Jerry Hossom :
... if it slows down substantially before it even gets to the bone it will not experience substantial stress on impact. Conversely, if a blade impacts the bone with sufficient force to cut through the bone, it has endured much greater stress.
You are glossing over factors and attributing forces to where they don't contribute, the edge doesn't take the full force of the impact. If I take a knife that cuts through a piece of rope with say 50 lbs of force, then reprofile the the edge so that it only takes 25 lbs, this doesn't change at all the amount of force the very edge sees. All I removed was the force on the sides of the blade that come from wedging the material apart. The stress on the edge comes from the amount of pressure needed to overcome the rupture pressure of the rope and that is the same in each case (with minor complications).
There is no way you can conclude with certaintly that a blade that doesn't make a compete cut and doesn't get damaged would have damage induced if the geometry was altered to allow a complete cut. In fact you can't even elmiminate the possibility that that it might show greater durability than the other blade once the geometry was altered. Take an CPM-3V blade with very obtuse grinds which cannot make the cut, but is not damaged, and compare it to an ATS-34 blade that can do the complete cut without damage. By your logic you can now conclude that the CPM-3V is not as tough. In reality all you can conclude is that one knife cut better and make no statement on toughness.
I do not give up penetration to get strength. They are not mutually exclusive attributes in a blade edge.
Strength is directly correlated to cross section, penetration is negatively correlated. If this correlation didn't exist, there is nothing preventing you from grinding a tip of infinite strength and penetration ability (except for mass, but that tends to increase penetration ability for a lot of stabs). Now there are a few complications, but they are small effects. For example a convex ground tip will be more durable in prying wood than a flat ground tip of similar amounts of metal, because the convex ground tip will take the stress along the upper parts of its bevel, whereas the flat ground tip will allow a lot of force to be concentrated on the very tip. Convex ones tend to break further up from the tip when prying in wood, which obviously takes more force. However, there are other types of prying which would favor the flat ground edge. And if you stick with either geometry, the basic rule holds. Or, for example, you could sharpen the upper part of a knife bevel (false edge), and increase the penetration without lowering the strength significantly (of course you lower the durability of the false edge tremendously), however once this is done, if you want to go further you have to increase the cross section and thus decrease the penetration.
I am just stunned that you can evaluate the results of my reshaping the edge on a machete without having a clue as to what I did.
It is hardly a complicated relationship as it depends on very simple physical laws. If you take for example a 20 degree bevel and apply a convex grind which is in all respects lower, the cutting ability will directly go up and the durability directly down. If your convex bevel is the opposite, then similarly effected in the opposite way are cutting ability and durability. Now you could use a convex bevel which is a lot lower than 20 degrees near the shoulder and over 20 degrees right next to the edge. This would leave the very edge a little more durable, and overall raise the cutting ability. But the edge as a whole is now much more prone to rippling. This is in fact how most machetes get damaged, usually when you hit a knot, or a branch breaks and you hit another laterally, which is really, really bad. And again, similar to the argument for the tips, if this relationship didn't exsit you could make edges of infinite durability and cutting ability.
There is however a further complication which is that drag forces can depend on a complicated manner on cross section, and it is possible to have a blade that cuts better than another, even with a greater cross section and thus strength, if the drag profile is better. I have discussed this with a knife maker who claimed to have shown this comparing flat, hollow and convex optomized blades (oblate curves). His testing confirmed that the convex+ blades were optimal, which from basic principles is sensible. However, this cutting ability ratio won't hold across all materials in a uniform matter. And for every geometry the basic relation between durability and cutting ability will hold. I am getting a few blades to look at this matter myself as it is rather interesting.
Jon Lumpkin :
... C-notch and the V-notch
The C-notch test uses a circular notch in the block, and the v-notch one an angluar cut. V-notch tests give lower failure points as they focus the stress more. Impact toughness tests can be done in two ways, the Charpy and Izod. the difference between them is that with the Charpy values the steel is hit on back of the notch, for Izod testing the notch is facing the hammer.
