More Praise for the Convex Edge

Dave Rishar

Dave Rishar

Joined
Oct 25, 2004
Messages
3,178
Well, I've been liking it more and more and have been adapting all my non-convexed edges to a convex configuration. (Including the blade on my Leatherman.) My one complaint about the process was that it took a while to set up initially, and I'd been thinking about getting a belt sander anyway...

After a trip down to Sears and some setting up, I slapped a 120 grit 1" belt on it, tossed the platen and broke out my two CS machetes (one khuk-shaped, one "heavy") to practice on. I wasn't worried about the possibility of ruining them. While they were handy in their day (before I'd discovered HI, that is) they don't get used anymore, are very inexpensive to replace, and had blades that were notoriously difficult to get a good edge on with conventional methods. The khuk-shaped one, in particular, had chipped out pretty good in areas and would lose more chips if I looked at it wrong.

Ten minutes later, they were convexed and fairly sharp. I finished them off with mousepad strips and sandpaper. They're now scary sharp. Some quick testing failed to produce a chip. I guess there's something to this convex business after all. :)

Afterwards, I couldn't resist - I took a crack at my used-and-abused CS Oyabun. I believe it's actually sharper than it was out of the box now. I guess the belt sander will be part of the process from now on.

Thanks again to the Convex Mafia and in particular, Dan Koster - I would've never even thought to get a belt sander had I not read a slew of informative posts here.
 
"Convex Mafia"


I love it.....let's make Yvsa the official GodFather....:eek: :p
 
I don't have a belt sander, so I've been doing all my convex work with mousepad and sandpaper. Its pretty neat when you get the hang of it and can put a razor edge on a khuk with just the above mentioned items and (in my case) a steel. The downside to this method is that it takes longer and can start to get old if you decide to sharpen more than one khuk at a time.

Bob
 
Big Bob said:
I don't have a belt sander, so I've been doing all my convex work with mousepad and sandpaper. Its pretty neat when you get the hang of it and can put a razor edge on a khuk with just the above mentioned items and (in my case) a steel. The downside to this method is that it takes longer and can start to get old if you decide to sharpen more than one khuk at a time.
Click to expand...

That was exactly the problem I was having. The biggest use of time, for me, was establishing the initial edge. Regardless of the grade of sandpaper I was using, it seemed to take forever to get that first burr.

By using the belt sander, that first burr happens in about a minute - usually less, and I'm going slowly. I use firm pressure at first to establish a good radius and get an easy-to-see burr, then I do the other side. I'll go back and forth a few times using progressively lighter pressure until I'm at the point where the burr is tough to detect, then it's off to sanding by hand.

One sticking point for me seems to be at the higher grades. I can sand for twenty minutes on #800 sandpaper and not feel a burr. The radius looks good, the edge looks good, and all the scratches from the preceeding grade of sandpaper are gone, but I still can't feel that burr. Usually I'll wind up getting impatient and switching to the other side regardless. Occasionally I'll tough it out and get that burr - sometimes so small that I'm not even sure that I feel it - that's when they turn out "scary" sharp for me.

I've seen Daniel Koster's videos where he's slicing paper and...well...I'm certainly not at that point yet. :) I can't even do that when I'm taking my time. Still, it's a goal, and I'm winding up with edges far superior to what they used to be. The belt sander certainly isn't necessary but it cuts a lot of time off the job for me.
 
I was under the impression that you raise a burr on each side with the initial grit sandpaper and use the following grits to polish the edge-like polishing an edge with a fine whetstone after burring with a coarse one. Does Dan burr the edges with every grit in his video like you're doing or is this your personal method?

Bob
 
It's more noticeable if you use a belt sander. If I sharpen by hand with sandpaper and a block, I usually end up "wiping" the burr off as I sharpen.

But you should definitely be raising a burr before you flip sides, regardless of grit.

