Okay, I'm Sold on Convex Now

Dave Rishar

Dave Rishar

Joined
Oct 25, 2004
Messages
3,178
I don't know what happened - maybe it was the phase of the moon, maybe it's the temperature outside, but I decided to take a crack at putting a convex edge on the AK Bowie utilizing the sandpaper/mousepad technique.

Whaddya know...it worked this time. Never did before, but this time, it worked.

I tried it again on the Seax. It worked far better that time. It chopped cleanly through paper! Not every time, but sometimes. (Which is far sharper than any other knife I've ever owned.) Against thicker paper, like envelopes, it sliced through every time.

Of course, I had to redo the Bowie after that. It slices paper now as well.

Then the Rose. Then the 16.5" AK. Then the blade on my Leatherman. (I should've started with that, in retrospect - it took all of four minutes to do.) I think I'll take a break for the rest of the night, but the rest of them are going to get one too.

Very strange - they don't feel "sharp" to me, the way I equate sharpness with feeling...probably because I didn't actually know what "sharp" felt like. :rolleyes:

The weirdest thing about it? The closest thing I can equate it to is riding a bicycle. It seems physically impossible until it clicks...then you're wondering how you didn't see it earlier. This is so much easier than grinding a secondary bevel on.

Obligatory thanks to Dan Koster, Yvsa, and the rest of the Convex Mafia. ;) Without the instructions and discussion, I would've never even bothered.
 
Now start practicing the one hand clapping thing.

Bruise can show you how...
 
Heh, told you so. :rolleyes: :p :D :)
And like riding a bike, once you learn how you'll never forget. Your knives will never need be dull again, ever! :cool: :D
 
I'm starting to get it too. It seems so superior because when you look at it, the convex edge doesn't seem sharp, but boy, is it sharp!! I haven't tried reprofiling any khuks, I'm speaking from very limited experience. I am thinking I'll get the $39 Harbor Freight 1" belt sander and try my hand with some beaters and throwaways and then use it to put a real edge on. The sandpaper and mousepad technique works but it uses up a lot of sandpaper and takes up a lot of time. Maybe OTOH I'll get some more sandpaper and just stick with that awhile...hmmmmmm.

Good post!
 
Man, but it takes a while... especially when a diamond freshens up a damaged khuk edge so quick.

must get 2x42 grinder- uses both size belts, no?. And not the HF cheapie. Their S&H charges make me look elsewhere.


Ad Astra
 
Satori said:
Very strange - they don't feel "sharp" to me, the way I equate sharpness with feeling...probably because I didn't actually know what "sharp" felt like.
Click to expand...
I still remember when I got my first HI khukuri, a 15" Ang Khola. It had a nice convex edge. I was showing it to my cousin, a lady in her 50's at the time. I watched in horror as she put her thumb on the edge of the blade and ran it down the length. A nice long stroke to the end of the blade. At first everything seemed OK, but then the flesh of her thumb opened up like a flower and blood started to flow. Her first words were "It didn't feel sharp!" I don't think she ever felt the cut (until later) and her reaction was more embarrassment than anything else.
 
I remember trying all kinds of expensive sharpeners on my first khukuri and just about giving up. I decided that getting the right angle was impossible for me.

Then in desperation I tried the method Yvsa and Dan kept extolling and wow! Not only did I get my blades shaving all along the whole edge, but it was not hardly any work to KEEP them shaving! Now except with folders I have been trying to buy or put a convex on everything. So much easier to maintain and more durable!
 
it was not hardly any work to KEEP them shaving!
Click to expand...

This, for me, is its greatest asset. The convex edge is easy to maintain, provided you don't abuse your knives.


Congrats on making the leap, Satori. Welcome to the Realm of Scary Sharp.




By the way...you don't need a sander to put on a convex edge. You can always make a convex micro-bevel. I'm going to be showing this on the new CD.......oops....:eek:
 
Is anyone suggesting a convex edge is 'sharper' than other profiles? Can't be. This whole matter of feeling sharpness is interesting though.



munk
 
munk said:
Is anyone suggesting a convex edge is 'sharper' than other profiles? Can't be. This whole matter of feeling sharpness is interesting though.



munk
Click to expand...

