I’m so frustrated with my VG10 Endura not taking a edge ( good lasting scary sharp at least)
It the highth of hunting season and my knives are getting a major workout and it was time to get back on the sharpening bench
Zero problems getting these scary sharp with 300gt to 600gt to ceramic to leather strop
1.cpm 20cv endela
2 vg10 endela
3 CPM s35vn tenacious
4 Vtoku2 stretch
5 a old stretch unknown steel
The vg10 endura last night went through the same process 3 different times and never came out to my standards for hunting field use so it’s back to the drawer till hunting season is over
Any idea what I am doing wrong?
If Stretch is frn , what color is scales ? MG2
Black G10 ? All my other stretch have different colors frn grey , orange, ect
I only have five Stretch models and only could find a frn in black . Could it possibly be the CF model in ZDP189 ? Posted old shot so you could see texture . Dan
Last edited by Manixguy@1994 on Sun Nov 24, 2024 4:43 pm, edited 1 time in total.
MNOSD 0002 / Do more than is required of you . Patton
Nothing makes earth so spacious as to have friends at a distance; they make the latitudes and longitudes.
Henry David Thoreau
Yeah I missed a few myself, should have grabbed a super blue before they became too expensive
The CO3 hunter in 440v/s60v started all the hub bub , and now the stretch doesn’t even look like
The OG stretch anymore
Glad my uncle got the Gayle Bradly hunting knife back in the day
I fondly recall walking into Marburg sporting goods in 1993 to buy a pack Frame to go hunt moose in Alaska and seeing the spyderco knives and falling in love with the CO3 and clip it delica .
And I bought the delica and CO3 , uncle the GB1
CO3 evolved in to the stretch then stretch 2 compulsion ( spyderco compulsion)
Proverbs 21:19 says, "It is better to live in a desert land than with a quarrelsome and fretful woman."
VG-10 is capable/fact to make 1000 cuts of 1/2" sisal rope while edge still slices phonebook paper w/o skid or tear.
My current EDC: laminated vg-10, ffg, 62rc +-0.5, 13dps, 0.009" BTE
I've been a constant fan of VG-10 ever since I got my first Spyder with that steel around 2001-02 or thereabout. In no way do I rank it among the current menu of Supersteels that we have been blessed with in the past 10 years or so. But I do consider VG-10 to be a really dependable workhorse blade steel that does hold up to hard use.
And I hope that unless Spyderco can find something in that performance range that proves significantly better I do hope that they continue to use it on their more common "user" models. VG-10 actually can take on a really nice edge for outdoor type chores like hunting, fishing ect.
VG-10 is capable/fact to make 1000 cuts of 1/2" sisal rope while edge still slices phonebook paper w/o skid or tear.
My current EDC: laminated vg-10, ffg, 62rc +-0.5, 13dps, 0.009" BTE
Holy Cow! 1000 cuts of 1/2" sisal rope with VG10 is a mind blowing result
It looks like I need to reprofile the edge of my Stretch 2 Lightweight to 13dps
I have pretty much finished my testing on the Stretch 2 Lightweight in VG10 and put all the film together on this film for my Youtube channel.
I conclude that this particular specimen of VG10 on this Stretch 2 LW just does not perform as well as it should.
I understand that I cant really compare the Stretch 2 LW and the Spyderco Astute directly because of differences in geometry, but I just do not believe that the Astute in 8cr13mov should perform 3 times as well as the Stretch VG10. Geometry absolutely counts, but the differences in behind the edge thickness between the two is negligible and should not account for nearly a 3 times difference in amount of processed sisal rope.
I realize that if I were to continue testing it I likely would continue to get better results with it progressively, but I have kinda had enough of it. Id like to move on to the next test subject.
I agree that geometry is a hard pill to swallow, especially to explain a 3-fold difference. However, think about how much that margin of difference shrank when changing the geometry to a more acute angle, and following some of the sharpening advice here.
I think it can be really surprising and difficult to truly appreciate how much of a difference edge geometry makes. Have you had a chance to check our Larrin Thomas's "regression formula" he put together where he can predict the CATRA scores?
Quick explanation in case you're unaware: The chemical names represent the different carbides that will form in the presence of a different carbide former. CrC are chromium carbides that form in the presence of chromium obviously. However, things like MC and MC6 are a bit different and depend on the presence and availability of vanadium, molybdenum and tungsten--if I remember right. He explains it a lot better on his blog.
