Another Blackbird down(updated-got replacement)

[Thomas Linton]

Again, my non-expert position is that we don't know why the knife broke.

And meanwhile:

Shouldn't correctly treated steel flex rather than break? (Yes and yes, and if you want to actually know something about axes readhttp://www.orionn49.com/choosing_an_axe.htm)

No. Not all steel flexes under load.

This has nothing to so with axes.

Machetes are quite capable of chopping hard wood and they have thin edges.

If you want to compare this knife to a machete, should they not have similar material, RC, and geometry? If this knife was as soft as the typical machete and made of simple carbon steel it might not have broken this way.

Even axe heads vary more than you think, and when they are solid wedges it isn't for the reason that you imagine.

Yes, axe heads vary a great deal. But none of my axes have heads that are, literally, "wedges." They are all convexed to some extent or another to keep more steel behind the edge to prevent damage. That is how a proper axe came in the first place back when people used axes on a regular basis. Nor are they "knife-hard."

And this has nothing to do with axes.

And the state of the art custom large choppers that makers like Gavkoo and CKC [sic] are making are very fine edged: Gavko Excalibur vs CKC [sic] Forrester XXXL.

The "state of the art" is a matter of opinion, and very successful choppers differ in their opinions. And to make a reasoned comparison to the "bird," the two knives mentioned -- and the F-1 that you mention in a later post -- would need to be steels which, in the actual knives, were at least very similar in terms of toughness. In addition, the blade geometry should be very similar Are they? I think not.

All these of blades work perfectly well. And when good steel is too thin then it will ROLL rather than chip. Your BKRT didn't because one of their notorious sins is blowing the heat treat on the edge by grinding too fast and getting the metal too hot. (In which they are hardly alone, to be fair to them.)

You could be right in your ultimate conclusion, but not all steels roll rather than chip. Some -- properly heat-treated -- just fail by chipping. One would be advised not to select such steels for an impact tool.

 

[meanwhile]

Again, my non-expert position is that we don't know why the knife broke.

In an absolute sense, yes. But I think we can reasonably say that some possibilities are extremely remote - eg aliens, trees that bite knives - and others much more probable - eg bad HT, HT ruined by too fast grind.

And meanwhile:

No. Not all steel flexes under load.

I believe that I wrote GOOD steel.

This has nothing to so with axes.

I wasn't the one who raised them.

If you want to compare this knife to a machete, should they not have similar material, RC, and geometry? If this knife was as soft as the typical machete and made of simple carbon steel it might not have broken this way.

Not if you understand the actual meaning of the word "compare", no - two things do NOT have to be exactly the same for a comparison to be made. But I won't bog down in this silliness because it's not just machetes that can chop without problems.

Yes, axe heads vary a great deal. But none of my axes have heads that are, literally, "wedges." They are all convexed to some extent or another to keep more steel behind the edge to prevent damage. That is how a proper axe came in the first place back when people used axes on a regular basis. Nor are they "knife-hard."

The answer to this is so what? Some axes are actually hollow ground:

..The World Of Axes is not limited by your collection! Although I am sure that it is splendid.

And this has nothing to do with axes.

Again, tell that to the person who thought otherwise - the one who I was debunking.

The "state of the art" is a matter of opinion, and very successful choppers differ in their opinions. And to make a reasoned comparison to the "bird," the two knives mentioned -- and the F-1 that you mention in a later post -- would need to be steels which, in the actual knives, were at least very similar in terms of toughness. In addition, the blade geometry should be very similar Are they? I think not.

The geometry of an F1 does not need to be the same as that of a Blackbird for the F1 to be used to disprove the silly idea that small to medium knives should be expected to self destruct on chopping! If you think that the geometry of the Blackbird is at fault, then you should say why. But this would be a silly thing to say (although it is what you are saying!) because plenty of people have used the thing for light chopping, it is a pretty damn standard FFG, and baton cutting is an essential function for a knife of this kind - and if a knife is tough enough for batoning, it should be tough enough (and more, with a small knife) for chopping.

You could be right in your ultimate conclusion, but not all steels roll rather than chip. Some -- properly heat-treated -- just fail by chipping. One would be advised not to select such steels for an impact tool.

By definition, no good knife steel will fail in this way. Certainly not steel that is good for a knife of this kind.

My conclusion remains that this is a single off-knife from a good design and maker, that HT or overheat in grinding is probably to blame - and that talk by people who think they are Mystic Masters Of Choppery about trees that bite knives as they are being chopped belongs in LOTR.

 

[wouldestous]

im no expert on steel composition, heat treatment, edge geometry, steel flexibility, rockwell hardness, ergonomics or tempering. but i have cut small trees, shrubs and vines for hours on end with a machete. thats what you want for clearing trails. my favorite machete was twenty bucks or so delivered and has worked fine for hundreds of hours. ymmv.

 

[Thomas Linton]

Please, don't rule out aliens. Silliness, aside from attempted insults, has its place.

