Edge geometry

I posted this is another thread, but didn't get a response. I finally did an edge map on my latest blade (now back from HT). Given the style of knife (Bowie-esque), are these numbers close? I realize I have some work to do to flatten the ridges, but does the progression seem about right, especially near the edge? I've noticed some of you pushing MUCH thinnner edges.... but on a Bowie style? What should be my target numbers?

Trench8.JPG
 
It would be nice to see where a .020" line would be. How thick it the spine?

Rick
 
Spine is 0.25". The 0.02 line is about two thirds of the way from 0.05 to the edge, I think.
 
Sorry Tryp, I was talking about the way the small back clip transitions into the spine. I know it was part of the design with the pin-up knife.
 
Oh that. Not planning to do anything about that. I like the way the curve of the spine carries forward into the pseudo-swedge. A sine-wave kind of effect.
 
Ok maybe it was from the picture or that you still have some cleaning to do on it but it didn't look "finished". Can't wait to see it all done. :thumbup:
 
The “edge” is just a concept of,… where one thing stops and another begins. The “boundary” between the two. The edge has no mass of it’s own. It’s just an “idea”. So,… what we are talking about is really what’s behind the edge.

The blade.

It seems unfruitful to try and have a discussion about edge geometry, (the edge has no geometry of it’s own, but follows the geometry of what‘s behind it), without talking about the entire blade.

I think most people do it intuitively as opposed to formulaically, in the long run…
 
Good input. Since I don't have enough experience with large format knives (or any sort for that matter) to have developed a real intuition, I was more inclined to rely on a more quantitative approach. I'll just keep working it until I am happy... then work it some more, assuming I am too easily pleased. ;)
 
Tai Goo said:
It seems unfruitful to try and have a discussion about edge geometry, (the edge has no geometry of it’s own, but follows the geometry of what‘s behind it), without talking about the entire blade.
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Which is the point (ho ho) of the thread. Then again, as long as we're picking nits, a point is also infinitely small as well so in fact it doesn't exist either... :rolleyes: How many angels can dance on the head of a pin, anyway? ;)
 
To me,... the whole blade is the edge.

It's hard to talk about the "leading edge" of a blade without talking about what's behind it.

It's the overall package... In essence “the edge“, or boundary between the blade and something else, goes all the way around the blade in every direction. The “leading edge” is the edge on the working side or end. I think this is important to understand about knives.

The closer you can get the leading edge to vanishing into nothingness,… the sharper the blade will be, but how well it cuts will depend on what's behind it...
 
this is more to make the maker think about that form and what the edge/blade is made to be useds for as all uses have "maps" that work better then others

i think in this case the "map" is better at showing a bit of wave down the blade (kind of 2 inch belt geind but way softer ) maping is a tool liek hardness testign as one persons ideal is garbage to another but we all learn a bit from it in how we want ot work
 
I dont think there is an exact answer as different makers are going to set different standards for what they are going to chop etc. Going through some "soft" pine 2x4's is an entirely different and much easier task then getting through some thick wall dried bamboo for instance.

I will say this, once you figure out what thickness/geometry works for you- take a thin (1/8") piece of brass stock, grind a bevel across the top edge, then press your favored convex edge down into the brass. This will give you a "cut" into the brass giving you something to quick check your other blades by.

Personally on most of my big knives the edge is thinner back toward the choil, and gradually gets thicker toward the point. Then when I roll the convex in I put a steeper angle toward the tip to give it even more impact strength. The further out on the blade you go, the more impact stress the edge has to take.
 
I must agree with Mr. Wheeler here. When I first started off, my tendency was to leave the edge too thick before I started trying to convex/sharpen it. To my eye, there was no way that you could go so thin and still have it hold up.Needless to say, I ended up with some cold chisels, as Mr. Caffrey so eloquently put it.
NickWheeler said:
I like to chop through steel drums and drop the blade tip first into concrete from 120 feet up. I really have no idea what all this "thin edge" talk is???? :confused: :confused: :confused: :o ;)


I had made several knives early on where I focused on trying to make them look and feel well made, but was scared to grind the edges very thin because a.) I knew I'd screw them up, and b.) there seemed to be a lot of talk about ruining blades by grinding them too thin and "ruining the temper."

Then one day I tried to cut up an apple with one of my hunters. It was more like driving a splitting maul through wood than it was like slicing an apple. It was at that very moment that I realized just because a knife looked pretty decent and had a professional heat-treat (Paul Bos at the time) didn't mean it was a good knife.

I keep getting them thinner and thinner ever since then.

I think there are a lot of people that think just because a knife doesn't look super thick at the edge with a huge secondary bevel, that it's thin---- but if the blade is over 0.250 thick at the spine, and the bevel only goes halfway across the width of the blade, and there's no distal taper--- it's still a thick knife.

And I'm definitely with Ed on this--- it kills me when I see a photograph of a $5,000 folder and it's got a secondary bevel on it that should be on a camp axe. A knife like that could (and should IMHO) be almost a zero edge. Not only does it show the knife isn't really very functional, it completely takes away from the art in the piece as well--- It's like seeing a beautiful, tall, slender super model--- with a giant, harry, beer-gut sticking out over her bikini. :eek: :barf: It just ain't right. ;) :D
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