8Cr13MoV vs. S30V

[me2]

A while back I posted about a Griptillian in S30V and a Cara Cara in 8Cr13MoV not having enough difference to notice in my testing. I dug out the old test data and thought I'd share it here. I no longer have the Cara Cara, but I plan on running the test again with some 425 Modified steel from an old Buck.

Anyway, both blades sharpened on the 220/1000 grit water stone and microbeveled on the Sharpmaker. The initial sharpness was tested using thread cutting on a scale and the blades were within 10 grams of each other. After each had cut about 40 feet of cardboard, the force to cut the thread was the basically the same, with each trading back and forth on which one was sharpest. Both blades would still catch arm hair above the skin, and both would still cut hair off the back of my head well above my scalp.

I may have time to rerun the test with 425 Modified this weekend. If so, I'll post Monday.

[sal]

CATRA testing does consistently show the S30V to be a better edge holder by 60-80% than 8Cr as we've been using it. We believe our heat treat is optimal for both materials.

sal

[me2]

For the edge holding tests I do on my knives, I tend to focus on the very high range of sharpness. On a CATRA plot, this would be in the nearly linear portion of the first of the graph, before curve levels off. When the curve starts to level off is when I tend to sharpen the knives. For this reason, I have typically not found an advantage for the high wear steels. The best knives I've tested were the hardest, though they also had high wear resistance. Is there any CATRA data/plots available for these two steels as they are processed by Spyderco/Byrd?

[Cliff Stamp]

For this reason, I have typically not found an advantage for the high wear steels.

Mainly as you are using high/coarse carbide high wear steels, see if you can try something similar to F1 at 67 HRC and run the angle at about 5 dps, you also need to raise the polish as well as 1000 grit is a bit too coarse so initially all you will see is the breakdown of the scratch pattern which will not be reinforced so you might as well use 1095.

[Holland]

i watched jims test on the tenacious and what i got out of it was that 8Cr can take an amazing edge and hold it for an okay amount of time, but what separates it and s30v is the working edge. after s30v loses its hair whittling edge it has a good working edge, where as 8Cr seems to go from screaming sharp to dull.

im no expert though

[Cliff Stamp]

i...after s30v loses its hair whittling edge it has a good working edge, where as 8Cr seems to go from screaming sharp to dull.

They both have the same pattern of blunting curves, 8Cr13MoV will have the same extreme tailing effect.

The difference in these steels would be very difficult to detect without a very careful comparison where you could measure the sharpness to a precision of at least 5%. In fact even a minor difference in edge angle, grit finish, or quality of sharpening, or materials variance would be larger than the steel.



That is an 8Cr13MoV knife :



The knife is at about 5% of optimal sharpness there, if I cut all that cardboard again it would be about 3-4% of optimal, that is how slow the blunting continues at that point and this happens with all steels it is basic physics and has to do with the fact that the rate of blunting happens inversely proportional to the extend of blunting.

[Jurphaas]

Cliff, you amaze me time after time... fantastic how you master this topic of steel....
Jurphaas :)

[me2]

Any chance that knife can still slice paper? :)

[Cliff Stamp]

Any chance that knife can still slice paper? :)

Newsprint will catch unless you "fake it" by putting the paper under high tension, slice with a very long draw, enter on an angle (both ways), and slice almost parallel to the grain very quickly. Photocopy paper, no problem.

[anagarika]

Cliff, have you chanced to test other brand's 8Cr?

A YT I saw (ruslankiyasov) showed a tenacious that still slice copier paper after 70 or so cutting rope, while an Enlan EL02 not able to do the same after merely 30 cuts. Both are 8Cr13MoV. I think slicing paper has more to do with actual apex sharpness than geometry, but I might be wrong.

[Cliff Stamp]

Cliff, have you chanced to test other brand's 8Cr?

Yes, Byrd and Sanrenmu, looked at over a variety of materials, cardboard, rope, plastics and light metals, no significant difference (multiple samples of each).

However it does not surprise me that in general people would see a large difference between Spyderco and other brands due to the extreme difference in initial sharpness between Spyderco and other brands with Spyderco consistently coming initially far sharper with less damage. It is frequently the case that production (and even custom) knives can come with extreme over buffed/stropped edges which are severely weakened due to over heating and that in general it can take at least 3-5 sharpening sessions before the edge will stabilize. This also has to be actual sharpening, not stropping.

As an example, I recently did some work with a Mainstays Santoku, and the initial performance was less than 1/10 of the performance of the Spyderco K08 which has a similar steel. However after sharpening the Mainstays a half a dozen times the performance dramatically increased and it moved into the same class, though slightly behind which is where it would be expected to behave as it is likely a 3Cr13 class steel :



In general, you want to sharpen a knife at least a half a dozen times before you really pay any attention to the performance in regards to edge holding and durability as there are too many ways in which the edge can be damaged during the manufacturing of the knife. Usually if you pay attention carefully you can see a difference in how the edge forms in the sharpening as the extent of burr formation will be reduced as you move onto stable steel.

[Evil D]

This topic makes me laugh, because the only issue here is what we knife nuts consider "sharp". As Cliff clearly shows, that Chinese steel will cut just fine well beyond what most of our day to day EDC really needs, but in our minds that edge just isn't sharp anymore because we're accustomed to such higher levels of sharpness. Or at least that's how I look at it. Once a blade won't easily shave hair anymore, I consider it dull. Of course, work often demands that I keep using that "dull" edge since I can't just stop and sharpen my knife, so a steel that holds a good working edge for a good long time is important to me.

