Steel Edge Retention testing

[bladefan]

you could always try cutting used carpet... that seems to dull edges real quick!

 

[Cobalt]

you could always try cutting used carpet... that seems to dull edges real quick!

Yes, but it has to much other debri in it to be consistent for comparison purposes.:thumbdn:

Read Cliffs tests using carpet.

also if the below from Hob is correct, then this thread cutting test although cool is not so informative until you have gotten out to several thousand cuts for many of the better steels, because of the fact the difference in sharpenss between 40-50-60-70, etc, is nothing.

HH: Perhaps some don't also realize how crazy sharp 30-40g really is.

Nozh: I do not think that it is correct to say that 50g edge "twice sharper" then 100g edge.

For sharpness, value of absolute sharpness is practically not really possible to define, as towards 0g the scale would get hopelessly nonlinear, but in principle, it would be possible to use 0g as point of reference. Far more practical is it to use absolute bluntness as reference. My guess is that the thread, that Vassili is using, breaks at about 1.5kg (this corresponds to the strength of the polythread that I started testing on) on a completely unsharpened edge. So 30g is actually 2% bluntness while 40g represents 2.7% bluntness. This is a much more illustrative number, as shows, that both are bloody damn sharp with little difference between them. Now, after so-and-so many cuts the 30g blade dulls to 120g while the 40g blade dulls to 100g, or 8% and 6.7% of complete bluntness. So the first dulled by 6% while the second dulled by 4%....[B]a difference of wopping 2%[/B]!!!!!

).

 

[Troop]

Good job, Vassili. :thumbup: Thanks for all your hard work.

 

[HoB]

also if the below from Hob is correct, then this thread cutting test although cool is not so informative until you have gotten out to several thousand cuts for many of the better steels, because of the fact the difference in sharpenss between 40-50-60-70, etc, is nothing.

Not that I am necessarily right, but yes, that's what I meant. Well, maybe not several thousand but a lot. You can see in Vassili's data that at 240 cuts all three blades are pretty much in the same ballpark. At 700 cut though there is clearly a significant difference between the INFI and the FF in comparison with the 420. This is why the suggestions of more abrasive media. But I totally agree with you and others, it completely changes the test. I mean, in the extreme you could cut drywall as abrasive media, but I think you would see a completely different dulling behavior. The only exception is if you are only interested in the loss of the super sharpness in the beginning. You see in that the super sharpness is lost pretty quickly on all blades.

 

[Cobalt]

Not that I am necessarily right, but yes, that's what I meant. Well, maybe not several thousand but a lot. You can see in Vassili's data that at 240 cuts all three blades are pretty much in the same ballpark. At 700 cut though there is clearly a significant difference between the INFI and the FF in comparison with the 420. This is why the suggestions of more abrasive media. But I totally agree with you and others, it completely changes the test. I mean, in the extreme you could cut drywall as abrasive media, but I think you would see a completely different dulling behavior. The only exception is if you are only interested in the loss of the super sharpness in the beginning. You see in that the super sharpness is lost pretty quickly on all blades.

Well, we know that carpet is not a consistent media. Manilla rope does not offer enough resistance. However, the nice thing about the rope is that due to it's ease of cutting, it removes edge geometry for the most part as a factor and it also removes edge grit, for the most part as a factor. Not sure what other media might do this, without breaking the bank in cost.


it would be interesting to try this test with different blade/edge geometries. Eventually, edge geometry should take over though and a hollow ground knife might end up being the better cutter over flat or sabre/flat grind when the same steel is used.

 

[db]

I believe with rope cutting the blade grind is/can be a non factor if you do your cutting right at the end of the rope. The rope fibers fall away as they are cut and never really touch the blade grind. Nozh thanks for all the info your providing.

 

[nozh2002]

It may be different story after thousands cuts but I doubt that anybody have such workload on their knife for reasonable time. May be some professional manila rope cutters or something.

Of course we can continue to extreme, but I do not see this really practical.

I think that practical load will be somewhere before 400. Also most will not be able to sharpen it to same extent I did for this testing.

To me it is clear that FFD2 is better then INFI all over testing. I may understand that this is ground-shaking for some, but this is not the reason to go beyond reasonable load. I do not have any problem with the fact that INFI is not the best of the best. Why should it?

After thinking about this abrasive thing - I do not think that adding abrasive will show anything. Because if you exclude rope it will be pure abrasive against blade.

