How brittle is D2?

[Broos]

Right on, Tom. It doesn't take a genius to figure out that D2 is some dang good knife steel.

Cliff, you can go on all you want about razor thin edges and how great they are, but in reality we know that most people want the durability and higher safety factor of a thicker edge, especially when they are taking one knife out to the woods (and may be cutting through some bone). And you continue to use your claimed "material property" of edge stability or now "edge strength" as a basis in fact, yet cannot even answer simple questions about the test baseline conditions, how the test for it is done, or how the test results for it have been correlated to knife use with thicker edges, slicing, or chopping.

And you are trying to compare your D2 blade test and the FFD2 test knowing full well that the tests are not comparable. It is not earth shattering news to anybody that a microscopically thin razor blade type knife is a good cutter. Now when you start chopping these edges into your concrete blocks please do check back in with pictures.

 

[JD Mandrell]

If you can't get a good edge on D-2 maybe it is your sharpening style

I think there is a lot more truth to that than some folks want to admit, With so many "quick and easy" sharpeners out today.

Tom, a staunch D-2 supporter!

+1 :thumbup:

 

[Cliff Stamp]

Cliff I think this is more related to Geometry of the blade than the actual sharpness of the edge.

Any test of sharpness which involves cutting material will be sensitive to geometry because you are either going to apply a specific force and see how much material is cut, or cut a certain amount of material and see how much force it took. The problem is the force which is used is the total force, the force on the edge and all the other forces on any part of the blade which contact the material. But really for measurement of sharpness, only the force on the edge should be considered. No one would say you are "sharpening" a blade when you do the primary regrinds that most have raved about with various folders. But this will lower the force required to cut most materials significantly.

Now when you are doing a cutting test how much of the force is actually related to sharpness? This can actually be calculated with difference methods, but they are prone to extreme error magnification. A more optimal way is to simply reduce all other forces to as close to zero as possible by making sure that very little of the blade actually contacts the material aside from the edge and that the material is not very binding. In the above examples I noted, both of these are true and thus they require a very sharp edge to perform, much more so than an acute edge.

Consider, if you take even the most acute ground edge, a full grind so the edge is 3-4 degrees and blunt it with just one pass right into a UF Spyderco ceramic or slicing one sheet of fine sandpaper, you will flatten the edge just enough so that it will fail any of the above tests of sharpness. The edge is still extremely acute, but the intersect thickness is likely 10+ microns and thus the blade is dull. Even though the edge is still ground extremely acute, it is basically zero sharpness.

To be really specific to your question, the sharpness will be a function of very edge thickness (not the bevel shoulder but the actual intersect thickness which is about a micron or so), and its nature (rounded or sharply cut), and then the edge angle. Tests such as the above are far more sensitive to the first two than the last one. Small changes in the first two will require very large changes in the last one in order to compensate. As an example, awhile back I starting press cutting newsprint to measure sharpness by noting the distance from the point of hold. At the time I thought a one inch distance was impressive, a number of other guys have starting doing it and they achieve 3-5" distances though their edges angles are often double what I was using. They do much better because the blades are just sharper even though they are much more obtuse.

It would be best if the edges were just measured for sharpness by macroscopic shots of the intersect as this removes the force, however there is a problem there in correlating the nature of the very edge, the roughness which would be difficult simply from a picture. This aspect of performance is why some people can make a blade shave easily on a buffer but it has no slicing ability. They have created a very tiny intersect on the edge, < a micron in thickness, but it is fully rounded smooth. Ben Dale and Bob Dozier are two guys who are very good at obtaining edges which combine very high sharpness in both push cutting and slicing, Dale favors high polishes and Dozier coarse edges. Both of them will produce minimal intersect thicknesses and little smoothing.

-Cliff

 

[ADD]

I am paraphrasing but will put into quotes something I read somewhere and will attribute to Bob D. (how is that for being confident in your memory and sources?)

"Cliff Stamp would argue with Einstein about the theory of relativity"



Well, argument spurs discussion...

This thread makes for a great learning experience for us novices when some very good makers post. Thanks

 

[JD Mandrell]

This thread makes for a great learning experience for us novices when some very good makers post. Thanks

Well said, imagine how much better it could have been, or blade forums in general could be, if more true masters of the art could come here and teach us without being harassed by those who cannot achieve what they have.