If you dig around his blog, you can find the different carbide percentages for different steels and use that formula to find predictive CATRA scores that are based on his data. There's this chart with the different carbide percentages for many steels, but unfortunately not VG10. However it does have N690, and they're very similar at least content wise, so we could probably count on the percentage of chromium carbides to be even.
So you could shorten that formula down to this for VG10: TCC (mm) = -157 + 15.8*Hardness (Rc) – 17.8*EdgeAngle(°) + 11.2*16
Play around with the numbers and you should see how even small differences in edge angle result in large differences in the end result. It should also show how it makes a bigger difference than hardness too. In fact, according to Larrin and his data, the edge angle controls for larger differences than any other factor.
A member here named Deadboxhero (aka Triple B) put together this video using a spreadsheet to illustrate this really well too.
That's all relative to the blade blanks that Larrin constructed for the tests too, which is huge because that means it's only showing how edge geometry affects it. You then have to think of how the blade geometry affects the edge geometry. I'm going to borrow again from Larrin's work...
So I like this diagram a lot for many different reasons, but one especially is that it really shows that edge and blade geometry are two different things. Because that diagram can explain any V-bevel edge, but you can't really get an idea of what type of blade geometry it sits on right? Usually when people talk about the thickness behind the edge they mean the dimension in that diagram labeled 'd', but I mean just think about how different things can be with the same figure for 'd' but if the blade is 1 inch or 3 inch tall if it's 1/4" or 1/16" thick, if it's hollow ground, flat ground, zero ground, etc.
So think about that and the non-intuitive result you got from reducing the angle "only" two degrees. The thing is, how large 'b' and 'b' ' are is directly proportional to how large 'd' is, so it only "seems" intuitive that a 2 degree change wouldn't affect things that much, but the truth is that these variables are so tightly interdependent that you can't actually properly inuit how much change a specific angle will cause. It's sort of like trying to predict the most amount of outcomes, with the least amount of data. A human brain can't inuit such complex relationships, we have to actually calculate them.
That's really problematic because, honestly, most metrics for that data point aren't even super precise or accurate. I mean, such calculations should be considering sub-degree measures of the angle (minutes, seconds, or just rations), but most methods we have to actually measure/control for angle are not even accurate enough to facilitate that. For example, laser goniometers that are used to measure angles don't even have tolerances smaller than +/- 2 degrees, so it's very difficult to actually say one can measure an angle that accurately even with specialized tools--whether your system can hold an angle to tighter tolerances is another matter, but you definitely can't prove that it can with the tools available to consumers. Then, you as a sharpener also have to keep in mind how things like the difference in primary blade grind angle might need to be taken into account depending on what jig and system you're using. For example, the primary blade grind on a Manix 2 is 2.4 degrees. If you have a blade that is 4 degrees, and you don't take that difference into account then your data will reflect the difference that extra 2.4 degrees would make, and as we can see that could be quite substantial.
Anyway, hopefully that doesn't come off as condescending or as if I fancy myself some kind of expert, I just recently did a deep dive into this topic. Actually, reading the thread and watching the video, your results weren't that hard to believe at all for me, but I would have had the same intuition that a 2 degrees difference shouldn't be able to account for that before learning all those things.
I agree that geometry is a hard pill to swallow, especially to explain a 3-fold difference. However, think about how much that margin of difference shrank when changing the geometry to a more acute angle, and following some of the sharpening advice here.
I think it can be really surprising and difficult to truly appreciate how much of a difference edge geometry makes. Have you had a chance to check our Larrin Thomas's "regression formula" he put together where he can predict the CATRA scores?
Quick explanation in case you're unaware: The chemical names represent the different carbides that will form in the presence of a different carbide former. CrC are chromium carbides that form in the presence of chromium obviously. However, things like MC and MC6 are a bit different and depend on the presence and availability of vanadium, molybdenum and tungsten--if I remember right. He explains it a lot better on his blog.
If you dig around his blog, you can find the different carbide percentages for different steels and use that formula to find predictive CATRA scores that are based on his data. There's this chart with the different carbide percentages for many steels, but unfortunately not VG10. However it does have N690, and they're very similar at least content wise, so we could probably count on the percentage of chromium carbides to be even.
So you could shorten that formula down to this for VG10: TCC (mm) = -157 + 15.8*Hardness (Rc) – 17.8*EdgeAngle(°) + 11.2*16
Play around with the numbers and you should see how even small differences in edge angle result in large differences in the end result. It should also show how it makes a bigger difference than hardness too. In fact, according to Larrin and his data, the edge angle controls for larger differences than any other factor.
