New testing session.

[the possum]

Physicists, when they try to compare certain property of materials create equal testing conditions, which you do not. Blade thickness, geometry and initial edge sharpness vary wildly in those tests.

Realizing this is an old quote, but I keep seeing this brought up. I thought all these knives were sharpened at 15 degrees or something. ?

So, do you expect to see differences in the edge holding properties between the front and rear portions of a Mora 2000 blade? Even if they're sharpened at the same angle, you have very different thickness at the top of the edge bevel. Maybe you could give one of these a try & see?

 

[Broos]

I'd like to hear ideas from anyone that can attempt to explain how an edge retention test can show that a softer and less wear resistant steel has better edge retention than a harder more wear resistant steel.

I do not think this is possible in the real world with a proper test and method.

Unless there is zero wedge force (ie. both sides of the material exert zero force on the blade immediately after the material is cut), the thickness of the bevel will absolutely affect the force required to cut - it could be negligible in some cases, but I question whether it is negligible cutting manilla rope - and you can't measure it or determine whether it is neglible without measuring force required to cut the wear inducing media (rope) - which this test does not do.

 

[the possum]

Unless there is zero wedge force (ie. both sides of the material exert zero force on the blade immediately after the material is cut), the thickness of the bevel will absolutely affect the force required to cut - it could be negligible in some cases, but I question whether it is negligible cutting manilla rope - and you can't measure it or determine whether it is neglible without measuring force required to cut the wear inducing media (rope) - which this test does not do.

And that's my point. The edge thickness would be very relevant if he were testing how much force it took to cut through a thick piece of rope (in the middle), as other folks commonly do, such as Phil Wilson mentioned earlier. In that case, you need identical edge thickness/geometry or it will throw off the amount of force required due to wedging.

But, he's not testing that. He is measuring sharpness by using a tiny thread- after a given number of cuts through the thicker rope. So really I don't see how the wedging issue would really come into play, since your testing medium is much thinner than the edge bevel on most knives.

So again I ask, if we're only trying to determine how the sharpness is degrading in that last tiny fraction of a milimeter at the very edge, what does it matter how thick the edge is at the point where it's already cut & passed through the thread? If the Mora 2000 pictured above has its entire edge sharpened uniformly at the same angle & grit, would you expect it to take differing amounts of force to cut through a piece of thread using the forward or rear portions of the blade?

 

[DennisStrickland]

you certainly have worked at it.i use cardboard and find my results have a direct correlation with whitetail deer and feral hogs.sisal & hardwoods may be o.k.but our concern in tx.is edge retention in the field.not to dis. your method but cutting up animals is our main thrust.i did notice something funny with a alloy in 80's.was testing vascowear on cardboard.went from pretty sharp to dead dull in 2 cuts .this unusal tendcendy was confirmed by some other writers.most alloys lose edges gradually.vasco goes from sharp to dull in 2 seconds.at 70 yrs. i'm not as enthustic about testing.i'm really glad to se you youngins carry the flag.

 

[nozh2002]

you certainly have worked at it.i use cardboard and find my results have a direct correlation with whitetail deer and feral hogs.sisal & hardwoods may be o.k.but our concern in tx.is edge retention in the field.not to dis. your method but cutting up animals is our main thrust.i did notice something funny with a alloy in 80's.was testing vascowear on cardboard.went from pretty sharp to dead dull in 2 cuts .this unusal tendcendy was confirmed by some other writers.most alloys lose edges gradually.vasco goes from sharp to dull in 2 seconds.at 70 yrs. i'm not as enthustic about testing.i'm really glad to se you youngins carry the flag.

Thanks a lot. I really appreciate your kind words. It is hard work and I even damage my wrist in result of this exercise and it is important to know that some people find it useful and this was not waste of quite an effort.

Thanks again and I really like to see your testing results if you can share them with us. It is important to me to see and compare my results to other independent results.

Thanks, Vassili.

 

[Broos]

And that's my point. The edge thickness would be very relevant if he were testing how much force it took to cut through a thick piece of rope (in the middle), as other folks commonly do, such as Phil Wilson mentioned earlier. In that case, you need identical edge thickness/geometry or it will throw off the amount of force required due to wedging.

But, he's not testing that. He is measuring sharpness by using a tiny thread- after a given number of cuts through the thicker rope. So really I don't see how the wedging issue would really come into play, since your testing medium is much thinner than the edge bevel on most knives.

With this method, you have a test of two knives, with varying blade shape, varying primary grind angle, and varying bevel widths. Then cutting a thread to test sharpness.

It's unknown how these differences in geometry relate to the force required to cut the rope, or the wear experienced by the edge (how differences in geometry affect the pressure exerted on the very edge during the cut).

For example, the blade with the greatest wedge force will compress and tense the rope more. Can this difference caused by geometry substantially affect the results? Also it is possible that the blade that cuts the thread with the least force may be the blade that requires the greatest force to cut the rope. Does this matter?

The OP and many others thinks the differences in the blades does not affect the results. Given the fact that no one understands how the differences in the blade geometries or profiles actually does affect the test, my opinion is that you should not make this assumption.