 

[OilMan]

Well said, imagine how much better it could have been, or blade forums in general could be, if more true masters of the art could come here and teach us without being harassed by those who cannot achieve what they have.

Or imagine how nice it would be if the general population of the forum knew how far some of you would go to out someone who doesn't agree with your own opinions and try to get them kicked off the forums. Most often by putting words in his mouth and then trying to take him to task for them. Even though he helps more people than he supposedly hurts.

 

[Guyon]

Well said, imagine how much better it could have been, or blade forums in general could be, if more true masters of the art could come here and teach us without being harassed by those who cannot achieve what they have.

Nicely put.

 

[db]

This thread makes for a great learning experience for us novices

I'm just wondering, what can we learn from this thread?

 

[Bastid]

Well said, imagine how much better it could have been, or blade forums in general could be, if more true masters of the art could come here and teach us without being harassed by those who cannot achieve what they have.

I have nothing more to add to that since it is an accurate statement.

 

[noss4]

If D2 was not brittle in most cases. Then why don't more makers make large blades out of it ? Some of the D2 defenders here stated they would not be subjecting the D2 to hard shock or impacts or would not want a knife over want a knife made of D2 over 4 or five inches why is this if you don't feel it is brittle ?

I have never used or tested a D2 blade so I'm not judging the steel just asking a question ?

 

[Jeff Clark]

Re: "Cliff Stamp would argue with Einstein about the theory of relativity"

If Cliff had a relevant insight I am sure that he would be happy to discuss it with Einstein or Hawking. That is the open nature of the physical sciences. Scientists expect to be challenged, it is the core of what makes science work. They also tend to be rather direct (aka blunt) when you get into one of these discussions. I have never had my statements challenged more than when I worked for Bob Leighton, at the time the chairman of the Caltech physics department. I could be in the machine shop measuring how much heat is released when sanding aluminum and tell Leighton my numbers and he would question my methods (he was primarily interested in astrophysics, but knew more about material science than I will ever dream about). This was not fun, but he often caught minor errors and clarified the underlying physics.

When you deal with a good scientist they will tend to split hairs about what you represent as general fact. Cliff often qualifies things that I say on the forums. He is generally right. I am often not precise in my statements as a matter of style. I don't take it personal when he "improves" my comments.

 

[Broos]

Just because a knifemaker is more comfortable in making a large knife out of A2 versus D2 doesn not mean that D2 is brittle. It means the knifemaker would rather make a knife that has a 0.01% possibility of failure versus a knife with a 0.02% possibility of failure. There are a lot of large D2 blades out there that have given their owners very good service. And I wonder how many people would take an extremely thin bladed 4.5 degree zero edge knife as their only knife out to the woods knowing they will have to gut and quarter multiple large game animals.

 

[Kohai999]

I'm just wondering, what can we learn from this thread?

1. D-2 is much tougher than the premium stainless steels like ATS-34, but not as tough as many of the other non-stainless steels

2. Doziers are excellent cutters.

3. Swamp Rat had some photos on their forum of one of their D2 knives after being beaten with a hammer. Swamp Rat would cover breakage in that manner. But then, they covered a guy who beat on a knife with a pipe wrench for several hours. Bob Dozier would likely consider hammering on a blade to be abuse, outside normal hard use, and would not cover it. (This does constitute abuse, as defined by Dozier, and I agree. SG)

4. Cliff says…"Johnston has compared ATS34 (a similar high carbide steel) to 1095 and M2, used in a variety of trades, carpet cutting, meat workers, utility (cowboys) and yes, even hunters. He found that 1095 was vastly superior to ATS34 (Bos heat treated) at low angles, the extra wear resistance of the large carbides in ATS34 was not functional as they just tore out of the very thin/acute edges. D2 would have the same performance comparison as ATS34 as it is in the same class of steels."

D2 and ATS34 are now in the same class, according to Cliff. By that, I think he means high carbide alloys….not sure, though.

5. Many hunters in this thread say something like…."All I need to field dress and quarter a S.E. U.S. buck is a Dozier in D2 designed for game."