A member here named Deadboxhero (aka Triple B) put together this video using a spreadsheet to illustrate this really well too.
That's all relative to the blade blanks that Larrin constructed for the tests too, which is huge because that means it's only showing how edge geometry affects it. You then have to think of how the blade geometry affects the edge geometry. I'm going to borrow again from Larrin's work...
So I like this diagram a lot for many different reasons, but one especially is that it really shows that edge and blade geometry are two different things. Because that diagram can explain any V-bevel edge, but you can't really get an idea of what type of blade geometry it sits on right? Usually when people talk about the thickness behind the edge they mean the dimension in that diagram labeled 'd', but I mean just think about how different things can be with the same figure for 'd' but if the blade is 1 inch or 3 inch tall if it's 1/4" or 1/16" thick, if it's hollow ground, flat ground, zero ground, etc.
So think about that and the non-intuitive result you got from reducing the angle "only" two degrees. The thing is, how large 'b' and 'b' ' are is directly proportional to how large 'd' is, so it only "seems" intuitive that a 2 degree change wouldn't affect things that much, but the truth is that these variables are so tightly interdependent that you can't actually properly inuit how much change a specific angle will cause. It's sort of like trying to predict the most amount of outcomes, with the least amount of data. A human brain can't inuit such complex relationships, we have to actually calculate them.
That's really problematic because, honestly, most metrics for that data point aren't even super precise or accurate. I mean, such calculations should be considering sub-degree measures of the angle (minutes, seconds, or just rations), but most methods we have to actually measure/control for angle are not even accurate enough to facilitate that. For example, laser goniometers that are used to measure angles don't even have tolerances smaller than +/- 2 degrees, so it's very difficult to actually say one can measure an angle that accurately even with specialized tools--whether your system can hold an angle to tighter tolerances is another matter, but you definitely can't prove that it can with the tools available to consumers. Then, you as a sharpener also have to keep in mind how things like the difference in primary blade grind angle might need to be taken into account depending on what jig and system you're using. For example, the primary blade grind on a Manix 2 is 2.4 degrees. If you have a blade that is 4 degrees, and you don't take that difference into account then your data will reflect the difference that extra 2.4 degrees would make, and as we can see that could be quite substantial.
Anyway, hopefully that doesn't come off as condescending or as if I fancy myself some kind of expert, I just recently did a deep dive into this topic. Actually, reading the thread and watching the video, your results weren't that hard to believe at all for me, but I would have had the same intuition that a 2 degrees difference shouldn't be able to account for that before learning all those things.
Great post. There’s a lot to unpack there, but the information is really accurate as far as I can tell.
I agree that geometry is a hard pill to swallow, especially to explain a 3-fold difference. However, think about how much that margin of difference shrank when changing the geometry to a more acute angle, and following some of the sharpening advice here.
I think it can be really surprising and difficult to truly appreciate how much of a difference edge geometry makes. Have you had a chance to check our Larrin Thomas's "regression formula" he put together where he can predict the CATRA scores?
Quick explanation in case you're unaware: The chemical names represent the different carbides that will form in the presence of a different carbide former. CrC are chromium carbides that form in the presence of chromium obviously. However, things like MC and MC6 are a bit different and depend on the presence and availability of vanadium, molybdenum and tungsten--if I remember right. He explains it a lot better on his blog.
If you dig around his blog, you can find the different carbide percentages for different steels and use that formula to find predictive CATRA scores that are based on his data. There's this chart with the different carbide percentages for many steels, but unfortunately not VG10. However it does have N690, and they're very similar at least content wise, so we could probably count on the percentage of chromium carbides to be even.
So you could shorten that formula down to this for VG10: TCC (mm) = -157 + 15.8*Hardness (Rc) – 17.8*EdgeAngle(°) + 11.2*16
Play around with the numbers and you should see how even small differences in edge angle result in large differences in the end result. It should also show how it makes a bigger difference than hardness too. In fact, according to Larrin and his data, the edge angle controls for larger differences than any other factor.
A member here named Deadboxhero (aka Triple B) put together this video using a spreadsheet to illustrate this really well too.
That's all relative to the blade blanks that Larrin constructed for the tests too, which is huge because that means it's only showing how edge geometry affects it. You then have to think of how the blade geometry affects the edge geometry. I'm going to borrow again from Larrin's work...