Eventually, when the burr is loose enough and your grit fine enough, it will "wipe" off. If you can't get it off, run the edge to-n-fro along a piece of hardwood to force it off.

Then a few more passes with a fine grit and you're ready to strop.
 
FINALLY, after numerous viewing's of Dan's video, reading and rereading Yvsa's posts on convex edges, and developing a rather severe case of edge envy, I did it! I was able to get my 15" AK by Kumar to slice paper!! I was so impressed with my new found skill I tried it out on a old machete, and got the same results on that. It's kinda scary watching a 2 foot long piece of steel shave paper like that. Thanks Dan, Thanks Yvsa! Thanks UB for a great forum and great Khuks! Let's see now I have to do the Bura, the Amtak, the ...
 
Glad to hear it, mross!



I must give credit, though, to my first "inspiration".

It was this post by Ankerson that gave me the confidence and desire to study sharpening until I could do the same thing he did - but with a khukuri. ;)

http://www.bladeforums.com/forums/showpost.php?p=2044730&postcount=1


Since then....I feel like I've been a pretty good student of the convex edge....still have much to learn....seems like every time I lift a blade to the belt sander, I'm learning/re-learning the convex edge.
 
may I humbly submit my junior thesis....


http://www.pendentive.biz/blades/kobra4.wmv








I really wish someone would take me up on the challenge to duplicate this cut. It's not hard to do and mostly safe (as long as you are watching).


Maybe some of you new convex mafia inductees could do this (or a similar cutting test) as part of your initiation...? :p


I need to know that the test is not a fluke - that's it's repeatable by others. Otherwise, it's just a gimmick.
 
Daniel Koster said:
I really wish someone would take me up on the challenge to duplicate this cut.
Click to expand...

I could make a video of the box getting knocked out of my hand with a thud.
 
Daniel Koster said:
I really wish someone would take me up on the challenge to duplicate this cut. It's not hard to do and mostly safe (as long as you are watching).
Click to expand...

Hey, I just started doing this a few days ago - give me a little time here, huh? ;)

Today at work, I took the top off a paper drink box with a horizontal cut, using the seax. (This was after a bit of playing around and slicing up a few pounds of tenderloin for lunch...today was a pretty light day, not surprisingly.) The box didn't turn over and remained nearly full. Another cut through an aluminum can was clean and successful but the can tipped over. A third cut through a styrofoam cup full of water was successful but not too clean. She's certainly sharp enough for my purposes.

I'm liking this edge.

After work I fired up the belt sander and got to work on a CS 'hawk, 20" AK, the Rose, and a Napoleon Sword. They all shave now. (The Rose, in particular, is downright frightening.) This just gets better and better.

Again, my thanks.

On a negative note, my left arm is pretty much bald now. :)
 
sounds good to me, Satori....any day now...get some vid equipment....show us your goods. We likes the vids....:D
 
Daniel Koster said:
may I humbly submit my junior thesis....


http://www.pendentive.biz/blades/kobra4.wmv








I really wish someone would take me up on the challenge to duplicate this cut. It's not hard to do and mostly safe (as long as you are watching).


Maybe some of you new convex mafia inductees could do this (or a similar cutting test) as part of your initiation...? :p


I need to know that the test is not a fluke - that's it's repeatable by others. Otherwise, it's just a gimmick.
Click to expand...

Ill take that challenge. I just need someone to tape it.

Give me something harder too, something to get me into the Capo rank of the convex mafia.

I once balanced a segment of 6" black tile pipe on its end and cut it in half. Do you think thats harder or easier than the box cut?
 
Jebadiah_Smith said:
Ill take that challenge. I just need someone to tape it.

Give me something harder too, something to get me into the Capo rank of the convex mafia.
Click to expand...
A slip on the buffer can get you into the capon rank of the convex mafia.:rolleyes: :p :D ;)
 
Yvsa, you're a regular barrel of laughs...capon...thats pretty funny...

Dan, no problem there. Are those spring loaded clamps holding the magazines?
 
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