M390 vs. M4 Rope Cut Test

[JNewell]

Great writeup!

Does the rope used contain anything in it that is abrasive such as certain silicone particles? I am always impressed when I read about M390. It seems to perform well in virtually all conditions, and really leave everything in the dust when it comes to cutting objects that tend to be more abrasive, even when being compared to steels that are 5+ higher in Rockwell Hardness!

Any idea if the M4 Millie is from when Spyderco was supposedly hardening M4 slightly differently (IIRC, I read here earlier models were a little harder)

I just got a M390 blade I am going to EDC...hopefully it won't be too hard for me to sharpen!!!

I don't recall any confirmed report that Spyderco made a conscious decision to change the hardness for CPM-M4. The first run of Bradley folders were accidentally run at 64-65. There was discussion about subsequent production being run lower but it's never been confirmed one way or the other, as far as I know. One of the M4 Mules tested at 62.5. I don't have any test reports for the Military M4 blade at my fingertips but I think you can assume it's in the 62-63 range.

 

[Ankerson]

I always find these test interesting. Recently found this that I also found interesting showing a simple carbon steel with proper heat treat and geometry cutting rope.

First rope cut count is 150. Still shaves.

Bumps the rope up from 3/8 to 3/4.

Do 100 more cuts, not hair popping sharp, still shaves, no discernible dings. Not bad for a simple carbon steel that can still be stropped back to sharpness.

[video=youtube;cRjOtyqJ6P4]https://www.youtube.com/watch?v=cRjOtyqJ6P4[/video]

Doesn't mean anything, that's push cutting, not draw...

 

[Ankerson]

Does the Military not have a similar enough geometry? From your measurements, there is only a 0.005" - 002" difference in edge thickness with the Gerber being thicker, and the edge angle of the Gerber is larger. I'm not going to push that whatever Gerber used is better than S30V, but I will say I think rope cutting isn't sensitive enough to tell differences as reliably as was once thought.

Actual measures would have to be made on the actual knives used....

It's technique and the actual downforce needed....

 

[marthinus]

Doesn't mean anything, that's push cutting, not draw...

Still cuts the rope

 

[Ankerson]

Still cuts the rope

With almost zero wear on the edge compared to draw cutting that is much more abrasive to the edge...

That's a test some do to impress people as a stunt... And people who don't know any better go WOW....

While the rest of us laugh.....

 

[me2]

VB's tests don't measure down force, it's just an endurance test with a simple cut test to check for sharpness.

 

[marthinus]

With almost zero wear on the edge compared to draw cutting that is much more abrasive to the edge...

That's a test some do to impress people as a stunt... And people who don't know any better go WOW....

While the rest of us laugh.....

Shows you how good push cutting is to protect your edge from abrasive wear compared to draw cutting then.

 

[Ankerson]

VB's tests don't measure down force, it's just an endurance test with a simple cut test to check for sharpness.

Still takes a certain amount of downforce to get through the rope and that will increase as the knife dulls..

Also as the downforce increases so does the stress on the edge increasing edge wear.

That doesn't change..

 

[nccole]

Still takes a certain amount of downforce to get through the rope and that will increase as the knife dulls..

Also as the downforce increases so does the stress on the edge increasing edge wear.

That doesn't change..

Never really thought about that, but it makes sense. I don't ever recall anyone mentioning that before. Your rate of dulling is not linear. Could you take that further and make a general statement saying the steels that hold their finer edge longer have an advantage over steels that don't? I really like for a steel to keep the fine edge longer. It is more of a feel thing, I like the knife to feel effortless gliding through cardboard. I don't want it to get to that "good enough" stage quickly.

 

[Ankerson]

Never really thought about that, but it makes sense. I don't ever recall anyone mentioning that before. Your rate of dulling is not linear. Could you take that further and make a general statement saying the steels that hold their finer edge longer have an advantage over steels that don't? I really like for a steel to keep the fine edge longer. It is more of a feel thing, I like the knife to feel effortless gliding through cardboard. I don't want it to get to that "good enough" stage quickly.

Finer will be gone really fast when abrasive materials are cut so it's really more the steels with the higher carbide content and at higher hardness ranges that do better from what I have seen in my testing...

Like a steel that is still at 10 LBS of downforce while another might be 18 LBS in the same number of cuts.

Or as an example one HCV steel at 14 LBS @ 100 cuts while a lower carbide steel is at 17 LBS @ 100 cuts, both started at 11 LBS....

And 20 LBS and done at 160 cuts while the other one is still at 14 LBS at 160 cuts (HCV).... And still VERY sharp while the other one is to the point of being dull......

And that's PRODUCTION knives......

