Convex Edge Better by What % ?

@bluntcut
I take it that you are a convex over v. ?
C over V in the D2 scenario?

bluntcut said:
How you grind the convex bevel will affect the outcome. From a cross sectional of a V edge bevel - let's call this area X. When convexing - are you?
1. Keep same area X and bevel height (i.e. convert line to Bezier curve, while keep same integral area)
2. Keep same area X but with +- bevel height
3. Decrease area X and keep same bevel height
4. Decrease area X and increase bevel height
5. Increase area X and keep same bevel height
6. Increase area X and +- bevel height

In addition, convex/curve control points also has major performance impact.

IME (BM Pardue D2 & high rc D2 knives made by me) - high likeliness that a super sharp D2 with 44* inclusive edge bevel against dry oak = bunch of large chips. A micro-bevel of 54+* inclusive may alleviate/mitigate chipping problem. OTOH, D2 Outcast low RC may has enough toughness for chopping impact.
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" A micro-bevel of 54+* inclusive may alleviate/mitigate chipping problem"
I should do this, thanks.
 
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allout, you grasp my point. I am not clear on exactly what you don't like about your blade presently, so I am not sure what to suggest for you. But as blunt suggests, if the bevel goes deeper the cutting will be finer, though perhaps not as durable.

D2 is tough stuff, though, and regrinding it to raise the bevel further takes a little time. (I know, I've been working on my new BK24 for a couple weeks).

What exactly don't you like about your edge presently? What doesn't it do that you want?
 
In the 80s the big debate was .357 vs .45 and .223 vs 12 gauge buckshot (mostly for leo use). Personal opinions and war stories were flying. There were many experts and veterans with combat experience on both sides. The math of terminal ballistics ended the debate for many if not most. It came to mind during a post about grinding the back of a D2 Outcast that this math might be useful in sorting out the actual differences between a flat and a convex grind.

The Outcast was put in a tough spot as it was working with an Ontario Machete which was serving as a point of reference for the testing of several blades. See post #5 for details.
http://tinyurl.com/mzte2cj

It is likely that many would say convex the edge and it would work better. There are a bunch of variables at work here, like where on the curved blade it was striking the wood, cut technique (bowing to the target) and so on. It just seems that this is another situation that is mathable.

The Outcast is probably too light and too short, despite the edge type or blade coating for that matter, to do this sort of work effectively. Which is a shame because it is a nice knife and the handle when used with a lanyard is a pleasure, and is effective at reducing the vibration.
 
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Math (my first love) is a wonderful and useful thing. But to use it well, you have to discern what things you want to measure, and what things don't matter (and also, what things matter that perhaps you can't measure, but I digress.....)

In any specific situation you may be able to measure or control all relevant variables. But slicing meat, chopping wood, skinning, cutting phone book paper... well, the variable start to multiply. Sometimes, human common sense saves time and works better than math. (And 12 gauge buckshot is better than .223, and .357 is better than .45 --- sorry, just couldn't resist....)

You are right in the observation that the size and balance of the knife may matter more than the edge.

I think a good convex edge is a thing of beauty. But they are not easy to do which is why we all don't have several.
 
The buckshot was OO vs .223 FMJ. The pistols were relatively the same type of bullets, .357 mag and .45 ACP, and both were hot loads.

Solving for which one put the highest amount of useable energy into a human target at 21 feet. No body armour...lol

Example: Imagine the guy in post #41 coming at you with a large kitchen knife that has a convex edge from 21'...:ghost:




@pmeisel
Does your math mind give you a gut feeling (the ability to sense) that one or the other (C vs V) has a mechanical advantage?







Nowadays it is like Po-Po Pinball - they see how many times they can fire before the target falls; with their big .40s:numbness:
 
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Maybe it is time to call in the professionals, maybe it time to call the Mythbusters
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My guess is that there are hundreds of posters here with more expertise on edge geometry than anybody on a television show.
 
allout said:
V versus Convex


I hope this does not end up as another one of those nightmare porn math / spooky physics phenomenon things. Hahaha that might not be so funny…


Warning: If you have not seen the “Double Slit Experiment” stay away! (XXX). Seeing this “spooky physics experiment” or not seeing it may well alter who or what you are.:yawn:
[video=youtube;DfPeprQ7oGc]http://www.youtube.com/watch?v=DfPeprQ7oGc[/video]



@ nerverdie Well Said



I wonder if V vs () in chopping it is more of terminal ballistics math and in slicing it is more an aerodynamics math? Or maybe math is just math like people are just people...








[video]http://tinyurl.com/ofzd5w9[/video] RIP:thumbup:
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Isn't physics great? Just when you think you know it all, you realize you know almost nothing. Honest scientists are humble scientists...
 
Gut feel, the convex edge will be easier to keep sharp, and be a little more durable. Not necessarily cut better first slice, but maybe better over time.

I'm about to spring for a Ken Warner convex, always wanted a good one.
 
When comparing performance it's important in my opinion to keep effective edge angle constant. This would mean that a convex edge of equal effective edge angle to a V or linear edge would actually be thinner, though the visual bevel width would be increased. You would essentially be knocking the shoulder transition off and blending it in. This increases cutting performance while keeping edge angle the same. One must approach this in one of two ways and stick with it from a debate standpoint--are we talking about two identical knives built from scratch from the same stock but ground differently? Or are we talking about converting a knife from a linear edge to a convex? Either way, for a given effective edge angle, a linear edge will actually be the one with more material behind it--not the convex. Though you can make a convex with more material behind it than a linear edge, you must also increase the edge angle, rendering the comparison moot because a linear edge of this increased edge angle would be even more robust.
 
@42
It is nice to see the thinking behind the “Special Grade”s that you offer on your blades. It is also a good example of how diagrams would enhance a train of thought. I did have to read your post more than once, it is quite a bit of information to digest. Could we get the bullet points summary, for those of us who do not have a convex mind?
 
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