Multi-angle/steel edge retention comparison on 1/2 manilla h

[Cliff Stamp]

I have wanted to do this for a long time, however the sheer magnitude of the work involved kept me from committing to it until I worked some things out method and analysis wise because I did not want to get into it and have to start over. However as it is critical to the Mule-Library program I have started a test run which I will do on two Spyderco knives. The procedure is basically this :

-sharpen a knife on a Wicked Edge/1000 grit diamond with a specific angle micro-bevel
-cut 1/2" hemp and periodically measure the sharpness
-determine the edge retention statistics
-repeat a few runs until stable
-then repeat this whole thing across a range of micro-bevel angles
-then repeat this whole thing again across a range of steels
-he work is blinded to prevent bias

The results of this comparison when finished allow you to answer some very interesting questions such as :

-At what angle do I need to sharpen 420J2 to have the same edge retention as as 21 dps - 1000 grit WE edge on S110V cutting half inch manilla hemp?

This question in fact many people don't even realize has an answer at all. In fact the more dramatic question :

-At what angle do I need to sharpen 420J2 to have twice the edge retention as as 21 dps - 1000 grit WE edge on S110V cutting half inch manilla hemp?

also likely has an answer as well because the influence of edge angle on edge retention is very large.

Here is one run only on a VG-10 blade from Spyderco (Lum Chinese) :

-primary grind full zero
-edge bevel is approx. 6.5 dps in the final sweep (slop from stone wear, not intentional)




I would like to get 11 dps, but it is not possible easily with the WE, I am going to play with this a little. In fact very low angles would be interesting because at some point the strength would be compromised and the apex would fail by lack of strength. However hemp is so soft that this takes very low angles, less than 5 dps.

Now before anyone reaches any dramatic conclusions from the particular shapes or relationship between one angle and another, again this is one run only I can not even bound the performance with error bars at this point. However there are still some obvious observations :

-the edge retention appears to depend critically on the edge angle
-further it decreases significantly as the micro-bevel angle is increased
-this change is so large that angle could be as critical (or more) than the steels

A lot of this I have discussed before, however the point to this is to move from these general statements to doing the work in enough volume to allow answering some very specific questions about steels and angles and at what point one can compensate for another.

It will take 3-5 runs before the measurements will stabilize and I think it should be a smooth trend. That large difference between 13 and 15 dps is likely just amplified by random scatter. This is a lot of work, just to compare two steels will take about 100 runs of cutting hemp so do not expect it any time soon.

As a final caveat, you can not generalize from this to edge retention in general. Hemp is so weak (compressible) that it can easily be cut with ultra-low angles in contrast hard wood cutting (plywood etc.) can easily turn edges at 10 dps on weaker steels. Thus if you ask the same question :

-At what angle do I need to sharpen 420J2 to have twice the edge retention as as 21 dps - 1000 grit WE edge on S110V cutting half inch plywood?

The answer might be that it is not possible as you can not reduce the angle on the 420J2 enough to compensate as it would be so low it would not have the strength to cut the plywood and would just deform.

[tvenuto]

Thanks for doing this testing. A very informative discussion on one of the factors involved in the ever-debated topic of edge retention.

[Cliff Stamp]

I have done this in the past on isolated trials, but not something on this scale to allow anything beyond the generalizations of edge angle being critical and it is compromised severely at high angles. This is interesting to me as I am very curious about the levels of overlap. I am trying to decide now on which other Spyderco to use; 8Cr13MoV, S30V or the Farid collaboration in ultra-high carbide.

[Ankerson]

Cliff,

Good deal. :)

I did this awhile back at 10,15,18 and 20 DPS...

So it will be interesting to see what you come up with, although I think you already know what is going to happen. :)

Jim

[Cliff Stamp]

I know the general trends as I have done angle comparisons since 98' but not in enough volume to actually allow dependency calculation. This work will allow specific questions to be answered and if I expanded it over grits and then materials it could even answer questions such as :

-At what angle / grit finish does 8Cr13MoV slicing 1/2" Dyneema/Braid have 50% more edge retention than a 21 DP/1000 grit finish on S30V slicing 1/2" hemp ?