 

[Ankerson]

I didn't find it polite to call me out like that. You basically said my intellect cannot grasp what your tests are about. If somebody calls me out and basically calls me a retard i'm not just going to sit there and take it. You politely called me stupid. Therefor it didn't make me happy.It seemed also like your saying no one should be doing any testing on these steels cause you have more skills or knowledge or something and should leave it to the professionals. I believe Ankerson has tested all these steels already which makes the tests moot. See i can kinda talk all smart:foot:. Anyways hope there's no hard feelings,wish you well,and hope all your testing goes well too. I won't particate in anymore of your posts i worn out my welcome and i know it and honestly my knife knowledge is far less than anyone here so i'll just stay out of it. Sometimes stuff just rubs me the wrong way and i might have bi-polar or something so don't take it personally even though I'm pretty sure you were calling me an idiot and possibly trolling me. Anyways i dropped it and you won't here from me again. Wish you well.

I think it's a good thing to see more people actually doing some testing, the more information the better really.... :thumbup:

As long as the variables are reduced so they don't show bias it's all good..

Or don't alter the process to slant the results on how they want them to be...

 

[me2]

Never really thought about that, but it makes sense. I don't ever recall anyone mentioning that before. Your rate of dulling is not linear. Could you take that further and make a general statement saying the steels that hold their finer edge longer have an advantage over steels that don't? I really like for a steel to keep the fine edge longer. It is more of a feel thing, I like the knife to feel effortless gliding through cardboard. I don't want it to get to that "good enough" stage quickly.

This has been what I was interested in since I started messing around with knives. The tests I've done show more dependence on hardness/heat treatment and less on wear resistance. You'll note this is directly opposite of Ankerson's tests. For an idea of the kinds of steels that hold high sharpness, look into razor steels, mtrerials for microtome blades, etc.

Edited to add: steels used for fine finish cuts on wood are also good candidates.

 

[Vegas Blade]

I think it's a good thing to see more people actually doing some testing, the more information the better really.... :thumbup:

As long as the variables are reduced so they don't show bias it's all good..

Or don't alter the process to slant the results on how they want them to be...

Ankerson, I agree with that wholeheartedly. I really try to do that with my testing. I try to do the tests in such a way as to eliminate bias. I believe I was successful. Evidence of that was the fact that 1) I was very surprised by the results, not what I expected and 2) M4 is probably my favorite steel, so I had to ensure I didn't manipulate the test for M4 to "win" per se.

 

[Ankerson]

This has been what I was interested in since I started messing around with knives. The tests I've done show more dependence on hardness/heat treatment and less on wear resistance. You'll note this is directly opposite of Ankerson's tests. For an idea of the kinds of steels that hold high sharpness, look into razor steels, mtrerials for microtome blades, etc.

Edited to add: steels used for fine finish cuts on wood are also good candidates.

That's not the opposite of what I am doing, as they are all connected and the data is all there.

It's impossible not to have the data when the testing is being done.

In the end dull is freaking dull is freaking dull, there is no way around that....

Higher hardness is directly linked to higher compression strength that is directly linked to higher edge stability.

Now yes the carbide percentages do matter, too high there can be problems, too low and the blade goes dull too fast.

The reason why steels like Rex 121 that have extreme carbide volume don't actually do as well in knife blades with reasonable edge geometry as Steels like CPM 10V.

And Crucible said that also... And that's why they don't recommend REX 121 for knife blades as state that REX 121 won't offer anything over CPM 10V when used in knives.

But take REX 121 and use it for what it was designed for and it excels.

There is a limit to everything....

 

[chiral.grolim]

This has been what I was interested in since I started messing around with knives. The tests I've done show more dependence on hardness/heat treatment and less on wear resistance. You'll note this is directly opposite of Ankerson's tests. For an idea of the kinds of steels that hold high sharpness, look into razor steels, mtrerials for microtome blades, etc.

Edited to add: steels used for fine finish cuts on wood are also good candidates.

It's funny you should mention microtomes, as the best blades for those (one's able to consistently achieve the thinnest edges with highest durability for making consistent cuts thinner than 10um) are "pure carbide" - glass, TC, and diamond. The glass blades do need to be replaced more often due to fluidity (the edge deforms due to heat and gravity, etc.) but all of these materials achieve higher hardness than the steels, providing a stronger ultrathin-edge for non-abrasive cutting. HOWEVER they are NOT meant for abrasive or "heavy-handed" cutting as is being described here. That fine edge can be destroyed almost immediately by contact with a hard particle at too fast of a speed or that bends the edge slightly out of alignment, resulting in a fracture.


What is really needed here is a proper understanding of apex-diameter and how an increasing diameter affects the force required to complete a cut, and also (or more so) how steel type vs. edge geometry affects the rate of increase in apex-diameter as the edge degrades.