So I like this diagram a lot for many different reasons, but one especially is that it really shows that edge and blade geometry are two different things. Because that diagram can explain any V-bevel edge, but you can't really get an idea of what type of blade geometry it sits on right? Usually when people talk about the thickness behind the edge they mean the dimension in that diagram labeled 'd', but I mean just think about how different things can be with the same figure for 'd' but if the blade is 1 inch or 3 inch tall if it's 1/4" or 1/16" thick, if it's hollow ground, flat ground, zero ground, etc.
So think about that and the non-intuitive result you got from reducing the angle "only" two degrees. The thing is, how large 'b' and 'b' ' are is directly proportional to how large 'd' is, so it only "seems" intuitive that a 2 degree change wouldn't affect things that much, but the truth is that these variables are so tightly interdependent that you can't actually properly inuit how much change a specific angle will cause. It's sort of like trying to predict the most amount of outcomes, with the least amount of data. A human brain can't inuit such complex relationships, we have to actually calculate them.
That's really problematic because, honestly, most metrics for that data point aren't even super precise or accurate. I mean, such calculations should be considering sub-degree measures of the angle (minutes, seconds, or just rations), but most methods we have to actually measure/control for angle are not even accurate enough to facilitate that. For example, laser goniometers that are used to measure angles don't even have tolerances smaller than +/- 2 degrees, so it's very difficult to actually say one can measure an angle that accurately even with specialized tools--whether your system can hold an angle to tighter tolerances is another matter, but you definitely can't prove that it can with the tools available to consumers. Then, you as a sharpener also have to keep in mind how things like the difference in primary blade grind angle might need to be taken into account depending on what jig and system you're using. For example, the primary blade grind on a Manix 2 is 2.4 degrees. If you have a blade that is 4 degrees, and you don't take that difference into account then your data will reflect the difference that extra 2.4 degrees would make, and as we can see that could be quite substantial.
Anyway, hopefully that doesn't come off as condescending or as if I fancy myself some kind of expert, I just recently did a deep dive into this topic. Actually, reading the thread and watching the video, your results weren't that hard to believe at all for me, but I would have had the same intuition that a 2 degrees difference shouldn't be able to account for that before learning all those things.
Hey thank you for the feedback! I dont take it as condescending at all. Im grateful that you watched my content.
One thing id like to clarify about my testing that I cant really be sure if I maybe misconstrued or omitted is that the edge angle for both the Astute and the Stretch 2 for the first sharpened test were at 18*DPS. The Astute cut the rope 280 times at 18*DPS and the Stretch cut the rope 80 times, then 100 times, then 125 times at 18*DPS. It wasnt until I changed the angle to 16*DPS that the Stretch 2 was able to cut 210 times. I think I understand that there are tons of variables that could cause differences in the actual angle that both of those knives end up with after sharpening, but id like to make it clear that what I am trying my best to test is how much sisal rope both of these knives (or any knife that I test) will cut with the same edge angle before it will no longer slice paper. I knew that the more acute the edge I put on the knife it would likely translate to more cutting performance in the test, what I didnt (and still dont) understand is why when I put the same edge angle (to the best of my ability) on the two knives why does the 8cr Astute perform more than 3 times as well at the first test of each.
I agree that geometry is a hard pill to swallow, especially to explain a 3-fold difference. However, think about how much that margin of difference shrank when changing the geometry to a more acute angle, and following some of the sharpening advice here.
I think it can be really surprising and difficult to truly appreciate how much of a difference edge geometry makes. Have you had a chance to check our Larrin Thomas's "regression formula" he put together where he can predict the CATRA scores?
Quick explanation in case you're unaware: The chemical names represent the different carbides that will form in the presence of a different carbide former. CrC are chromium carbides that form in the presence of chromium obviously. However, things like MC and MC6 are a bit different and depend on the presence and availability of vanadium, molybdenum and tungsten--if I remember right. He explains it a lot better on his blog.
If you dig around his blog, you can find the different carbide percentages for different steels and use that formula to find predictive CATRA scores that are based on his data. There's this chart with the different carbide percentages for many steels, but unfortunately not VG10. However it does have N690, and they're very similar at least content wise, so we could probably count on the percentage of chromium carbides to be even.
So you could shorten that formula down to this for VG10: TCC (mm) = -157 + 15.8*Hardness (Rc) – 17.8*EdgeAngle(°) + 11.2*16
Play around with the numbers and you should see how even small differences in edge angle result in large differences in the end result. It should also show how it makes a bigger difference than hardness too. In fact, according to Larrin and his data, the edge angle controls for larger differences than any other factor.
A member here named Deadboxhero (aka Triple B) put together this video using a spreadsheet to illustrate this really well too.
