As a summary of the above, chopping well seasoned small diameter wood (2-4"), mainly juniper and spruce. The following were used until when shaving arm hair enough draw and force had to be used that the skin was abraded and/or cut:
Fiskars : 764 - 850
Bruks : 852 - 894
VTAC : 415 - 525
Again as noted the Fiskars and VTAC were significantly modified geometry wise, the bit was reduced in angle which will dramatically increase performance. The VTAC is still more obtuse than the Fiskars so the above is not a comparison of steel alone. Interestingly enough, it took longer to sharpen the Bruks after each honing, this only meant like 2 minutes instead of a minute and a half for the Fiskars. The blunting was all deformation based for each axe and thus wear resistance through carbide volume would just lower performance.
I am also not confident that those ranges represent the extremes of performance, especially on the low end. It is simply too difficult to tell when shaving has been lost because the change is just so slow in extended use that there is almost no difference after even 100 more chops. I would strongly recommend to anyone doing that type of comparison to have a reference blade in a very high corrosion resistant stainless (to keep the sharpness constant) at the exact level of blunting that the cutting will be stopped. If you use this as a reference point for the shaving it would make it more consistent.
There is not a clear correlation between hardness and strength as it relates to thin sections.
Hardness is actually a measure of strength on a thin sections of material as it only effects a shallow region. Landes has also directly measured the ability of edges to resist deformation right on the very level of the sharpened edge itself noting the extent of deformation vs chipping. Deformation is highly correlated to hardness and chipping to carbide volume, just as it is for thicker sections. As for knife makers in general, it is not the case that all, or even the clear majority support your assertion that hardness of a knife edge is not the dominant factor when determing if an edge will deform. Case in point :
http://www.thearma.org/essays/impacts.htm
"The ability of any material to penetrate and displace another is heavily dependant on hardness. Harder materials will resist deformation to greater degree than softer more malleable ones. This concept is so elementary that it renders many aspects of the above questions academic. Yet, as with many things regarding swords, common sense is far too easily thrown out the window in order to better suit our preconceived fantasies about historical blades. "
This is in regard to two edges hitting but the exact same arguement he proposes would follow for blades cutting nails. Specifically :
"The two greatest determining factors in the question of a metal edge to penetrate (cut) without itself being deformed in some way would have to be heat treatment and edge geometry. Heat treatment in blades can almost be distilled down to the simple concept of the perfect compromise of softness versus brittleness for the given application. The ability to deform without failure is due to ductility. The ability to withstand deformation is due to hardness."
Truth is I don't know what steel my Henckels is made of but it certainly acts like a fairly soft, low carbide stainless. I straighten the edge with a sharpening steel everytime I use it and I resharpen the edge entirely about once a month. I use it to cut chicken bones and it rolls everytime. If I used it to chop hickory, it would roll everytime. It doesn't hold an edge worth a damn, BUT I guess it has wonderful "edge stability".
No, if the edge deforms easily then it obviously is not stable:
http://www.cutleryscience.com/articles/edge_stability_review.html
Production kitchen blades are cited usually at 52/54 or 54/56 and as with al production knives these are the upper limits so the reality is they will be at a minimum of 1-2 HRC points lower very frequently, Wilson has noted as much as a 5 HRC point difference even in high end production folder steel. Obviously you would not use a random kitchen knife to guage the ability of a class of steels, especially when it isn't even known which steel is used in said kitchen knife. The heat treatment is also not going to be optimal, espect lots of retained austenite, enlarged grain and a higher than optimal carbide volume as they will be undersoaked.
What kind of performance would you expect out of a better blade as compared to what the cheap hatchet in the first post accomplished? What performance areas can be improved upon? Do they even have to be performance related?
For the specific work performed, I would wanted reduced shock in hand, better precision in the cut and more raw cutting ability. Ideally maybe 25%-50% better chopping ability than the Bruks on that size of wood. I would be surprised if better than that could be reached by a 10" blade. The steel should also be significantly harder, maybe 5-10 HRC points, and all of these should combine to greatly increase edge holding. At the same time it should still have the necessary toughness to minimize cracking on a hard contact.
As an example, L6, 66 HRC edge, spring spine, 2" wide, 10" blade, dual 2/3 convex grind, tapered tang, dynamic balance through the tip. Edge for this type of work at 0.025"/8:0.010/12:0.001/14. I do not know if that profile would be stable, but I would be surprised if it could be thinner based on what I have seen. I am hoping the high hardness would allow for the reduced thickness, but you lose rigidity in the power cubic so it is difficult to gain much.
I know that 0.035/8:0.015/14 degrees is actually stable even on 58/60 HRC 52100-mod even when sloppy cuts are made on dead pin woods, so I know it should be possible to reduce this significantly with a stronger steel and if a more restricted cutting technique is used. Here are a couple of shots (before and after in the same picture) of the type of hard wood cutting I mentioned in the above :
and
By the way, I think it would only be fair to point out that several competitors were disqualified at the Blade Show (as I recall) because their edges took too much damage.
Is there an actual specific limit to this or is it just eyeball? The edges get damaged pretty much after every use at some level.
They seem to be pushing the geometry so much, that perhaps steel choice wouldn't have mattered much (within reason).
Note that while properties like toughness and wear resistance will change dramatically from one steel to the next, the actual strengths do not assuming the hardness is the same.
Also, Daniel Winkler has said he makes his comp cutters with an edge far sharper than what he would ever sell to a customer for real world use. This should also tell us something.
The cutting competitions are not well correlated to actual work stress, well yes, but that is obvious for many reasons. I proposed a number of tasks which would be more directly correlated some time ago, but they are obviously not as exciting to watch. To be frank this is a necessary, and likely critical, factor.
One thing which is interestingly lacking in a discussion of such knives is the dynamic balance point. There is a lot of talk about speed, but the only reference I see being made is always just to static weight in hand through the center of mass, even among the guys who win. Ref :
http://www.bladeforums.com/forums/showthread.php?t=353834
This is ironically, yes, a 5160 blade, no great carbides there, but the knife does very well in such cutting competitions :
"For this generation, Dan wanted to ensure that he had a quick blade, and gave much thought to putting weight where it would do the most good - without resulting in a slow, blade-heavy knife. The blade shape - with more width forward – is a result of this design philosophy. As is the most striking design feature of the blade: the nearly full length fuller. This feature reduces mass and allows for a broad, powerful blade that is surprisingly quick in the hand. Dan even went to the extra step of implementing a slightly recessed spine for reduced drag. – it is slightly thinner than the area above the fuller, but still thicker than the area below (edge side) the fuller.
Perhaps the second most striking feature of the blade is the gentle and graceful recurve of the cutting edge. Such a design puts weight a bit more forward for chopping and Dan has found it to be more resistant to twisting – which is a good thing."
Note the focus of weight here strongly speaks of a static measurement (weight forward) to determine a dynamic quantity (speed). Where I wonder is the dynamic balance point on that knife? Where is it located ideally for such knives, to me it would seem to be to be through the tip?
-Cliff