 

[Ankerson]

It's funny you should mention microtomes, as the best blades for those (one's able to consistently achieve the thinnest edges with highest durability for making consistent cuts thinner than 10um) are "pure carbide" - glass, TC, and diamond. The glass blades do need to be replaced more often due to fluidity (the edge deforms due to heat and gravity, etc.) but all of these materials achieve higher hardness than the steels, providing a stronger ultrathin-edge for non-abrasive cutting. HOWEVER they are NOT meant for abrasive or "heavy-handed" cutting as is being described here. That fine edge can be destroyed almost immediately by contact with a hard particle at too fast of a speed or that bends the edge slightly out of alignment, resulting in a fracture.


What is really needed here is a proper understanding of apex-diameter and how an increasing diameter affects the force required to complete a cut.

And that in effect is what some people do in testing on purpose to prove their theory..

They weaken the edge geometry to the point of failure on purpose to meet a predetermined agenda, or to put simply the variables are slanted on purpose to give one thing an advantage over the other by changing the variables until the results they want are met.

The results aren't wrong in that the theory is proven, but they are slanted to favor a predetermined result so they aren't exactly honest either.

That's the area that some scientists play in so people really have to be very careful when they read the results from whatever source and also why many scientific findings (results) have been overturned over the years.

They play with the fact that most people either don't know what they are looking at and or they don't care enough to really look at it and just take the results (Findings) at what they are blindly because they figure a Scientist did it so it has to be true and honest right.....

There is a very fine line between Right/Honest and Right/Dishonest..... One is agenda driven and the other one isn't... While both are scientifically correct.... And that's where the confusion comes in... And why it's really hard to argue against the agenda driven results...

What happens or what needs to happen is another Scientist has to be hired or be interested enough do actually do another study showing the bias of the prior study and have it reviewed. That's were politics comes in a lot of time based on the reputation of the 1st Scientist that did the initial study and who it was that backed them agenda based or not....... Like I said both studies are scientifically correct...... Not exactly an easy or fast process.....

 

[Ankerson]

Ankerson, I agree with that wholeheartedly. I really try to do that with my testing. I try to do the tests in such a way as to eliminate bias. I believe I was successful. Evidence of that was the fact that 1) I was very surprised by the results, not what I expected and 2) M4 is probably my favorite steel, so I had to ensure I didn't manipulate the test for M4 to "win" per se.

I could tell you how to change the variables so that M4 would win...

But then that would be both bias and the process that I pointed out in another point of predetermined results.... Agenda.......

That's why testing needs to honest, and the person doing the actual testing..

 

[me2]

Actual measures would have to be made on the actual knives used....

Note I did ask VB for those. He either doesn't want to provide it for whatever reason, or doesn't have the means to provide it. Not everybody has calipers laying around.

 

[me2]

Finer will be gone really fast when abrasive materials are cut so it's really more the steels with the higher carbide content and at higher hardness ranges that do better from what I have seen in my testing...

Like a steel that is still at 10 LBS of downforce while another might be 18 LBS in the same number of cuts.

Or as an example one HCV steel at 14 LBS @ 100 cuts while a lower carbide steel is at 17 LBS @ 100 cuts, both started at 11 LBS....

And 20 LBS and done at 160 cuts while the other one is still at 14 LBS at 160 cuts (HCV).... And still VERY sharp while the other one is to the point of being dull......

And that's PRODUCTION knives......

Are those actual numbers or examples? Which knives were used if it is the former?

 

[me2]

And that in effect is what some people do in testing on purpose to prove their theory..

They weaken the edge geometry to the point of failure on purpose to meet a predetermined agenda, or to put simply the variables are slanted on purpose to give one thing an advantage over the other by changing the variables until the results they want are met.

The results aren't wrong in that the theory is proven, but they are slanted to favor a predetermined result so they aren't exactly honest either.

That's the area that some scientists play in so people really have to be very careful when they read the results from whatever source and also why many scientific findings (results) have been overturned over the years.

They play with the fact that most people either don't know what they are looking at and or they don't care enough to really look at it and just take the results (Findings) at what they are blindly because they figure a Scientist did it so it has to be true and honest right.....

There is a very fine line between Right/Honest and Right/Dishonest..... One is agenda driven and the other one isn't... While both are scientifically correct.... And that's where the confusion comes in... And why it's really hard to argue against the agenda driven results...

What happens or what needs to happen is another Scientist has to be hired or be interested enough do actually do another study showing the bias of the prior study and have it reviewed. That's were politics comes in a lot of time based on the reputation of the 1st Scientist that did the initial study and who it was that backed them agenda based or not....... Like I said both studies are scientifically correct...... Not exactly an easy or fast process.....

Your insinuations of an agenda are misplaced. No one thinned anything to the point of failure. I took stock thickness production knives, rebeveled them to fit the Sharpmaker, sharpened them, repeated VB's tests, and found lower end steels could make the same number of cuts in rope and still slice paper as some upper end steels, even with thicker geometries. That's it. The answer to my question was yes, lower end steels can make the number of cuts VB posted and still pass the test of slicing paper. I haven't gone to 900 yet, but eventually I'll try it.