Singularity :
The very experience you want to design in the beginning shows that you are more interested in edge holding than in sharpenability, edge efficiency (ability to penetrate), or even ease of use of a knife.
It could simply be the first thing he intended to look at. The first thing that I do when I get a knife is measure its NIB sharpness, however this is last on my list of what makes a high performance knife.
Are knives designed to cut only rope, as it seems THE test to do ?
It is done mainly because it is very easy to get a lot of rope cheaply which is very consistent. It has a lot of great characteristics though for looking at knife performance as it is both resistant to being cut into and resistant to being deformed so it allows you to look at both aspects of cutting ability (rupture and binding), as well as push cutting vs slicing. Cardboard is very good as well, I don't do a lot of it simply because I don't have access to it.
... will a knife that cuts rope well, perform on beef, horn, wood, plastic?
Unless the edge strength is exceeded and it breaks apart, the basic geometrical effects are the same for all materials so yes. What changes are the compressive strengths and hardness of the material which adjust the influence ratio of the rupture resistance and deformation (how hard it is to start the cut, and how hard it is to continue it as you have to wedge the material apart). For example cheese is very soft and easy to cut into, but wedges tightly onto a knife. So a thin blunt knife can slice cheese better than a thick sharp one, and the opposite will be seen on rope.
Since most rope cutting is done on narrow cord, the primary grind doesn't have a significant effect (Busse is one of the few people that cuts full one inch rope). A blade with a very shallow sabre hollow grind and a thin edge, can cut thin rope very well, better than a SAK say, but not perform nearly as well when slicing pine, as you get 2-4" of penetration there and a thick primary grind will wedge badly, especially the "t" shaped hollow grinds. Of course they are the same basic principles as what is found in the rope cutting, so once you do a lot of it you can extrapolate it to other mediums and predict the performance based on how hard they are to cut and how badly they wedge.
You can also adjust the depth of the cut to focus the performance on the aspects you want to examine. For example thread looks at sharpness, 1/4" poly at sharpness and edge angle, 3/8" hemp at sharpness, edge angle and edge thickness, 1" hemp at sharpness, edge angle and width and primary grind characteristics. I use wood instead of 1" hemp as it is cheaper (I have a lot of it at hand). Lots of other materials should be included as well of course to examine the effect of different properties, for example cut thick vegetables. They are very soft so they are easy to start a cut, but are very elastic and stiff so exert a lot of wedging force on a blade.
... edge-holding on rope can be extrapolated to represent edge-holding in general?
Edges blunt by rolling , wear, fracture, indentation and corrosion. Rope is mainly rolling and then wear, with light indentation (its not real indentation the edge just rolls until it is at 90 degrees). All materials which have similar behaviour can then be expected to behave in the same manner. You could include corrosion resistance by cutting wet rope. Some materials are very different yes. For example used carpet is heavy on indentation and wear resistance with rolling as well. However wood induces little wear but a lot of rolling and heavy impacts so fracture is a real possibility. It is easy to see that two blades could have different relative edge holding ability's on carpet vs chopping wood (M2 at ~66 RC vs 52100 at 60 RC for example).
Which edge holding are you talking about, slicing or push cutting?
You can look at both on rope, since they are dependent on similar characteristics you can extrapolate one from the other. I use slicing mainly because push cutting takes longer to do. There are some complications as I mentioned in the other thread (listed below), but these are not first order effects.
Is slicing edge-holding correlated to push-cutting edge-holding?
Yes since it is dependent on the same characteristics. Again there are some complications as with everything, a the recent thread which deals with one such example :
http://www.bladeforums.com/forums/showthread.php?s=&threadid=214104
How do you ensure the sharpness state is the same at start?
You measure it.
You could say that you could design tests for all or most parameters. I'll reply that you'll never know all parameters ...
It is a wedge, it isn't that complicated a tool.
... and that if you take the most importants and rate them, you still do not know if a knife that scores great for all tests is a good knife. In this the human factor IS the key, and surely like our tastes are different, appreciations changes from human to human.
Yes there will be varied opinions as different people put different weights on different aspects, which is why you don't just list the conclusion but what it was based on, what were the criteria used and how did the blade perform at those tasks. It would of course be optimal if the reviewer actually avoided such conclusions, promotional or otherwise.
To clarify, there was no argument being made that all you do is a some rope cutting and then you have a 100% all inclusive view of knife performance. However from looking at how a knife cuts into a piece of rope (when you have done it with many other knives and a lot of other cutting on other materials to correlate the performance), you can form an informative opinion on how it will cut in general.
Baliswinger :
No amount of review reading can compare to how you feel about it.
No of course, reading what someone else has written should never replace personal experience, it should just be complementary.
-Cliff