[blades of the the same size,grind,and edge thickness.]
... which steels would chip and/or bend easiest at the edge when hardened at their proper individual hardness levels.
In regards to strength, and therefore resistance to rolling :
M2 (64-66 RC), D2 (62 RC), ATS-34 (62 RC), O1 (62 RC), A2 (60 RC) , CPM-3V (58 RC)
The difference between the M2 and D2 would be large, for the D2, ATS-34, O1, the change would be difficult to notice unless looked at carefully. You should be able to notice the 2 RC fall off on A2 and CPM-3V. The complication is of course the hardness. CPM-3V can be raised to 62 RC for example, and thus would be right behind D2, however it would lose a *lot* of toughness for a small increase in strength. In general, in the cutlery industry, most of the above would be at the same RC ~59. If this was the case you would see little difference in resistance to rolling. For chipping the list would run pretty much the opposite :
CPM-3V (58 RC), A2 (60 RC) , O1 (62 RC), ATS-34 (62 RC), D2 (62 RC), M2 (64-66 RC)
Of course you could for example, drop the hardness down on M2 to ~58 and its toughness would put it around A2, but again this doesn't make any sense considering the makeup of M2, as you are wasting its potential.
Also,which steel would hold an edge longest in chopping wood or bone
If all the edges are ground at an indentical angle, which is enough so that none of the steels will fracture then the edge holding on wood would be mainly due to strength and thus you would have :
M2 (64-66 RC), D2 (62 RC), ATS-34 (62 RC), O1 (62 RC), A2 (60 RC) , CPM-3V (58 RC)
Bone would be similar as wear resistance tends to run the same way. However you would need a really thick edge on the M2 blade to prevent fracture, and thus the other steels would have vastly thicker edges than needed. If you ground all edges at the level necessary to prevent fracture, the list would pretty much reverse. The cutting ability would obviously be changed as well which would in fact act to enhance the difference in edge retention.
... which would hold the best edge in rope or meat cutting?
This is just strength with just a hint of abrasion resistance :
M2 (64-66 RC), D2 (62 RC), ATS-34 (62 RC), O1 (62 RC), A2 (60 RC) , CPM-3V (58 RC)
With similar levels of differences seen as noted in the above. However there are materials are very abrasive to cut and thus hardness will not always be the primary factor in edge holding. It is possible for example that the higher wear resistance of CPM-3V would over come the hardness disadvantage as compared to A2 and thus it would have a longer edge life on some materials.
Taz :
... HT books are for generic pieces of steel, NOT knife blades.
Knives are used in industry as well. Heat treating is optomized for various shapes, and in fact this is always suggested, as some complicated shapes require careful consideration, but this doesn't break the basic laws which hold for steel in general, regardless of the shape. Again there is a lot of hype in the cutlery industry concerning heat treating, especially about "secret" methods.
A2 is a very tough steel. Very durable, very fine edge, and can take some punishment. That means it is tough.
You can't use a relative term as an absolute it is undefined. I could just as easily say A2 is very brittle, and it would be true if I used S7 as a benchmark for toughness.
All the charpy and v notch tests are all well and good
To be frank, the reason that materials properties are so put down by some makers is that it prevents hype. They are real physical properties. If you take two steels and bend them in a vice, you will notice a much greater resistance from the one with the greater tensile strength, you will notice that one snaps much easier if it has a much lower ductility, and so on. If you are grinding blades then you will notice that the one with a much lower machinability takes much longer to work. That is what these properties measure.
With the 2 knives. if one is damaged, and 1 cuts thru, it would mean that the one that cut thru was obviously tougher
Obviously, however the argument was when both blades were undamaged, yet one cut better, can you claim it is tougher - no, of course not. This logic, as noted in the above leads to insensible conclusions.
-Cliff
Are you sure you axis was A2 and not M2 or D2??? I am not a BM guru, but I haven't heard of any in A2...
Field testing you know! 