6. Cliff is advocating razor blade like blades for daily use….."Now if you want to see what high cutting ability actually means, then get a knife made from M2, 66 HRC, with the edge at 0.005"/10 degrees and compare that to a 60/61 Dozier D2 at 0.015"/18 degrees and see which one cuts better, needs to be sharpened more frequently and is easier to sharpen."

7. Tom Krein says this, which I believe is very, very accurate…."…..a thin edge like that is not something I want to put on every knife I make. I can grind them super thin on request, but don't regularly because I don't want the head aches that would come with people chipping them out and breaking the tips off(it WOULD happen). I feel an edge in the .015-.020 range is nice and thin and easily sharpened and much stronger. It is also a big performance jump in geometry than most production knives out there.

No reason to thank me, I just thought that some of you might like the Reader's Digest version, for your wallet.

 

[on_the_edge]

If D2 was not brittle in most cases. Then why don't more makers make large blades out of it ? Some of the D2 defenders here stated they would not be subjecting the D2 to hard shock or impacts or would not want a knife over want a knife made of D2 over 4 or five inches why is this if you don't feel it is brittle ?

I have never used or tested a D2 blade so I'm not judging the steel just asking a question ?

There are countless potential reasons why more makers don't use D2 in large blades. Availability, cost, practical workability in creating the knife, objectives of the maker's themselves, a huge number of alternative steels, etc. To take the fact that there aren't more large-blade D2 knives out there as being indicative that D2 might actually be brittle is baloney and short-sighted. I'm not flaming you, but simply saying there are LOTS of reasons why there aren't more large D2 blades. Whay don't you ask the makers themselves? I am sure they can all provide adequate answers.

 

[Tom Krein]

If D2 was not brittle in most cases. Then why don't more makers make large blades out of it ? Some of the D2 defenders here stated they would not be subjecting the D2 to hard shock or impacts or would not want a knife over want a knife made of D2 over 4 or five inches why is this if you don't feel it is brittle ?

I have never used or tested a D2 blade so I'm not judging the steel just asking a question ?

I make my Ultimate Boar Knives out of D-2. They have a 9" hollow ground blade with a 7" hollow ground top edge. They work very well on Hogs.

If you drop the RC hardness, make them with thicker edge geometry you can easily make a D-2 knife that will work well as a big chopper. Are there better steels for this... I think so. You can do it, but I prefer A-2, CPM 3V or simple 1095 for the extra measure of toughness they supply.

I personally think D-2 is not optimal for choppers, thats why I use A-2, or CPM 3V for my big choppers/camp type knives.

I think D-2 is BEST at a Rockwell hardness of 61 and ground nice and thin (relatively, Cliff ).

No single steel is Optimal for every use, if there was such a steel we wouldn't have the fun of discussions like this.:foot:

Tom

 

[Cliff Stamp]

If D2 was not brittle in most cases. Then why don't more makers make large blades out of it ?

It is just not the current fad steel, 154CM/S30V is common in large blades and they are high carbide brittle steels like D2.

If Cliff had a relevant insight I am sure that he would be happy to discuss it with Einstein or Hawking.

One would hope that would be the case and that it would be openly encouraged. Generally you wish for critical thinking on the part of the questioner, but even without it, it is just foolish to desire a forum where views can not be questioned.

Scientists expect to be challenged, it is the core of what makes science work.

Yes, expect to be and expect it done, you also have to be transparent about all claims, be willing to provide raw data, access even to equipment if someone desires. More than once I showed people around my lab directly and showed them in detail all the work done including the test runs, raw calibration data, and the runs I junked and why I junked them.

Cliff often qualifies things that I say on the forums. He is generally right. I am often not precise in my statements as a matter of style. I don't take it personal when he "improves" my comments.

I think you are being overly generous there, my entire study of edge stability was prompted by an arguement we had right at the start of Bladeforums when you noted that some steels could get sharper than other ones and I said they could not. We discussed this in detail and I realized that what I thought was sharp was no where near close to what you meant by sharp and that was the reason we were reaching a different conclusion.