That's all relative to the blade blanks that Larrin constructed for the tests too, which is huge because that means it's only showing how edge geometry affects it. You then have to think of how the blade geometry affects the edge geometry. I'm going to borrow again from Larrin's work...
So I like this diagram a lot for many different reasons, but one especially is that it really shows that edge and blade geometry are two different things. Because that diagram can explain any V-bevel edge, but you can't really get an idea of what type of blade geometry it sits on right? Usually when people talk about the thickness behind the edge they mean the dimension in that diagram labeled 'd', but I mean just think about how different things can be with the same figure for 'd' but if the blade is 1 inch or 3 inch tall if it's 1/4" or 1/16" thick, if it's hollow ground, flat ground, zero ground, etc.
So think about that and the non-intuitive result you got from reducing the angle "only" two degrees. The thing is, how large 'b' and 'b' ' are is directly proportional to how large 'd' is, so it only "seems" intuitive that a 2 degree change wouldn't affect things that much, but the truth is that these variables are so tightly interdependent that you can't actually properly inuit how much change a specific angle will cause. It's sort of like trying to predict the most amount of outcomes, with the least amount of data. A human brain can't inuit such complex relationships, we have to actually calculate them.
That's really problematic because, honestly, most metrics for that data point aren't even super precise or accurate. I mean, such calculations should be considering sub-degree measures of the angle (minutes, seconds, or just rations), but most methods we have to actually measure/control for angle are not even accurate enough to facilitate that. For example, laser goniometers that are used to measure angles don't even have tolerances smaller than +/- 2 degrees, so it's very difficult to actually say one can measure an angle that accurately even with specialized tools--whether your system can hold an angle to tighter tolerances is another matter, but you definitely can't prove that it can with the tools available to consumers. Then, you as a sharpener also have to keep in mind how things like the difference in primary blade grind angle might need to be taken into account depending on what jig and system you're using. For example, the primary blade grind on a Manix 2 is 2.4 degrees. If you have a blade that is 4 degrees, and you don't take that difference into account then your data will reflect the difference that extra 2.4 degrees would make, and as we can see that could be quite substantial.
Anyway, hopefully that doesn't come off as condescending or as if I fancy myself some kind of expert, I just recently did a deep dive into this topic. Actually, reading the thread and watching the video, your results weren't that hard to believe at all for me, but I would have had the same intuition that a 2 degrees difference shouldn't be able to account for that before learning all those things.
Hey thank you for the feedback! I dont take it as condescending at all. Im grateful that you watched my content.
One thing id like to clarify about my testing that I cant really be sure if I maybe misconstrued or omitted is that the edge angle for both the Astute and the Stretch 2 for the first sharpened test were at 18*DPS. The Astute cut the rope 280 times at 18*DPS and the Stretch cut the rope 80 times, then 100 times, then 125 times at 18*DPS. It wasnt until I changed the angle to 16*DPS that the Stretch 2 was able to cut 210 times. I think I understand that there are tons of variables that could cause differences in the actual angle that both of those knives end up with after sharpening, but id like to make it clear that what I am trying my best to test is how much sisal rope both of these knives (or any knife that I test) will cut with the same edge angle before it will no longer slice paper. I knew that the more acute the edge I put on the knife it would likely translate to more cutting performance in the test, what I didnt (and still dont) understand is why when I put the same edge angle (to the best of my ability) on the two knives why does the 8cr Astute perform more than 3 times as well at the first test of each.
again, thank you my friend!
So to be clear, the best you were able to get with the Stretch at 18dps was 125 cuts, and then when you reduced it to 16dps it increased to 210?
Let's go back to that regression formula I mentioned before. The best I can tell, most VG-10 from Spyderco is ran at 58-59 HRC, so let's just assume 59 for a best case scenario, and then look at what Larrin's formula predicts for CATRA results...
According to Larrin's formula, you should expect to see a 22% increase in TCC on the CATRA test merely by reducing the edge angle by 2 degrees. Now, understandably, your increase of 125 at 18dps to 210 at 16dps is much more dramatic, but 22% is also not insignificant by any means. I don't think we can really compare the numbers or their percentile differences given the wildly different testing methodologies, mediums, etc. but it certainly supports the appearance of significantly increased performance with minimally reduced geometry, so it shouldn't be too surprising that a similar pattern appears in your own testing as you said you anticipated.
...what I didnt (and still dont) understand is why when I put the same edge angle (to the best of my ability) on the two knives why does the 8cr Astute perform more than 3 times as well at the first test of each.
