing is very useful to understand the trade offs a material or condition can offer in perspective of other materials and conditions.

Then the end users and manufacturers can then decide how to maximize the strengths and avoid the weaknesses.

This is the true magic of best performance.

When done correctly it makes "the best" despite there being no "best"

"Magic" happens when the end user is completely unaware of these trade offs being optimized; the behind the scenes factors making something work "best."

You may have positive points for selling knives to some people, but 95% or more of the people that buy knives do not understand that there are better steels worth purchasing.

If somebody wise, talented, and resourceful could come up with accurate tests for (we will guess) the top 5 materials that reflect a wide use base (to cut) and show how the tests work in a beneficial manner for high end steels, the market would break wide open for somebody like Spyderco.

Test and reveal the benefits of different steel for cutting the following (not just one cut, but hundreds or thousands if the steel can handle it, then show the non deformed steel and the fact that it now needs sharpening):
- brush, grass, bushes, saplings
- cotton, and vinyl of varying thicknesses
- plastics and rubbers of varying thicknesses and hardness
- paper and cardboard of varying thicknesses and coatings
- meat packing, hunting, prep for cooking

[Steeltoez83]

I can only speak about my own testing. First thing I do is test the wear resistance under ideal conditions. Production folders need 3 or more fresh edges before that even happens. I like running my edge angles low, so that's what I test with. Low edge angles are necessary for part 2 of testing. The media I use is 100 grit shop sanding rolls from red label abrasive. They come in 3 sized diameters, so I have class system what length cutting edge goes to which size roll. I have a dulling standard based on incision points from the radius of the apex. Once I'm able to determine what the wear resistance is, I can start implementing other dulling mechanics. I use a 1k edge which is a happy medium between draw cutting and push cutting. Knife use that's centered around mostly draw cutting would be better suited for an edge finish below 1k. Now part 2 of testing, after a fresh edge is applied I do the same test but stop at 40%. Then I throw a different blunting mechanic into the equation. Right now it's 20% but that can change. I use a block of ice for this portion. Low edge angles are not ideal for these movement patterns especially with high carbide alloys. Once I hit 60% I test the edge, and continue draw cutting til the apex fails my own set standards. I call it a chop motion, but it's designed to balance out the draw cutting. And to get a better view into what the steel can do. Alot of toughness testing is based on the blade geometry. I try to make my own testing applicable and base my own conclusions of what the apex is able to do.

[Bolster]

I can only speak about my own testing. First thing I do is test the wear resistance under ideal conditions. Production folders need 3 or more fresh edges before that even happens. I like running my edge angles low, so that's what I test with. Low edge angles are necessary for part 2 of testing. The media I use is 100 grit shop sanding rolls from red label abrasive. They come in 3 sized diameters, so I have class system what length cutting edge goes to which size roll. I have a dulling standard based on incision points from the radius of the apex. Once I'm able to determine what the wear resistance is, I can start implementing other dulling mechanics. I use a 1k edge which is a happy medium between draw cutting and push cutting. Knife use that's centered around mostly draw cutting would be better suited for an edge finish below 1k. Now part 2 of testing, after a fresh edge is applied I do the same test but stop at 40%. Then I throw a different blunting mechanic into the equation. Right now it's 20% but that can change. I use a block of ice for this portion. Low edge angles are not ideal for these movement patterns especially with high carbide alloys. Once I hit 60% I test the edge, and continue draw cutting til the apex fails my own set standards. I call it a chop motion, but it's designed to balance out the draw cutting. And to get a better view into what the steel can do. Alot of toughness testing is based on the blade geometry. I try to make my own testing applicable and base my own conclusions of what the apex is able to do.

^ That's impressive. I like that you mix "dulling mechanics" (sandpaper and ice) at set percentages of edge wear. Also very interesting to mix cutting styles (draw, push, chop). Remind me, do you publish your results?

[Steeltoez83]

I can only speak about my own testing. First thing I do is test the wear resistance under ideal conditions. Production folders need 3 or more fresh edges before that even happens. I like running my edge angles low, so that's what I test with. Low edge angles are necessary for part 2 of testing. The media I use is 100 grit shop sanding rolls from red label abrasive. They come in 3 sized diameters, so I have class system what length cutting edge goes to which size roll. I have a dulling standard based on incision points from the radius of the apex. Once I'm able to determine what the wear resistance is, I can start implementing other dulling mechanics. I use a 1k edge which is a happy medium between draw cutting and push cutting. Knife use that's centered around mostly draw cutting would be better suited for an edge finish below 1k. Now part 2 of testing, after a fresh edge is applied I do the same test but stop at 40%. Then I throw a different blunting mechanic into the equation. Right now it's 20% but that can change. I use a block of ice for this portion. Low edge angles are not ideal for these movement patterns especially with high carbide alloys. Once I hit 60% I test the edge, and continue draw cutting til the apex fails my own set standards. I call it a chop motion, but it's designed to balance out the draw cutting. And to get a better view into what the steel can do. Alot of toughness testing is based on the blade geometry. I try to make my own testing applicable and base my own conclusions of what the apex is able to do.

^ That's impressive. I like that you mix "dulling mechanics" (sandpaper and ice) at set percentages of edge wear. Also very interesting to mix cutting styles (draw, push, chop). Remind me, do you publish your results?

Not currently. I have been asked quite a few times tho. I rarely check my edge angles before testing on my goniometer but it usually hovers around 12 dps for testing. I feel that's vital info required before publishing any formal charts to reference. My bd1 manix performs poorly compared to my bd1 polestar. My xhp Para 3 is 63 hrc in xhp which is likely to hit higher test numbers compared to other xhp. Both my 15V test samples tested different values, so the results are the average of 2 results. The 10V I just tested had the same results on 2 samples (pm2/para3). When Sal became interested in my test methods I was testing a custom heat treat, I offered to journal the testing and the outcome here. Sal politely requested I keep to spyderco products on this forum. Eventually I might just make a dedicated thread and list the results here for production steels from spyderco.

[sal]

Hi Steeltoez,

It wouldn't hurt my feelings to see a compilation of Spyderco steels as a dedicated thread. Though I would be interested to know if there were any other companies getting better performance than Spyderco on similar steels?

sal

[Steeltoez83]

From what I've tested from buck, their s30v is a contender. Id have to retest to give specific values tho. I have tested s35vn and s45vn from other brands and spyderco outshines every sample I've tested so far.