If you want to test steel, you need to start with equal geometry or you will be testing knives, not steel. What can be concluded from these tests is "Knife A cut thread at a lower force after XX cuts of X/Y" manilla rope than knife B" or possibly "knife A was sharper after XX cuts of manilla rope than knife B". It does not tell you which knife cuts rope the best for the longest. And it certainly does not tell me which STEEL has the best edge retention!

And I'm still a little taken aback by how little disagreement there is when he boldly states that his test proves that the softer & less wear resistant steel has better edge retention than the harder and more wear resistant steel. Whereas I would start looking for the factors that led to an erroneous conclusion.

So again I ask, if we're only trying to determine how the sharpness is degrading in that last tiny fraction of a milimeter at the very edge, what does it matter how thick the edge is at the point where it's already cut & passed through the thread? If the Mora 2000 pictured above has its entire edge sharpened uniformly at the same angle & grit, would you expect it to take differing amounts of force to cut through a piece of thread using the forward or rear portions of the blade?

No, but I would suspect the two edges may wear differently when cutting, and I would expect the thinner edge to generally cut requiring less force. Isn't how hard it is to cut something the real measurement we want to take when trying to measure edge retention? I would rather know which knife cuts manilla rope using the least amount of force for the longest time, rather than which knife cut thread the best and never knowing for sure which knife cut rope the best.

 

[cotdt]

You need to do pure push-cutting (no slicing) or the steels that develop micro-serrations (like D2) would have an advantage.

 

[nozh2002]

This is no more then theory until it is backed up by testing.

I am not convinced in this microserration theory. Because I can not imagine how natural and random wearing out process will end up in saw like structure with sharp teeth.

Most likely it will be bumpy road then sharp saw.

Thanks, Vassili.

 

[cotdt]

This is no more then theory until it is backed up by testing.

I am not convinced in this microserration theory. Because I can not imagine how natural and random wearing out process will end up in saw like structure with sharp teeth.

Most likely it will be bumpy road then sharp saw.

Thanks, Vassili.

D2 has large carbides so the softer parts of the alloy wear away leaving the carbides behind, leaving "teeth" that can be seen in electron microscopes. It indeed looks like a saw.

 

[cotdt]

Please also test some ceramic knives. I'm curious to see the results. Also, Hitachi Super Blue steel.

I also think there should be separate tests in regardings to slicing versus push-cutting. There is also a lot of variability in this type of testing so there needs to be a lot of repeat trails.

Why is your website in Russian? I would love to read it, in English.

 

[nozh2002]

D2 has large carbides so the softer parts of the alloy wear away leaving the carbides behind, leaving "teeth" that can be seen in electron microscopes. It indeed looks like a saw.

Can you provide pictures. Last what I saw from Sandvic labs look like wide road with little stones bumping out dirt a little, not like saw.

Again knife marketing departments came up with all sort of "ideas" but it was never proven by real tests.

For example best steel ever for edge holding is Dozier D2, but not because of large carbides - only because of Dozier himself, other D2 does not show too much performance.

Now Carbides may help in wear resistance but microsaw is myth so far to me until it is proven, that in did random wearng process somehow form saw-serration tooth.

Thanks, Vassili.

 

[cotdt]

Can you provide pictures. Last what I saw from Sandvic labs look like wide road with little stones bumping out dirt a little, not like saw.

Again knife marketing departments came up with all sort of "ideas" but it was never proven by real tests.

For example best steel ever for edge holding is Dozier D2, but not because of large carbides - only because of Dozier himself, other D2 does not show too much performance.

Now Carbides may help in wear resistance but microsaw is myth so far to me until it is proven, that in did random wearng process somehow form saw-serration tooth.

Thanks, Vassili.

Do microscope images not count as evidence?

http://www.imsteel.com/diesteels_dc53_test_report.htm

http://www3.telus.net/BrentBeach/Sharpen/norton3x.html

Of note, compare the D2 against plain carbon steel (after wear):

D2:

plain carbon steel:

A2:

You can also compare D2 against CPM-D2. CPM-D2 in theory should be a lot finer grained and less toothy after initial wear.

 

[nozh2002]

I can do same pictures, and this one first show coarse edge (at best if not just damaged, which I pretty sure first picture show, and compare scratch from abrasve on different pictures - they are different in size and randomly directed for some reason on second two pictures) and second does not show any tooth or microsaw - I can pick dull knife and make same pictures.

You were refering to electronic microscope pictures with microsaw made of carbide tooth clearly visible:

"..."teeth" that can be seen in electron microscopes. It indeed looks like a saw..."

Do you have any pictures of that?

Thanks, Vassili.

 

[cotdt]

You were refering to electronic microscope pictures with microsaw made of carbide tooth clearly visible:

"..."teeth" that can be seen in electron microscopes. It indeed looks like a saw..."

Do you have any pictures of that?

Thanks, Vassili.

You don't really need the magnification of an electron microscope to see the grains. Here are microscope pictures at 1400x:

The carbide grains in D2 are 50 microns in size. It is 50,000 times larger than its secondary carbides. 440C and ATS-34 have this same issue.