I agree with you munk. i don't think the covex is so much sharper as it is smoother. I know when i used to sharpen knives to a full flat grind the sharp toothiness is what i was feeling for. Baiscally, i was cutting with a razor sharp bur and not the real edge. The convex method seems to polish away that bur leaving only a nice smooth edge that slices rather than saws or catches. That's why, IMHO, that it's easier to cut yourself with an convex edge as you feel it for sharpness. The toothiness is gone and only the highly polished edge is left. What do the sharpening experts think?? any validity to that?

Jake
 
Steely_Gunz said:
I agree with you munk. i don't think the covex is so much sharper as it is smoother. I know when i used to sharpen knives to a full flat grind the sharp toothiness is what i was feeling for. Baiscally, i was cutting with a razor sharp bur and not the real edge. The convex method seems to polish away that bur leaving only a nice smooth edge that slices rather than saws or catches. That's why, IMHO, that it's easier to cut yourself with an convex edge as you feel it for sharpness. The toothiness is gone and only the highly polished edge is left. What do the sharpening experts think?? any validity to that?

Jake
Click to expand...

I'm not an expert or even a smart novice but when I see a convex edge it doesn't look like an edge and when I feel it, I don't feel an edge until I get to the actual edge, if that makes sense. With a non-convex edge I can see and feel a bevel and I say to myself "that's sharp!". With a convex edge, I don't feel the bevel, it's just smooth curve, so I assume it isn't sharp. I don't see the edge either, I just see smooth curve, so I say to myself (if I don't know better) "that isn't sharp!!"

I think has a lot to do with not being able to know a convex edge is really sharp!
 
munk said:
Is anyone suggesting a convex edge is 'sharper' than other profiles? Can't be. This whole matter of feeling sharpness is interesting though.
munk
Click to expand...

To me both kinds feel sharp. Like you say I don't think it's any sharper, just easier to get sharper that way, especially with all the bends and irregularities in the edge from hand forging. I do think at least on the ones I have done that the convex one doesn't stick as much cause of the polishing
 
convex is an edge geometry, not a degree of sharpness.


sharpening, simply put, is polishing.


All blades are somewhat polished....all blades are somewhat toothy.

To what degree you polish, matters only to you.


I have shaved hair with a convex-ground khukuri fresh off a 120 grit belt. Polished? Nope....quite toothy actually. Sharp? Oh yes.
 
Re: feeling sharpness


A flat-ground blade will always have a slight burr - unless stropped. Many folks mistake that for "sharpness".

If you run your finger down a blade for sharpness.....you're a.......well, let's just say you might be making an appearance on the Jeff Foxworthy show soon....:D

If you need to slide something up and down the blade, use the edge of your fingernail to check for "smoothness".

A polished blade will have no burr.....
 
I always run it very carefully down the side of one of my fingers that is real calloused, if the edge cuts into that callous and can slice a thin layer off it is sharp.
 
My convex edges feel sharp.:D
That is when they're sharpened to perfection, takes a while sometimes to get them that way.
But you have to remember that I've been doing convex edges as long or sometimes much longer than some of you have been alive.:rolleyes: :p ;)
 
Is it possible to use a flat stone to put on a convex edge? I have seen a belt
sander described and a mouse pad method, both seem to take advantage of the
inherit "give'" to achive the convex edge. Can you do it with a flat stone? I am
intrested in this as I usually sharpen with my coarse and fine stones I bought
from the Razor's Edge site awhile back.
 
mross said:
Is it possible to use a flat stone to put on a convex edge?
Click to expand...
Yes. Just rotate the knife and its edge on the stone. People have been using flat stones to put convex edges on knives since metal knives and flat stones have been around.
It's unnatural to put a beveled edge on a knife. Anyone left to their own devices will automatically put a convexed edge on a knife because they haven't heard all the ballyhoo about sharpening knives.
 
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