What is the toughest type of knife grind?

[marcinek]

Or this

http://brkca.com/convex.htm

"DO NOT apply much down force on the blade; the weight of the blade is sufficient to do the job. Press too hard and the abrasive will actually be coming back up in the wake of the blade and remove the edge, dulling the knife rather than sharpening ."

i.e. rounding off the edge...which you don't want to do.

 

[hermit dave]

Yup.

f1 and f2 are curves that meet at P. The tangent to f2 at P is t2. The tangent to f1 at P is t1. t1 and t2 meet at an angle that measures phi. That is how science and mathematics defines the angle the curves meet at.

I mean, I'm sorry if math ruins everybody's fun, but you cant say 2 + 2 = 5 or a pentagon has 8 sides if you don't like it.

Sorry, but that's the angle of the intersection. It is not the included angle of a convex edge. Besides, most convex blade grinds have an increasingly smaller radius as it approaches the edge. You diagram shows a consistent radius.

 

[FortyTwoBlades]

Sorry, but that's the angle of the intersection. It is not the included angle of a convex edge. Besides, most convex blade grinds have an increasingly smaller radius as it approaches the edge. You diagram shows a consistent radius.

It actually is the included angle of the convex edge. Regarding the diminishing radius as you approach the edge, that's on a micro scale, in which case literally every single edge is a convex with an angle of 180° because it's dead flat at the very apex, regardless of if the bevel appears flat or convex at a macro scale.

 

[FortyTwoBlades]

Note also that the curves can be as complex as you like and you can still measure the angle of their intersection.

[video=youtube;afkj7mPJldc]https://www.youtube.com/watch?v=afkj7mPJldc[/video]

 

[hermit dave]

So your diagram is showing approximately a 100 deg included angle for the convex edge. Try grinding a flat edge at that angle, and you will have a useless cutting tool.
You're just measuring air in your diagram.

 

[trevitrace]

Cold steel.

 

[marcinek]

So your diagram is showing approximately a 100 deg included angle for the convex edge. Try grinding a flat edge at that angle, and you will have a useless cutting tool.
You're just measuring air in your diagram.

Its. A. Diagram. Its for illustration. I could have used a 20 degree included angle and the result would have been exactly the same...except you couldn't see it.

Its like you are saying that 2 > 1 doesn't establish that 3,000,000,000,002 > 3,000,000,000,001, because the numbers are too big to visualize.

Really, you are free to convince yourself of whatever you like, and I am glad your conclusions make you happy. Really.

 

[FortyTwoBlades]

So your diagram is showing approximately a 100 deg included angle for the convex edge. Try grinding a flat edge at that angle, and you will have a useless cutting tool.
You're just measuring air in your diagram.

Both geometries (flat AND convex) in the diagram have the same edge angle. Change the angle on both in tandem and it does not alter the geometric relationship between the two. It just becomes harder to see because you're reducing the visual space between them. The fact that he chose such a broad angle to assist in visibility does not in any way impact his assertion. It's merely a visual aid.