I discovered that you were using edges at about half the angle I was and that in order for an edge to be sharp from your perspective it had to be significantly sharper than just being able to scrape a few coarse hairs. With this in mind I did some retesting, lowered angles, really focused on maximal sharpness and exactly as you said, some steels do get sharper.

This is the part that never happens in threads like this, all that happens is nonsense like "Wow, Cliff said Doziers edges are thick and obtuse." followed by the Monty Python duck/witch logic. Note I clearly asked for the exact points I made about D2 which were being contended and that was ignored, instead more vague generalities and paraphrases, the exact opposite of how you hold a meaningful debate. Are the facts actually ever considered, that there are knives at a fraction of the thickness/angle Dozier uses, that there are steels which offer much higher performance, that this has all been measured and published, nope.

The part that I find really amusing is in the FFD2 papers they take the P/M process to task for producing brittle steels. When I mention the problems S30V has threads blow up into dozen page affairs, but yet the FFD2 guys have no problems with saying that S30V "... has very poor fracture toughness." direct quote from promotional material on FFD2. Now imagine if I responded in a S30V thread saying that exact same thing and even citing the exact same materials reasons. How would Bastid and company react, but will they take the FFD2 guys to task for "endangering the business of all those who use S30V". Of course not but then you have two makers in contradiction so when your perspective is based on faith what do you do in a contradiction - pretend it never happened.

-Cliff

 

[Broos]

Scientists expect to be challenged, it is the core of what makes science work. They also tend to be rather direct (aka blunt) when you get into one of these discussions.

I heartily agree with this. Science should not be taken as fact if it cannot stand up on its own feet and be explained or defended. I agree that Cliff has a right to challenge, and he does very frequently - but it should be a two-way street. He argues from a stance that he is in posession of the absolute mathematical scientific truth, yet is unable or unwilling to answer questions. And it's not just me.

Many of us do not have a problem if someone can show us where our understanding may be off, and would enjoy the educational opportunity to be corrected by either someone capable of clearly and concisely answering technical questions, or a knifemaker answering from a wealth of experience in the field of knifemaking. Thanks again, Tom.

 

[Kohai999]

He argues from a stance that he is in posession of the absolute mathematical scientific truth, yet is unable or unwilling to answer questions. And it's not just me.

....... to be corrected by either someone capable of clearly and concisely answering technical questions, or a knifemaker answering from a wealth of experience in the field of knifemaking. Thanks again, Tom.

1. To clarify the statement, Broos is not the only one who has issues with the FACT that Cliff "argues from a stance that he is in posession of the absolute mathematical scientific truth, yet is unable or unwilling to answer questions."

2. As far as Cliff dominated threads go, this was a pretty good one, as real information was exchanged, and that IS appreciated. Thanks Tom, and Cliff, sorta.

Best Regards,

STeven Garsson

 

[Tom Krein]

Here are my points/arguments for this thread...

D2- is not brittle.

D-2 takes a fine micro serrated edge and with maintenance (all blades need sharpening sooner or later) and holds a fine micro serrated edge. Enough of the old wives tale about it taking a crappy edge and holding it forever...

If you think D-2 takes a crappy edge you probably need to work on your sharpening technique or tools.

Does D-2 take the finest edge... NO! I have never argued that.

Am I a Cliff Stamp hater or supporter... neither, BUT I think he does make some good points at times.

Do I think super thinly ground blades cut like lasers..... YES!

Do I think super thinly ground blades are for everyone and every task.... NO They are very nice for precision cutting! I carry a thinly ground Spyderco daily.

Am I a D-2 fanatic.... YES! Do I only use D-2?? NO! I also use CPM 3V, CPM M4, CPM S30V, A-2, O-1, 1095, W2, Talonite, and Damscus.

I have said it once and will say it again. There is no single steel that is perfect for every need!

D-2 makes a very nice smaller edc knife and makes a fantastic hunter. The micro serrated edge is VERY aggressive for fleshy type mediums!

Tom

 

[tarmix101]

Well said, imagine how much better it could have been, or blade forums in general could be, if more true masters of the art could come here and teach us without being harassed by those who cannot achieve what they have.

Very well said TLC. Whole heartedly agree with that statement:thumbup::thumbup::thumbup:

Imaginary green chicklets coming your way.