[chuck_roxas45]

This topic makes me laugh, because the only issue here is what we knife nuts consider "sharp". As Cliff clearly shows, that Chinese steel will cut just fine well beyond what most of our day to day EDC really needs, but in our minds that edge just isn't sharp anymore because we're accustomed to such higher levels of sharpness. Or at least that's how I look at it. Once a blade won't easily shave hair anymore, I consider it dull. Of course, work often demands that I keep using that "dull" edge since I can't just stop and sharpen my knife, so a steel that holds a good working edge for a good long time is important to me.

Very diplomatic and I agree with you. :D

[Cliff Stamp]

Once a blade won't easily shave hair anymore, I consider it dull.

That knife isn't actually dull at the end of that cutting as a general point, it would easily do most of the paper cutting tests that many people do on YT video's to show that a knife is sharp - it just is far sharper than that when it starts so even when it is 5% of optimal it is still 5x as sharp as many knives as-boxed.

Curiously enough, if you start wanting to keep your knives very sharp you will start to have very different impressions of what makes a "good" steel than common perception. For example if you want to keep a high sharpness then 420HC is a far better steel than ATS-34, 440A is much better than BG-42, AUS-6A is superior to S90V, etc. .

(assuming you are using knife like angles, not sharpening a knife like it is a cold chisel)

Of course you have to harden those steels sensibly, most of those steels can reach a far higher level of performance than what they are normally seen because what you get often has a high percentage of retained austenite, coarse primary aggregate, low carbon martensite, etc. because since the knives are cheap no effort is made to harden them.

When was the last time you used a 95% martensite 440A blade for example at 60/61 HRC which was oil hardened with deep cooling. Most perceptions of those steels are not actually on the steels but are just showing the effect of high temp, oil+cold vs low temp, air cooled + high temper. The second being very poor for knives.

Spyderco's 8Cr13Mov is a nice example of a fairly inexpensive knife given a decent hardening, as is the MBS-26 on the kitchen knives.

[Blerv]

If poorly executed/low hardness 420 is the reason for most the disappointed users, isn't that a relevant factor of the steel? If Mario Andretti owns a minivan I can still assume the average operator is of less skill than a more spry machine.

Is it not treated as such because it wouldn't make sense economically or because most choose to keep it merely as an economic trope?

As for 8Cr vs S30v it's never been much of a concern (just personally) as the models I prefer tend to only offer domestic of Japanese materials. Even if a Tenacious was the clear winner over s30v, give equal edges, I would gladly pick a Manix2 or Sage every time.

[Cliff Stamp]

Is it not treated as such because it wouldn't make sense economically ...

Knives with those steels are generally not promoted on performance hence little effort to optimize the steels. The actual behavior of the steels once properly hardened is in the same class as the well respected forged steels (1084, L6, 52100, etc.) in regards to ease of sharpening, obtainable sharpness, high sharpness edge holding, grindability, etc. . That is one of the most obvious examples how how bias/perception dominates forum perspective.

How can someone regard 1084 as an excellent knife steel but AUS-6A as being extremely poor when the carbon percentage in martensite, grain size, primary aggregate size/levels, etc. are all of the same class (as are the physical properties, wear resistance, etc.). But again most often you are seeing very poorly hardened low alloy stainless vs very well treated low alloy non-stainless and thus the distinction is in the heat treatment not the steel.

It would be similar for example to looking at flea market import lock backs vs Spyderco liner locks and then concluding that liner locks are stronger and more secure than lock backs. Of course what is really being shown by the data is that cheap flea market knives in general have weaker and less secure locks than high end production knife locks.

[Blerv]

I certainly would buy more AUS6 Seki knives if they made them. Seemingly (for whatever reason) VG10 has replaced the bulk of those steels for Spyderco. Prices seem more impacted by other factors so this likely a case of Constant Quality Improvement.

As David said my opinion of "dull" is not accurate by cutting test standards. I touch up quite a bit mostly due to boredom regardless of doing only a fair job :) . These low carbide steels are intriguing. I'm looking forward to some more Superblue in the future for the reasons you mentioned. :D

[Cliff Stamp]

I would like to see more similar steels, for example something similar to the A. G. Russell folding Honcho in CTS-BD1, soak at 2025F, oil quench, deep cool, double low temper, should be 95% martensite at about 0.55% carbon/solution and 60/61 HRC. Run the edge at < 0.010"/15 dps and you would have a very nice people friendly utility/edc knife which would be excellent in the kitchen, trivial to get sharp, stay very sharp well, excellent corrosion resistance (just under dishwasher safe). But that isn't a tactical/survival/bushcraft/super-steel current fad-tag designs so isn't market savvy.

[Chris_H]

Spyderco is supposed to be using CTS-BD1 in the next kitchen cutlery line-up. Perhaps they'll take your recipe suggestions, Cliff, and we'll get some interesting new cutlery to replace or compliment the aging Pro Culinaire knives in our kitchens.

[anagarika]

Cliff,

Thanks for explaining more. Slowly it starts making sense to me.