Well, I may be inferring too much on my own here, but it sort of sounds like you're not actually appreciating the different between geometry as a concept, and a degree as a measure of angle as a component of geometry. One has to stay diligent in remembering that the measure of "18 degrees" actually expresses very little similarity in the absence of other information.
You know, a better way to think about this might be to think of a globe, and latitudinal and longitudinal coordinates. We're familiar with those coordinates as expressed in degrees, minutes and seconds. Those end up on a grid of course, but really what they're all expressing are angles of offset from the poles and the equator, right? Let's say...
39° 45' 19.9548'' N, 105° 13' 15.9600'' W (aka Golden, CO)
and
39° 44' 41.64" N, 104° 57' 52.20" W (aka Denver, CO)
Now, Denver and Golden are about 15-20 miles apart, and if you look at those coordinates they're pretty much 1 degree apart. Except, if you went further south, the difference of 1 degree would be much different than 15-20 miles. In fact at the greatest amount (at the equator) it would be more like 69 miles per degree.
Again, hopefully I don't come off as condescending describing grade-school geography and geometry, but I think it's important to bring it back to these basics because what's going on microscopically at the very apex of an edge is basically the same theoretically, but with some practical differences.
I'm going to use this diagram again...
What I like about it is that it has 'Sharpness / Edge Width' as b and then 'Theoretical Sharpness' as b'. That distinction is important, because no matter how much we may want it, at a microscopic level the bevel doesn't ever actually approach that perfect geometric triangle, but instead usually rounds off. That area is described by 'h', though it is sort of exaggerated in the diagram.
A great blog to really get an appreciation of how this all plays out on this microscopic level is Todd Simpson's "Science of Sharp".
Lots of images to showcase it, but let's just go with this one...
So check out the two lines marked Aa and Aa R1, and the line where they crossed marked V 1. Well, V 1 is essentially 'b' in our diagram. On that blade it measures 1.64 microns wide, and you can see where he's marked the vertical span of it measuring 3 microns as H 1. That mark where H 1 is at is basically the 'Theoretical Sharpness" in the diagram, as you can see even at that level that it degrades from a triangular shape into a rounded off shoulder.
Basically, even though the Stretch and the Astute were both at 18dps, meaning B was the same, d, b and b' were all larger on the Stretch. Except, while a difference in B of 1 degree might mean d only measures a few thousandths of an inch (.001") more or less, the difference in microns it makes at b is much more dramatic, and the difference in microns it makes at b' is much-much more dramatic. It's those dramatic differences--which are only recognizable at this microscopic scale--which translate into the dramatic differences you see in data set's like Larrin's and your own. Otherwise, if you compare them only with one data point like d you see what appears to be a small difference, and if only B no difference. You could have 18 for B for both, .004" versus .005" for d, 1 micron vs 3 micron for b and maybe 10 nanometers versus 50 for b'.
Here is another big thing to consider...
When you introduce the contact with a cutting board, the force of impact becomes a factor, meaning edge stability becomes more of a factor than it does in a CATRA test. Then, because all of those variables I mentioned previously also greatly affect edge stability, it makes it all that much more unpredictable. At that point, "dulling" may be more a manifestation of deformation than abrasion. Again, so far we're only talking about edge geometry, but the blade itself matters too because if what is above 'd' makes you bare down with more force, that means more impact force, which might lead to more dulling from impact than from wear.
Suppose that all of d, b and b' of the edge geometry were equal between the Stretch and the Astute by virtue of making B smaller on the Stretch--let's assume that is what you accomplished by making the Stretch 16dps and the Astute 18dps. Well, again, the edge is just slapped onto the blade, and that blade starts to get thicker on the Stretch at the point where 'd' is created by that edge, and it gets progressively thicker the further up the blade you measure laterally. For example, take a new measurement that we'll call 'e' and measure it .500" up the blade from the edge. Why .500"? Because that's the thickness of your rope, so that is the widest cross-section of the blade that is having to wedge through it.
"Dulling" as we perceive it is really just the result of the measure of b increasing. That happens through friction, where materials simply degrade the actual steel in that span of h where the theoretical sharpness exists, making it jagged, non-uniform, etc. That mechanism is known as abrasion, and the characteristic of steel to resist that abrasion is usually referred to as "wear resistance". However, the size of b can also increase through deformation, either through denting, rolling or chipping, and both on a microscopic or macroscopic level. Just like with "microchips", some dents and rolls can be so small that they only occur in that span defined by h that one can only see on a scanning-electron-microscope. Deformation that's at that scale is usually just considered to be the same as general wear, at least if one is trying to determine the "stability" of an edge, but that deformation is actually always happening, it's only whether it's happening to a perceptible level that changes.