 

[nozh2002]

So as I sad - has nothing to do with saw or serrations - like stones sticking out dirt trail. And if this is 50 microns - it is pritty dull, bumpy, but dull, not saw at all.

Thanks, Vassili.

And this is same pictures from Sandvic I mentioned before - nothing new.

 

[DennisStrickland]

this is off subject but may be interesting to some of you.talonite mostly if not completely is cobalt i believe it's a cast product.some makers have used it in their knives ex. simonich, boye ,mike franklin in 70s & 80s.this stuff rockwelled around 44 but was extremely wear resistance .never rust since it was ferrous free.exspensive but would'nt out perform good steels.until 20 or so yrs. eye surgeons used obsidian flakes which had a sharper edge edge than any steel.lasers replaced obsidians.the sharpest thing i've heard about recentally is a diamond knife.this are used to slice extremely thin tissue samples for micro studies.lasers heat makes them useless in this procedure.maybe one of us in this bunch can expound on this.

 

[the possum]

With this method, you have a test of two knives, with varying blade shape, varying primary grind angle, and varying bevel widths. Then cutting a thread to test sharpness.

It's unknown how these differences in geometry relate to the force required to cut the rope, or the wear experienced by the edge (how differences in geometry affect the pressure exerted on the very edge during the cut).

Right. It's a "given fact" as you said. Nothing can be assumed until it's rigorously and thoroughly tested. Especially now if we think the results will change if we regrind a drop point into a tanto point (blade shape). We'll never know whether a machete really clears brush better than a tactical folder until someone buys 10 examples of every kind made and spends 40 years painstakingly testing them against every kind of brush/vegetation known to man.

Can this difference caused by geometry substantially affect the results? Also it is possible that the blade that cuts the thread with the least force may be the blade that requires the greatest force to cut the rope. Does this matter?

Sounds like an excellent project, Broos. Let us know your results.

If you want to test steel, you need to start with equal geometry or you will be testing knives, not steel. What can be concluded from these tests is "Knife A cut thread at a lower force after XX cuts of X/Y" manilla rope than knife B" or possibly "knife A was sharper after XX cuts of manilla rope than knife B". It does not tell you which knife cuts rope the best for the longest.

I ain't even read this whole thread in ages, but FWIW I always took his results as the knife and material together, even if he only mentions one or the other. Like he just did in post #131. He'll go and make a statement like 'D2 is best steel ever' but then throw in the qualifiers about the maker, knife, etc.

And it certainly does not tell me which STEEL has the best edge retention!

Understand that I'm not diametrically disagreeing with you here, but I would really love to see a test that would meet your standards. I just always come away from here with the impression that nothing can be done to satisfy everyone. And those who try are invariably shot down for even DARING to suggest that they actually learned something from their testing.


Also, since we're on the topic of assumptions, I might point out we all seem to make them.

Isn't how hard it is to cut something the real measurement we want to take when trying to measure edge retention? I would rather know which knife cuts manilla rope using the least amount of force for the longest time, rather than which knife cut thread the best and never knowing for sure which knife cut rope the best.

No, not always. Sometimes I don't care if it takes an extra pound of force, I just need something cut right now. There ain't too many farmers who will stop to touch up their blade halfway through something- it's more a matter of 'get the job done, and then see how bad the edge looks'. So I don't see the OP's approach as any less valid.

Hope I ain't being too gruff here. Ain't been in a good mood... If you're ever up this way maybe we can hash it out over a couple beers, at least until we get the knives out. (then we switch to bourbon. )

 

[Any Cal.]

Wow, you are still testing Nozh? Good job!

I really like the approach you are using, and you have me wanting to put up Doziers D2 against some other manufacturers for fun.

I have actually used a couple of your techniques, like keeping the edge from touching anything after making the cut, for some of my own small bits of testing.

I am also keeping a closer eye on how an edge behaves as it degrades; does it lose sharpness slowly, keep a keen edge for a long time, or keep a dull edge a long time

 

[Broos]

Nice pics and interesting links, cotdt.

Thanks for the invite, Possum - I'll bring some George Dickel, too.
I like all testing, like all results, question some conclusions made, and for some strange reason have had an occasional interest in mechanical testing since studying it in college.

D2 @ HRc61 has lower edge retention than FFD2 @ HRc65. Especially given what we know about the physical properties of them both. And no thermal heat treatment can give D2 @ HRc61 the characteristics it would need to compete with FFD2 and other "super-steels" in edge retention. Yes, the fact that the opposite of this is posted at every opportunity, with no qualifications, and no mention that every other test done (one more scientific and two more experienced) has shown the opposite, occasionally irritates me enough to post to the contrary.

Sorry for quoting you as a springboard for a rant.

 

[DennisStrickland]

reviewed this info again.would like to see you have some fun like cutting up fish or game.your testing is one of the most impressive things i've seen in my 70 yrs.vassili,if i had a lab i would want you to run the operation.your tenacity equals a zen master.ordered a spyderco mule cpm 4 from e-bay today.