As for your position that "good" steel is only that which rolls instead of breaks at failure levels, that is one viewpoint. Usually, experts ask, "Good for what?" By your proposed standard, 154 CM is not "good." Compared to 3V, the material of one of your comparison knives, and compared to other "carbon" and stainless steels, 154-CM's elastic range is much narrower. 3v is "good" by your proposed standard because it is far more likely to bend, having a far wider elastic range than the relatively brittle 154 CM. Yet experts may be very willing to trade some brittleness for increased corrosion resistance or greater resistance to abrasion ("edge holding"). l suspect the experts would not agree with your definition of "good."

I suppose you are right about comparisons. One can compare pudding (Chocolate, please.) with a knife - but not usefully for present purposes.

So how about seriously comparing the knives you brought into the thread for the express purpose of proving something about why this Blackbird failed? These other knives are dramatically different in length, geometry, weight, and material. And what is the relative hardness of the three knives? The Blackbird is designed to run 58-60 RC according to the designer.

I mentioned the F-1, with its very different geometry and materials, solely because you compared it to the Blackbird for purposes of evidence that if the F-1 did not break, the Blackbird (regardless of how used on what material) must have had poor HT. I did not make your "straw-man" argument that someone is claiming "all small or medium knives should be expected to self-destruct on chopping." (Not to be catty, it seems important to this discussion that knives do not "self-destruct." It takes a user and a use -- all variables - to bring damage, and you have not controlled for those variables in any useful sense.)

As to whether "small to medium knives" should chop without being damaged, that would depend on the knife, the user, and the use - not the size. A puukko is a perfectly respectable smallish knife and favored by many for "survival" (if not a "survival knife" to all). I suspect you could easily destroy it chopping wood as it is not made to chop wood. I am holding a 5" Breeden "survival kit" knife made only of a piece of 3/32" O-1. I cannot imagine what you would have to do to break it attempting to chop wood - not that you would accomplish much chopping. The subject is a particular knife with particular geometry made from a steel not optimal for impact.

In terms of stresses produced, there is, of course, considerable difference between chopping and batoning. I can baton/have batoned with a MORA. I have batoned with an cheap Imperial Scout pattern slip-joint - carefully - with no damage. Chopping would destroy the MORA or slip-joint knife for little or no return.

13.5mm thick 154-CM in a FFG at RC 60 is arguably, and aside from length and weight, a lesser choice for a chopping tool. But the designer speaks only of "heavy use" and batoning ("static shock"). He does not mention chopping directly or by necessary implication, whatever one thinks of the role of a "survival knife." Nor does he picture chopping. http://www.hedgehogleatherworks.com/Blackbird-SK-5-Survival-Knife-p/bbsk-5.htm (The designer, by the way, does not seem to have put the "ultimate" tag on his knife. Ontario did that. It's one of their favorite adjectives.)

As for the "good" design, the designer makes knife sheaths and this is his first knife design - a Kephart with a RAT handle (that I like). There are only so many ways to build a knife, and this design is nothing new. Mr. Kephart, if alive, would appreciate your support for the spear-point knife, as would all the others who have made then over the centuries.

Respectfully, I seems like your reasoning comes down to this:
> other very different knives and other examples of this very knife didn't break when "chopping," knowing nothing about what or how the others chopped and without regard to the different geometry, length, hardness, or materials of the comparator knives;
> knives of this size, without specifying anything else about them should not break when "chopping";
> this is a "good design" and "good maker";
Therefore, this knife must have a poor HT because it broke.

Again, perhaps so. Alleged inconsistency in HT is ofter cited for why Ontario is a lesser-quality maker. (None of my Ontario knives have sustained any damage, but I have only broken one knife -- totally my fault - chopping with a thin ATS-34 model).

(And yes, axes do come concave. My first was a Bridgeport that was well and truly concave. It didn't work well. Not "good." Among other deficiencies, it is not concave like the lovely Plumb that came next.)

 

[me2]

All steel does flex under load. The question is what happens when the limits of its flexibility are reached. Does it bend or break? And no, all good steel does not roll instead of chip. I have a Carbon V Cold Steel blade that did both, doing similar tasks, light limbing and such. Ffg,1/8" spine, , 1 3/8" wide, 12°/side bevel, 0.017" behind the edge, HRC 60, tested on another bought at the same time. The damage was limited to the edge bevel and should come out in the next 2-3 sharpenigs. Right task or not, this blade shouldn't loose pieces like this from what was described.

 

[meanwhile]

Please, don't rule out aliens. Silliness, aside from attempted insults, has its place.

As for your position that "good" steel is only that which rolls instead of breaks at failure levels, that is one viewpoint. Usually, experts ask, "Good for what?" By your proposed standard, 154 CM is not "good."

I can't be bothered to find and check info on 154CM. But if it chips rather than rolls when overstressed in reasonable use ranges, then it is certainly not good for the purposes that the Blackbird is sold for.

However, that's a big "if" - because I have no confidence in your ability or knowledge.

Compared to 3V, the material of one of your comparison knives, and compared to other "carbon" and stainless steels, 154-CM's elastic range is much narrower. 3v is "good" by your proposed standard because it is far more likely to bend, having a far wider elastic range than the relatively brittle 154 CM.