So you very well could have got all of those other dimensions of the blade geometry equal by using unequal angles, but the difference in the rest of the blade almost undoubtedly meant more downward force being used, which means more impact force against the cutting board.
In fact, I think what might help is to flip this whole thing... What if it wasn't that the VG-10 performed so poorly on the Stretch, but that the 8cr on the Astute just performed extremely well? I think if you look around the depths of the Internet, you'll find there's actually a long tradition of thin, 8cr blades outperforming supposedly-better steels when the 8cr is more thinly ground than the comparison.
mcsquirgle - your knives instances test is fine and agreed, time to move on.
Mage7 - Excellent posts. For resolution, perhaps need to take an additional variable into account/analysis ...
'Gumminess' often associated with vg-10 knives. 1.5%Co plays important role/variable - choose the red pill = more fun. Commonly knife-used term 'ductile' is not interchangeable with 'gumminess'.
...In fact, according to Larrin and his data, the edge angle controls for larger differences than any other factor....
Maybe, but we don't know that from Larrin's regression formula, because I'm fairly certain Larrin published the unstandardized coefficients, not the standardized coefficients. That means that the formula "works" by plugging in parameters, but it doesn't give a view as to which variable has the largest effect, because each coefficient depends on its unit of measurement. (Standardized coefficients don't, which means you can compare the coefficients to each other.)
It may be that edge angle gives the largest effect of any in the formula; I'm just saying we can't determine that from unstandardized regression coefficients.
Steel novice who self-identifies as a steel expert. Proud M.N.O.S.D. member 0003. Spydie Steels: 4V, 15V, 20CV, AEB-L, AUS6, Cru-Wear, HAP40, K294, K390, M4, Magnacut, S110V, S30V, S35VN, S45VN, SPY27, SRS13, T15, VG10, XHP, ZWear, ZDP189
...In fact, according to Larrin and his data, the edge angle controls for larger differences than any other factor....
Maybe, but we don't know that from Larrin's regression formula, because I'm fairly certain Larrin published the unstandardized coefficients, not the standardized coefficients. That means that the formula "works" by plugging in parameters, but it doesn't give a view as to which variable has the largest effect, because each coefficient depends on its unit of measurement. (Standardized coefficients don't, which means you can compare the coefficients to each other.)
It may be that edge angle gives the largest effect of any in the formula; I'm just saying we can't determine that from unstandardized regression coefficients.
Well true and I don't mean to seem like I'm hanging everything on the regression formula, I just think it's one of the clearest and easiest ways to really get a grasp on how dramatically changing the angle can change things.
I suppose a much simpler way to say what I am trying to convey is that the difference between 1 and 2 degrees gets exponentially larger the smaller the scale it relates to.
I watched another video recently that gives a great practical demonstration with very little of these academics...
Basically, he shows how even an increase of 1 degree made the difference between an edge that had the strength to resist damage hammering through the nail and one that didn't.
mcsquirgle - your knives instances test is fine and agreed, time to move on.
Mage7 - Excellent posts. For resolution, perhaps need to take an additional variable into account/analysis ...
'Gumminess' often associated with vg-10 knives. 1.5%Co plays important role/variable - choose the red pill = more fun. Commonly knife-used term 'ductile' is not interchangeable with 'gumminess'.
Resolution! Thank you, that's the word/idea I have been trying to grab at this whole time and if was driving me nuts lol
Yeah, I agree. It's like trying to bake with a thermometer that only has three values: Too cold, just right and too hot. That's why we--consumers, average folks--use the Fahrenheit scale because it offer enough resolution for us to know which temperatures work best for cookies versus pizza. Then, of course, there's finer scales like the Kelvin scale that is more useful to scientific pursuits. (Well, I'm not sure science prefers the Kelvin scale for finer granularity as much as the way it incorporates the concept of absolute zero and all that, but I am really not smart enough to speak on any of that so just ignore that )
Just think... What if everyone could have a scanning electron microscope and whatever other fancy equipment would be needed to just measure parts of the edge in independent dimensional figures?
...In fact, according to Larrin and his data, the edge angle controls for larger differences than any other factor....
Maybe, but we don't know that from Larrin's regression formula, because I'm fairly certain Larrin published the unstandardized coefficients, not the standardized coefficients. That means that the formula "works" by plugging in parameters, but it doesn't give a view as to which variable has the largest effect, because each coefficient depends on its unit of measurement. (Standardized coefficients don't, which means you can compare the coefficients to each other.)
