convex edges

The biggest convex job I ever did was on my Busse FFBM. I used a 1" x 42" belt sander to convert a saber grind with convex edge to a full convex grind. It's a chopping machine now.
Busses015.jpg

FFBM023-1.jpg
 
I've spent the last 5 years going back and forth with how I grind and do final edges. I started doing total slack belt grinding which gives you a true convex grind. Problem is it's too thick to cut effectively. It's fine for thin stock but go 3/16" thick and up, it's nearly impossible to get a good geometry. Another thing, it takes a looooong time to grind a blade. Next I bought the rotary platen. This definately helped but it was killing me to have to constantly replace the platen belt so much. I finally settled on flat grinding first then switch over to the rotary to only slightly convex. I hate to admit it but my grinds are more flat then convex. I'm at 80% flat, 20% convex. I put a very small micro convex bevel for the final edge. I prefer this because of the added strength. I don't trust zero convex edges done on belt grinders. Let me explain, through my testing, I've seen many full convex edges fail because of the final, what I call a "feather edge". It cuts like a son of a bitch but.... if put up against something hard, it will crush. Now this doesn't mean there is anything wrong with the knife or heat treat. It's just that inital edge couldn't hold up against something hard like bone or a knot. These edges usually come from sharpening on a belt grinder. Once you resharpen and get rid of that feather edge, the zero full convex works fine.
One test I do is a bone chop. I use a well seasoned elk rack. If that edge crushes during this test, it's too thin.
I'm kinda inbetween Rick and Andy as far as grind and edges. I prefer that micro secondary bevel edge for reasons I stated above but I've tried to combine the best of the flat grind and convex grind into my main grind.
Scott
 
I've got a similar outlook to Scott:thumbup: I like a 'mostly flat' convex or a flat grind with a convex edge, but even on small knives (bushcrafters) I've found that zero ground convex edges deform quicker in my uses than just about anything. Adding just a slight micro-bevel will increase the edge 'toughness' quite a bit. However, I can send the same knife to Talfuchre, and he'll blend in that micro-bevel to an dang near zero grind and have no problems. I think it actually comes down to your specific uses, and the material that you're cutting. Around here, there's a lot of dirt and grit in the wood from sandstorms, and it's really rough on thin edges, where clean, soft wood would be much less harsh on a knife.
 
I'm not the best person at making things sharp...I'm still learning how to sharpen Convex edges...My Breedens are all Convex edge's & I just got a Landi That has a secondary convex. So Keep up with all this good info. I'm all eyes :D Good looking knives guys !
 
The full convexes are generally 5/32 or thicker blades, yes. I also do a flat grind first- but not all the way and it's probably more like 50/50 than 80/20. It helps set the angle.

thick knives for me fall into two categories- fighters and choppers (MOST combat utility knives are choppers, not fighters). Choppers get a good, variable, strong and sharp secondary bevel. Fighters get time with a loaded and bare strop and possibly a bit of ceramic work on the zero grind. If the edge chips on your opponent's femur then it's HIS tough luck.
 
I'll admit it- I am nervous about convex edges. Especially the polished edge on the Koyote passaround knife I got yesterday. Give me a scandi, hollow, flat or single beel full flat and I'm good to go, but never knew of convex before this forum and do not have that much experience with it. I got subpar results on my BRKT Lil' Bird and Trout when trying to sharpen it again so just took it to the sharpmaker for a swipe or 2 and left it at that.
 
CUTS LIKE A KRIS said:
I'll admit it- I am nervous about convex edges. Especially the polished edge on the Koyote passaround knife I got yesterday. Give me a scandi, hollow, flat or single beel full flat and I'm good to go, but never knew of convex before this forum and do not have that much experience with it. I got subpar results on my BRKT Lil' Bird and Trout when trying to sharpen it again so just took it to the sharpmaker for a swipe or 2 and left it at that.
Click to expand...

If it helps, you can think of it as intelligently "being sloppy" on your angles on a stone :) That doesn't translate to words well. strop bat, strop bat. make or get a strop bat.
 
koyote said:
strop bat, strop bat. make or get a strop bat.
Click to expand...

+1:thumbup: If I were going to point at the one thing that has taken my edges up a notch, this would be it. I just use two sides, one with white polishing rouge, and one with Flitz. Maybe 3 minutes to polish up an edge, remove any remnants of a wire edge, and flat out make a good edge a great edge;)
 
One thing I found for my hunting knife is not to have a polished edge. Polished edges slip off meat and hides. I really like a toothy edge on my hunting knife. A toothy edge will still shave but will also "grab" skin as you run it up your arm. :D It's like your skin is being sucked into the edge.
Scott
 
CUTS LIKE A KRIS said:
I take it you mean a strop attached to a solid backing, instead of a loose strop? If so I have one with green Lee Valley compound and plain finished leather on the other side. Thank you.
Click to expand...

pretty much, yeah. I've got a few I've made, I'm considering ordering one of the JRE ones to see how his leather prep is, though.
 
These are a couple of my "go to" tools when making bevels and sharpening. The one in the foreground is your basic strop bat and the other one is a backing paddle for use with papers or emery cloth. I clamp the blade to the edge of my bench and use it like a file.

Rick

stropbats.jpg


The backcut holds the far end of the paper in place while your index finger grips the loose end.
backingpaddle.jpg
 
Last edited:
koyote said:
This one is hard to describe! it's not a saber grind, not a full convex, and not a scandi.


QUOTE]

yeah, that is basically the older "condor" edge too. Basically, a hard edge to describe.

wanna make a name for it?

canine edge?

CanMand.gif
Click to expand...
 
Gossman Knives said:
One thing I found for my hunting knife is not to have a polished edge. Polished edges slip off meat and hides. I really like a toothy edge on my hunting knife. A toothy edge will still shave but will also "grab" skin as you run it up your arm. :D It's like your skin is being sucked into the edge.
Scott
Click to expand...

There was an amazing article in TK, a long time ago, by I think John Larson, but I'm not positive. In it, he gave these alaskan fisherman the same knife both polished and toothy, and they liked the toothy edge more, saying the super scary sharp knife didn't cut right. It was very interesting.
 
How many of the makers have used scotchbrite belts for sharpening? I use two, medium and fine. I load the fine up with white compound. I've tried the 2X72 leather belt on the grinder and wasn't impressed.
If anyone uses a little 1X30 belt sander for sharpening, try silicon carbide belts. They sharpen better and last longer then aluminum oxide belts.
Scott
 
Joezilla said:
There was an amazing article in TK, a long time ago, by I think John Larson, but I'm not positive. In it, he gave these alaskan fisherman the same knife both polished and toothy, and they liked the toothy edge more, saying the super scary sharp knife didn't cut right. It was very interesting.
Click to expand...

Those guys are right. Fish are probably worst then game for being slick. I know from experience, close to 30 years of deer hunting, toothy is much better.
Scott
 
Gossman Knives said:
Those guys are right. Fish are probably worst then game for being slick. I know from experience, close to 30 years of deer hunting, toothy is much better.
Scott
Click to expand...


I must agree, as much as I like a polished edge for most cutting chores, a toothy edge (like on Bob Dozier’s D2) is the best I’ve used processing game.






Big Mike

”Scaring the tree huggers.”

Forest & Stream
 
You must log in or register to reply here.
Back
Top