Sharpness in context

[Dog of War]

IMO one good reason for striving for a very high level of sharpness is simply that it's an excellent indication that you did everything else correctly in the sharpening process: no wire edge or damaged steel remaining, entire edge even, etc. Also the blade that starts the sharpest usually will remain sharper longer.

As far as those half atom thick edges .... doesn't the explosion destroy the blade, you, and the surrounding area?

 

[hardheart]

I‘m not really sure carbide size and volume really has much effect on thick, thin, polished, or coarse edges, unless your edge is a good deal under 10 degrees per side, and I’m not even sure about that. I believe very few are that thin on pocket knives like we all use every day. There has been a lot written about carbide volume and size and theory about it but you know what they say about theory and then there is..

I think it would have to, if we are getting our edges anywhere near those shots taken by Verhoeven. With a micron wide edge, carbides of just a few microns in size are going to have a chance to get pulled out in work. I don't know if this is quite right, but it's how I visualize it-

if the edge is a micron wide, the nice round carbide can't be much wider at whatever angle I put on there, but one I'm sure is >10. So, for 20 micron carbides or larger, they would protrude from the softer matrix near the edge, and short a distance away from it as well even if they manage to stay in the center of the cross section. Plus any large carbides away from center are going to protrude further from the surface, as they don't wear away as quickly as the surrounding martensite.

 

[gunmike1]

IMO one good reason for striving for a very high level of sharpness is simply that it's an excellent indication that you did everything else correctly in the sharpening process: no wire edge or damaged steel remaining, entire edge even, etc. Also the blade that starts the sharpest usually will remain sharper longer.
QUOTE]

That's what I do, and since my knives are so thin I go for edges brought up to at least spyderco fine and usually ultra fine lately. I carefully monitor the edge formation with my trusty Radioshack lighted scope, and my edges have been sharper and longer lasting once I figured out how to get rid of those pesky burrs. Plus, since I carry at least 2 and usually 3 knives, I can always leave one with a little rougher finish for any larger amounts of cardboard or rope I run into. I have found though that for my EDC needs even a thicker (15 per side or so) edge at a very high polish holds a shaving edge just fine for several days, as I don't generally run into marathon cardboard sessions. I mainly open letters, some packages, cut some food up, all kinds of stuff. After carrying the passaround Caly 3 in SE I think I need to carry a SE knife for my cardboard and rope and other tough chores, so I can keep the rest of my knives with the nice, sharp, polished, long lasting showoff edges that I like.

 

[redhawk44p]

Of course, one can have a blisteringly keen edge which not only whittles hair

Here is a little hair whittling.

 

[Bors]

A super sharp edge is ony part of the cutting picture. The grind angle, type of grind such as flat, hollow etc.., width and thickness are just if not more important than that 1 micron super polished edge.

When a blade passes through a medium it's like a wing passing through air. The first layers of the medium compress as they are cut. As the blade passes deeper the medium compresses and friction and pressure on the blade increase.

For a design to cut well the medium must flow over the blade. The better the flow the easier the blade will pass through. A good example of poor flow would be a narrow thick saber hollow ground blade.

With this grind the medium must compress at a very high rate over very short distance this creates a lot of friction or drag. A slightly better grind on the same blade would be a full width flat grind. This spreads the compression out over a longer distance allowing for a somewhat deeper cut. A even better grind would be a a full convex from edge to spine, this allows for the medium to compress and then relax as the blade passes. But again these are only examples not absolutes as medium consistancy has a lot to do with the picture also.

So before you get all frustrated because that hair popping edge doesen't cut well you may want to look at the grind profile vs. what your cutting.


Bors

 

[Cliff Stamp]

.... I also believe the dichotomy between sharpness and cutting ability resolves when sharpness is measured in the context of what's being cut and how it's being cut.

I think this lack of distinction was and continues to be one of the major source of confusion in regards to knives. I agree that the functional benefits of sharpness decrease significantly as you pass a certain point, but I also believe that most people don't appreciate sharpness simply because they are used to using very dull knives. Take a random knife from someone and cut a piece of 3/8" hemp on a draw and measure the force. Properly sharpened with the optimal geometry this is about 5 lbs. I can guarantee that you won't get anywhere near that with most knives and that if you show someone the difference between a sharp knife and one which has an optimal geometry then the difference is clear and easily known.

-Cliff