It may be that edge angle gives the largest effect of any in the formula; I'm just saying we can't determine that from unstandardized regression coefficients.
No, edge geometry is the biggest factor.
During the development of the AEB-L Mule team knife internal CATRA testing was done for QC and confirmation of hardness at the edge.
Edge geometry proved to be extremely important for TCC.
The data was also compared to Dr Larrin's CATRA regression to confirm the results and the data lined up beautifully.
A San Mai, SRS-13 Mule with unknown hardness was also tested as a control for the AEB-L since it has twice the M7C3 carbide volume. Well, the regression was accurate enough to solve for the missing hardness given the TCC at a specific edge angle with 12% M7C3 carbide volume lined up.
So the CATRA regression data was matched up with the experimental data showed that SRS-13 had a hardness of ~60 HRC
Incredible.
I didn't know the hardness of SRS-13 because it's San-Mai construction would require destructive testing to grind down to the layer where we could measure the hardness.
In the end, Dr Larrin's CATRA regression formula is useful for sandboxing differences between steels and edge geometry is the most significant factor just like in real world use.
It's such an important factor it's difficult to take a lot of testing we see seriously if they don't control for that variable.
Shawn/BBB - I concurred that edge geometry is the biggest factor in CATRA testing. However one should refrain from extrapolate TCC to rope cutting performance, although edge geometry is still important but it is just among important factors: edge profile; stiffness; pressure; cutting angle and against backing material+surface+impact.
Low psi(edge against material) in CATRA = more TCC, thus edge angle is biggest factor. Where low psi in RC (rope cutting) can be a liability in impact with backing while still only 1 rope cut per load, e.g. OP cross grain cutting board where surface has many groove lines. CATRA load is fixed, where manual load is high and increasing which lead to higher backing impact&abrasion, thereby this impact&abrasion becoming important factor.
I use 'stiffness' rather than 'hardness' because stiffness is deflection strength, where hardness is displacement strength/resistance. e.g. at same hrc, steel with higher RA% is less stiff (i.e. mushy). Stiff edge is highly important in impact cutting (rope cutting = compress+friction+impact+lateral[entry+exit backing]). Maybe Larrin should consider to include RA% in his TCC formula.
Edge profile for CATRA is flat/wharncliffe, most knives blade mostly has curvature. OP use belly part of the blade in this test, wear isn't uniform and impact can be bad especially deflected by grooves on cutting board.
I was afraid people would misunderstand my post. I didn't say edge geometry wasn't the biggest factor. In fact I specifically caveated that. Go back and read my post. I said that the formula does not give us the information about which variable is the biggest factor, if it is using unstandardized coefficients, because you can't compare unstandardized coefficients.
My comment was about what you can or can't deduce from a regression formula using Bs instead of Betas. Yours is about the importance of edge geometry. So we are not having a discussion about the same topic. I think everyone on this forum knows how important edge angles are.
It would be nice if Larrin would publish the formula with standardized coefficients. Then you could actually say something like "Edge angle is X times as influential as hardness" or whatever.
Steel novice who self-identifies as a steel expert. Proud M.N.O.S.D. member 0003. Spydie Steels: 4V, 15V, 20CV, AEB-L, AUS6, Cru-Wear, HAP40, K294, K390, M4, Magnacut, S110V, S30V, S35VN, S45VN, SPY27, SRS13, T15, VG10, XHP, ZWear, ZDP189
I was able to use surface ground to 3mm....ATS34, VG10, N690, D2, O1, 12C27, White Paper Steel, 1095, W2, A2, M340, 420 and AEB-L all ground at the same geometry, and all at the recommended HT for maximum wear resistance for each steel.
All sharpened on a 400 grit water stone.
The medium was 13mm hemp rope, and the cutting stopped when the edge would not cleanly cut a Yellow Pages piece of paper.
An industrial scale by Wedderburn was used to get the right amount of pressure, but open to slight moments of lapse.
The results could have been done by Larrin, as they lined up the same as his various charts.
Not exactly scientific I know, but I shared my results with Cliff Stamp. and he agreed that the geometry was the key in my testing.
Not a super steel, but VG10 is still my favourite, followed by AEB-L.
I only have five Stretch models and only could find a frn in black . Could it possibly be the CF model in ZDP189 ? Posted old shot so you could see texture . Dan
STRETCH 2 XL CPM CRUWEAR 
knives instances test is fine and agreed, time to move on.
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