Here are the edge specifics for the Kirk blades, NIB :
A : 0.020 x 0.038" -> 14.7 degrees
B : 0.015 x 0.036" -> 11.8
C : 0.025 x 0.070" -> 10.1
D : 0.017 x 0.034" -> 14.0
Looking at the numbers in a straightforward manner, there is a 20 - 30 degree included spread. It gets even worse if you do a bit of statistics. Due to the small sample, the t-factor is quite large (3.2) and a 95% CI is 17 - 33 degrees. Now his blade angles go almost double each other.
However, as noted in the above, this isn't 100% due to Ray. A part (maybe even the majority) will be due to the measurement. Most people calculate edge angles from measurements of edge thickness and width which have fair size uncertainties in them. Now further consider elements like edge blurring at the shoulder from buffing, curvature due to slack belts, or variation along the edge.
To see just how sensitive the angle is towards light deviations, consider what would result if I was off by just 0.002", just two thousands of an inch. In the worse case scenario, the first line then becomes :
A : 0.022 x 0.036" -> 17.0 degrees
and now it looks much worse. However, before anyone gets worked up about Ray's QC, after I did the above measurements I did some cutting on wood and rope (whittling and push cutting). The performance on all blades was within a few percent so I knew the angle measurements were a little off. Taking them again in a different place along the blades edges resulted in :
A : 0.024 x 0.050" -> 13.5 degrees
B : 0.021 x 0.044" -> 13.4
C : 0.025 x 0.061" -> 11.6
D : 0.021 x 0.044" -> 13.4
Just a change of a degree here and there and you have a totally different perspective. The CI now is 23 - 29 for the included angle, a much tighter tolerance. This is why I generally measure edge angles at 3-5 places along the blade now. It should also be noted these are not CNC blades, and they were test blades.
Eric :
Fatiuge is exactly what I am talking about.
Yes, if you raise your effort the total productivity drops, its why you pace yourself and why I commented on fatigue and why it always has to be kept in check. If you take on average 10 chops to fell a tree with one blade, and 11-12 with another, you don't try to make the second blade match the first one in time, you simply live with the extra hit or two and at the end of the day you have a simple loss of 15 %.
This a only a real factor when you are rigorously time constrained. For example you are wet and it is raining and you need to get some wood chopped and split in a hurry. However even then you need to be careful not to go too heavy because if you can't maintain the level of exertion your productivity will drop below the 15% and you could end up taking more time, thus you would have been better off to live with it.
The issue now Cliff, is that you support claims of high performance (cutting ability) ...
I have clearly stated that knives with thinner edges out cut thicker edges ones, and in fact have gone into detail about how performance is based on geometry and the types of performance gains you can expect based on changing the geometry. In the review I wrote several years ago on the Battle Mistress there are references to blades which outperform it in several areas, and in other reviews where it is used as a reference the same thing it noted, similar for the Basic comments and in fact true of all the reviews in general.
What I have argued here is that there is a simple give and take on cutting ability and durability (and all other aspects of blade performance in general). As well gains in cutting ability can in fact be made by increasing the edge support when the demands on the blade are high, as I noted in the above for many cases of heavier work. I have also clearly stated that my preference would be for thinner edges. In fact mine would be thinner than yours, significantly so. However, people can want abilities in other areas as I described and I don't think that makes them fools or idiots.
You shouldn't critisize TOPS, then slap Jerry on the back.
Nor should you rant about Busse edges when the makers you note come with vastly thicker edges than you described, which are in fact significantly more acute than the better folders in this regard (Buck and Spyderco). In general I don't let my personal preference define how I rate a knife in another. The Steel Eagle for example has a very aggressive ridging on the handle. This makes it much more secure than the grip on the Battle Mistress, but at the same time makes it much more abrasive. Is it then "poorly" designed? Well that depends on what the user wants. Which is why I tend to focus on what the knife can do and to what extent and let the individuals decide what is right for them. What I demand of a knife will be very different from another user with different physical abilities, skill level, who lives in a different environment who cuts different materials.
200 lbs by the way isn't a large tree. When you pick up a log you only need to lift ~30% of the mass so 60 lbs (with your legs), as you lift from the small end and the center of mass is towards the top so you have a large leverage advantage. You can also static carry on your back huge weights so carrying it is the simple part. The reason that you fail is usually either shear across your chest or failure in your obliques, depending on what work you are used to. Most people tend to fail simply because of the pain in the shoulder as it takes some time for the body to realize that the pain isn't going away and stop producing the signals. It usually takes about a week for me once the season starts depending on how much I do.
TOPS and Ontario by the way made far more reaching claims than Busse, as noted in the above, with no definations at all of what performance they were referring to. As for challenging a makers claims, I agree that makers should be made to live up to the statements they make. Busse however has defined what he means by performance by specific tests, which he has done live and the user can duplicate so I don't consider any hype.
In regards to tomatos and binding, because it is soft it can't exert much pressure on the blade and thus it is easy to cut a tomato even with a thick blade assuming it is sharp. You are talking about grams of force. On rigid materials this can goes up and you are talking about pounds. Specifically there is a high correlation between the material density and the extent of the contribution to cutting ability of geometry.
-Cliff