Load = Rope + Abrasive

Different steel will stay differently against Rope due to composition and hardness and natural properties of the steel, but all steel will stay same against abrasive. So it is like after cutting clean rope I will dull knife a little with wet stone. In result different aspects of impact rope cause to blade will be just jammed with big impact from abrasive which will be same for all steel (I am talking abut real natural abrasive - Sand (SiliconOxide)).

It will for sure brings us to the end of testing faster but results will not be clean and precise at it is for clean rope.

More dense material like wood or paper or MDF or some plastic looks better because they do not have abrasive which is harder then steel.

Thanks, Vassili.

 

[marthinus]

Sorry if this was asked before im falling asleep. What is INFI?

 

[HoB]

The proprietary knife steel of Busse knives. It is not a stainless steel but isn't very prone to corrosion, it holds an edge clearly for a long time, but most importantly it is rather tough.

 

[Cobalt]

I believe with rope cutting the blade grind is/can be a non factor if you do your cutting right at the end of the rope. The rope fibers fall away as they are cut and never really touch the blade grind. Nozh thanks for all the info your providing.

Interesting. and does make sense. would be interesting to verify..

Really at this poit I don't know of anything else that gives consistent data.

So ffd2 gives performance comparable to cpm10V or better maybe.

 

[Larrin]

So ffd2 gives performance comparable to cpm10V or better maybe.

Well if you believe Wayne Goddard (knifemaker, writer, one of the main users of rope cutting for testing), FFD2 does outcut 10V...

 

[nozh2002]

If you notice >$20 Laury PT blade doing pretty close to FFD2 so far and it has 63HRC on the edge. So I will not be surprized if ZDP or SGPS will do similar to FFD2 with their 65HRC.

I think ZDP, SGPS, Duratech and CPM 10V or CPM S90V are real competitors to FFD2. I'll take small break and will continue with one of this.

Thanks, Vassili.

 

[HoB]

Well, looks like hardness and toughness are really the important factors for ropecutting. Not too surprising, since it would mean that deformation is the leading dulling factor.

 

[nozh2002]

This is Lauri Progressive Tempered blade:

Thanks, Vassili.

 

[sodak]

Vassili,

If you need a 10V at 64.5 HRC knife to test, let me know. I'll loan you one.

 

[Cobalt]

Well, looks like hardness and toughness are really the important factors for ropecutting. Not too surprising, since it would mean that deformation is the leading dulling factor.

I would agree about hardness, but toughness, I am not so sure. S7 is way beyond most steels in toughness and yet it does not hold an edge anywhere near as long as other steels, like D2, A2, 30V, etc. L6 is another example of this. Extreme toughness but low edge holding.

 

[db]

I wouldn't count on hard L6 as having low edge holding if I was you.

 

[HoB]

I would agree about hardness, but toughness, I am not so sure. S7 is way beyond most steels in toughness and yet it does not hold an edge anywhere near as long as other steels, like D2, A2, 30V, etc. L6 is another example of this. Extreme toughness but low edge holding.

Good point. Unfortunately I don't have any experience with S7. I only know the testing numbers and usually edgeholding is measured on CATRA which uses a very abrasive medium so low edgeholding for S7 in those tests is no surprise and I don't have any personal experience. But my thinking was more along the lines, that on ropecutting you can never really eliminate some lateral force when the blade turns in your hand. I am sure Vassili's hurting wrist speaks volumes. So I would think an edge that is only hard but has very little toughness wouldn't last too long either, because it would chip out. So I would guess a hard edge with sufficient toughness would win out. Maybe this is part of the reason why the INFI blade fairs so well? But these were really only musings.

 

[Cobalt]

Good point. Unfortunately I don't have any experience with S7. I only know the testing numbers and usually edgeholding is measured on CATRA which uses a very abrasive medium so low edgeholding for S7 in those tests is no surprise and I don't have any personal experience. But my thinking was more along the lines, that on ropecutting you can never really eliminate some lateral force when the blade turns in your hand. I am sure Vassili's hurting wrist speaks volumes. So I would think an edge that is only hard but has very little toughness wouldn't last too long either, because it would chip out. So I would guess a hard edge with sufficient toughness would win out. Maybe this is part of the reason why the INFI blade fairs so well? But these were really only musings.

The high allow gives it wear resistance and this may account for what appears to be toughness, but is in fact more of a wear resistance.

 

[nozh2002]

I think I have almost all super steels - CPM 10V 63-63HRC by J.P.Holmes:

I also have SRS77 (which is Busse's S7).

I have bulat (wootz):

I have a lot of fun coming, I just need some little time to rest...
Only think I do not have is YXR7 (Roakstead) and Boker Markus Balbach Leo III Damascus.

Thanks, Vassili.