[Ankerson]

I know the general trends as I have done angle comparisons since 98' but not in enough volume to actually allow dependency calculation. This work will allow specific questions to be answered and if I expanded it over grits and then materials it could even answer questions such as :

-At what angle / grit finish does 8Cr13MoV slicing 1/2" Dyneema/Braid have 50% more edge retention than a 21 DP/1000 grit finish on S30V slicing 1/2" hemp ?

Are you going to factor in blade geometry as well?

I did that also.... As did some others.

[Gerard Breuker]

Love these threads but hate trying to put my nose into my screen.
Please make the results a bit easier to see by enlarging the results a little.

[Fancier]

Wouldn't increasing the size of the images on your computer screen help? Under Chrome it is as simple as holding down control and scrolling the size as desired.

[Cliff Stamp]

Are you going to factor in blade geometry as well?

This is mainly on edge retention as influenced by apex angle / steel, the knife is cutting ability optimized. I have looked at gross geometry as well and how it influences cutting ability and how that has spillover into edge retention. In this case the effect is minimized due to the way the hemp is cut so that the applied load doesn't directly translate to increased pressure on the apex itself.

Love these threads but hate trying to put my nose into my screen.

Interesting, that is PB converting the image which it does very horribly in this case from the uploaded original so it ends up very blurry. I think the problem is that the drawing is very wide because I put them side by side. When I update it I will just do it individually.

[Ankerson]

Are you going to factor in blade geometry as well?

This is mainly on edge retention as influenced by apex angle / steel, the knife is cutting ability optimized. I have looked at gross geometry as well and how it influences cutting ability and how that has spillover into edge retention. In this case the effect is minimized due to the way the hemp is cut so that the applied load doesn't directly translate to increased pressure on the apex itself.

OK, that's enough work in itself...

20 DPS and over really sucks cutting rope.... Unless the blade geometry is really thin....

I am guessing you are also using micro bevels?

[Cliff Stamp]

I suppose you are also using micro bevels?

Yes, that is what is being changed. I am currently running 13 to 25 dps in steps of 2 dps. The cutting ability is very high, the micro-bevel is too small to affect that, they all can cut 1/2" hemp with 4-5 lbs on a 2" draw, but the edge retention is compromised as the angle increases.

[Ankerson]

I suppose you are also using micro bevels?

Yes, that is what is being changed. I am currently running 13 to 25 dps in steps of 2 dps. The cutting ability is very high, the micro-bevel is too small to affect that, they all can cut 1/2" hemp with 4-5 lbs on a 2" draw, but the edge retention is compromised as the angle increases.

On 1/2" rope it won't be too bad..... If the geometry isn't thick....

On anything over 15 DPS I felt like I was wasting rope because the edge retention dropped so much... It was funny really..... Wasn't as bad with thin geometry around .005" as it was with the normal .025-.030....

10 DPS on thin geometry cuts really nice even on thicker rope, coarse edge even nicer.... :)

[Cliff Stamp]

Care is needed here as I am talking about edge retention, not cutting ability.

The cutting ability is greatly increased by many factors which will have little to no effect on the edge retention due to the way the hemp is being cut here. In general as long as the media isn't binding the effect will be low as there is no translation of loads to lateral forces on the edge. But as a general practice it has a large effect, often critical if it makes the cuts unstable.

As an obvious case which is easy to understand, watch someone try to cut a 2x4 with a blade that doesn't handle well. The knife is twisting/turning, etc. which is putting extremely high lateral forces across the edge. Now watch someone cut it with a decent knife and there are almost no lateral forces. Hence even things like grip stability have large effects on edge retention in a practical sense, especially with fillet knives due to bone contacts.

[Ankerson]

Care is needed here as I am talking about edge retention, not cutting ability.

The cutting ability is greatly increased by many factors which will have little to no effect on the edge retention due to the way the hemp is being cut here. In general as long as the media isn't binding the effect will be low as there is no translation of loads to lateral forces on the edge. But as a general practice it has a large effect, often critical if it makes the cuts unstable.

As an obvious case which is easy to understand, watch someone try to cut a 2x4 with a blade that doesn't handle well. The knife is twisting/turning, etc. which is putting extremely high lateral forces across the edge. Now watch someone cut it with a decent knife and there are almost no lateral forces. Hence even things like grip stability have large effects on edge retention in a practical sense, especially with fillet knives due to bone contacts.