Yep: I was right. Your logic is silly. It doesn't matter a whit that one steel has a wider elastic range than another, ONLY WHAT THE BEHAVIOUR INSIDE THE RELEVANT RANGE IS.

Yet experts may be very willing to trade some brittleness for increased corrosion resistance or greater resistance to abrasion ("edge holding"). l suspect the experts would not agree with your definition of "good."

Your fantasy experts wouldn't. But why should you expect me to be impressed by what are effectively voices inside your head???

(Also: you almost certainly know nothing about edge retention - like most people here...

I suppose you are right about comparisons. One can compare pudding (Chocolate, please.) with a knife - but not usefully for present purposes.

You can certainly compare an F1 with a knife of the same size designed for the same purpose.

So how about seriously comparing the knives you brought into the thread for the express purpose of proving something about why this Blackbird failed? These other knives are dramatically different in length, geometry, weight, and material.

No. An F1 is not dramatically different in most of those things; you are being silly. Regarding those other implements, again I have to dumb down because you weren't smart enough to understand plain English, it seems: someone said that axes show that only heavy wedge blades are safe in chopping, and part of my answer was that many thin long blades - eg billhooks - have been used to chop wood for centuries. I am sorry that this confused you, but if you still don't understand then it is not my problem.

I mentioned the F-1, with its very different geometry and materials, solely because you compared it to the Blackbird for purposes of evidence that if the F-1 did not break, the Blackbird (regardless of how used on what material) must have had poor HT.

I am puzzled because I can't believe anyone has reading comprehension as poor as you are pretending to. To quote me, myself, and I:

In an absolute sense, yes. But I think we can reasonably say that some possibilities are extremely remote - eg aliens, trees that bite knives - and others much more probable - eg bad HT, HT ruined by too fast grind.. The geometry of an F1 does not need to be the same as that of a Blackbird for the F1 to be used to disprove the silly idea that small to medium knives should be expected to self destruct on chopping!

..So again, my contention was that the F1 proves that small knives can chop without being eaten by trees, NOT that it proves that the failure of this knife was poor HT. (Although it is the most likely possibility.)

I did not make your "straw-man" argument that someone is claiming "all small or medium knives should be expected to self-destruct on chopping." (Not to be catty, it seems important to this discussion that knives do not "self-destruct." It takes a user and a use -- all variables - to bring damage, and you have not controlled for those variables in any useful sense.)

If you didn't mean to endorse that view, then you write *very* badly.

As to whether "small to medium knives" should chop without being damaged, that would depend on the knife, the user, and the use - not the size. A puukko is a perfectly respectable smallish knife and favored by many for "survival" (if not a "survival knife" to all). I suspect you could easily destroy it chopping wood as it is not made to chop wood.

What you suspect doesn't doesn't matter. (A Mora Clipper is quite typical of Puuko's bladewise and I can tell you empirically that the results of chopping with it are boredom and a new appreciation for the meaning of the word "futility": I know this because I just tried a Clipper on a hand piece of wood, rather than making stuff up and claiming it is evidence. Oh - and my Clipper is zero edged.)

In terms of stresses produced, there is, of course, considerable difference between chopping and batoning. I can baton/have batoned with a MORA. I have batoned with an cheap Imperial Scout pattern slip-joint - carefully - with no damage. Chopping would destroy the MORA or slip-joint knife for little or no return.

The Mora 2000 is Cliff Stamp's standard benchmark knife in its size; go to his review and you'll find chopping test data - the knife was entirely undamaged. It's very hard to damage a small knife in chopping because it is too short and light to store much energy - the amount of energy that a Mora 2000 can reasonably deploy in a chop is a tiny fraction of the energy that batoning it with a decent piece of wood will provide. This shouldn't be hard to realize ("Ugh! Branch heavy, Mora light - branch long, Mora short!") so I'm rather lost as to why even you don't get this.

And the ONLY "considerable" difference between chopping and batoning as far as the edge of a small knife is concerned is that batoning will involve much greater forces! Really: stop trying to hide behind vague bs. If you think there is another difference, then say what is.

But the designer speaks only of "heavy use" and batoning ("static shock"). He does not mention chopping directly or by necessary implication, whatever one thinks of the role of a "survival knife." Nor does he picture chopping.

http://www.hedgehogleatherworks.com/Blackbird-SK-5-Survival-Knife-p/bbsk-5.htm

Again, you have by-passed common sense: the SK5 is (like the Mora 2000 or Clipper) too short and light to be a useful chopper. That does not mean that it should be expected to explode when used to chop! A spade makes a lousy butter knife; that doesn't mean that you expect it to break when it touches a loaf of bread...

 

[knifehunt]

Don't worry, they will replace the knife.... I don't care what anyone says, but if you can't hack off a few branches with a knife it ain't worth a a nickle.

 

[Tbaggin]

Don't worry, they will replace the knife.... I don't care what anyone says, but if you can't hack off a few branches with a knife it ain't worth a a nickle.

Agreed

 

[Tbaggin]

Updated