I reduced the binding effects also... :)

All I can say is take your time and take it easy. :)

[Laethageal]

Thank you for yet another interesting testing. I'll be looking for updated results as you perform more runs!

On a completely different subject:

-At what angle / grit finish does 8Cr13MoV slicing 1/2" Dyneema/Braid have 50% more edge retention than a 21 DP/1000 grit finish on S30V slicing 1/2" hemp ?

I wish you have a really deep pocket if you do some much testing on edge retention cutting Dyneema rope like the AmSteel. Do you mind telling me how such rope resist cutting on sharp corners or blade if you did some testing on it? I planned on getting some but had no idea how well it resisted wear/cut and if it was worth the hefty price tag.

[Cliff Stamp]

I wish you have a really deep pocket if you do some much testing on edge retention cutting Dyneema rope like the AmSteel.

Ha, I think only David Boye actually buys that rope to cut up, it is crazy expensive. High end fishing/mooring lines like that can cost in excess of $15/ft. I actually live in a fishing community, I have just asked locals for used rope as it is replaced periodically. Because it can be massive, 1-2" thick, it doesn't take much of it to have a huge amount to cut up as you have to unbraid it and cut single strands unless you have a fairly large knife and even then, making a cut through a modern UHMW synthetic rope isn't trivial.

[Cliff Stamp]

Here is an update with two runs with the 13 dps micro-bevel angle to show the relatively high scatter at this point :



I also chopped the graphs apart to make them larger and easier to read after PB has recoded them. I suspect that by the time there are three runs with all of the angles then the dependency will be fairly clear. Even this though makes a point about expected differences. If you have to do very strict comparisons and average a number of times to map out the trend then an isolated 1 vs 1 trial isn't like to show it at all due to the random/systematic biases which can skew the results.

This is why often you see people on YT and elsewhere who get confused and argue that the kind of performance that graph describes doesn't happen and that there is the same edge retention at 25 dps as there is at 15 dps. They will then do some cutting and "prove" that, often right on video. This is however dealing with a very important question which is "Would I see this behavior in use when I am not counting/controlling cuts?" . The answer might simply be no unless you are looking at really long term results as that essentially does a type of averaging.

[Cliff Stamp]

Here is an update with most angles having two runs so you can see the scatter :



As an interesting point which raises a few questions, the difference in edge retention seen here from the lowest to highest angle (13 to 25 dps) is actually much larger than the difference seen in edge retention in Bohler's CATRA data if you go from the highest performance in M4/m390 down to 440C. In fact the difference due to the micro-bevel change is so large that it literally is the scale/magnitude as the size of change you see on CATRA comparisions if you jump from S90/ZDP/M4 right down to 420HC.

As an additional point, further consider that this range of angles isn't as far as you can go, I only stopped at 13 dps as it is a WE limitiation on the base setup, the performance continues to increase as the micro-bevel angle is dropped further. The same type of performance change is also seen if you change grits as well. Think about what this means in regards to edge retention in steels, in particular if steels with high apex stability can hold very low edge angles without suffering carbide tearout and how important in general steel is compared to edge angle/grit finish.

And, this is the critical part, such steels are often less expensive do you can grind them at those lower angles and risk the occasional hard contact damage as you are not that concerned about aggressive sharpening as you can "use up" the knife.

--

I will likely do three runs with each angle and then check it with another steel, I was thinking S30V but I might use the 10V/K2 either as the one I received has an edge thickness so low (0.010"-0.012") that is could fairly easily be reset to a low bevel without having to zero the full knife.

[Laethageal]

I will likely do three runs with each angle and then check it with another steel, I was thinking S30V but I might use the 10V/K2 either as the one I received has an edge thickness so low (0.010"-0.012") that is could fairly easily be reset to a low bevel without having to zero the full knife.

Can wait to receive mine next week and try it up. I thought it was thicker behind the edge. That's a good news for me.

[Cliff Stamp]

...

I thought it was thicker behind the edge.

There would be expected to be significant differences in production knives in that respect. It would only take one more pass on the belt to make this edge 50% thicker. I was somewhat surprised as the profile given the promotion as it isn't some kind of "heavy duty" knife like the Tuff, or this one isn't anyway, it is more of a precision cutting folder - more so than the as-stock Paramilitary I have for example.