Convex Edges and Fallkniven

[Rebelder]

I'm having a slight disconnect with this - I understand that many advocate, some even necessitate, using a flexible backing/sandpaper and and a strop for sharpening convex edges. However, I see that Fallkniven, which produces knives with convex edges, sells diamond stones for use with their knives and recommend using diamond and ceramic for sharpening them.

It's implied that in an outdoors and survival situation, stones are all one would need to properly maintain a convex edge - no mousepad/sandpaper and strops are necessary.

I'd be interested in hearing from you guys with more field experience with convex edges.

 

[udtjim]

For me, it's hands down the sandpaper version. I have no doubt that I could keep a convex sharp with a stone but the sandpaper just works to good for me to change. Once in a while, I hit them with the belt sander it they get to thick.

 

[kgd]

For maintenance a loaded leather strop works great. Personally, I think the mousepad/sandpaper works better when you are profiling the entire bevel. When just sharpening the edge I usually just use the strop. Using a stone, you will sharpen like you would a V-grind. Most of the folks now recognize that any freehand sharpening essentially produces a convex edge because the slight variations in holding the edge angle. The unaided hand can never be perfectly true.

Like the case of sharpening a V-grind, you want to keep your angle as constant as you can and have the correct angle where essentially just the last mm or less of the edge is in contact with the stone while at the same time not having the angle of the knife held to high too produce an obtuse edge. In the end, the main issue that people have with using a stone to sharpen is finding the correct angle height (spine relative to stone) to sharpen and being consistent at it. With a flat stone you need to have this as accurate and as consistent as you can.

With a softer surface like the mouse pad you purposely use a much more shallow angle between spine and the surface of the sandpaper and then press slightly so that sandpaper depresses around the convex portion of the blade to the edge. For this method, the angle accuracy is less important but the key is finding the right amount of pressure. Too much pressure and the sandpaper will wrap up over the edge of the blade and dull your blade rather than sharpen it.

A leather backing provides the same action as the mousepaper. Because it is stiffer you want to use an intermediate approach. The angle of the spine relative to the mousepad is shallower than you would us for stone and wider (higher?) than what you use for the mousepad. You use a bit more pressure on the leather because the backing does not produce as much flexibility in wrapping the edge around the convex belly. Same principle though, too much pr essure and you dull the edge.

So basically you can use stone, mouspaper/sandpaper or leather/sandpaper for sharpening your convex edge. You will vary your technique somewhat with each approach. Then follow up with a loaded strop for the final polishing.

In most cases, if you regularly tune your blade, the stropping is what you use. The sharpening is what you use with more extended dulling or long trips or for taking care of damage like chips in the edge.

Edit - Uditjm - forgot all about the loose belt sander method....That works well too!

 

[baldtaco-II]

“no mousepad/sandpaper and strops are necessary”

All hinges on the word necessary. You can take any convex you like and sharpen it on a hard flat surface and get a good edge. On that, you have satisfied necessary. In fact there is a school of thought that says that all freehand sharpening on a flat stone forms a kind of convex edge because of the accrued errors. Perhaps, but that's not a nice convex in the sense I think most of us mean it. Although it can be done nicely freehand with the application of effort.

Personally, I find the easiest way to get an optimal convex is to use a compliant backing of some sort. But then we have a mix of “easiest”, “optimal”, and “necessary” that makes for a woolly brew. My conclusion is that it is more useful to say “a hard flat surface can be sufficient for maintaining a good convex but it is not the optimal route for me”.

 

[SpookyPistolero]

This probably isn't the 'approved' method for doing so, but I've used a stone on many convex blades when I'm out & about. I just move the blade backwards (dragging the edge, not pushing the edge) while slowly raising the spine so it sharpens along the whole bevel to the edge. Then repeat for the otherside, etc. Then strop. Seems to work fine for me without any negative effects on the bevel or edge.

But now I pretty exclusively use a little altoids sharpener I saw Riley use, with a mouspad chunk on one side and leather piece on the other. It'll sharpen, reprofile, strop, etc. and weighs nothing.

 

[kgd]

Magnussen uses a belt sander to produce the convex edge and then finishes the edge with stones. His edges are thus far the sharpest I've ever encountered. I seen lots of blades in my days and attended a few shows now. He gets 'em sharp!

 

[Bushman5]

I use sandpaper (3m wet dry autobody paper) and mousepad, then finish with a 8000 grit ceramic stone.

 

[Ravaillac]

"Refreshing" convex edge with flat stone can be done without much problem.
I generally use the stone, notably small Fallkniven stones, as I wood use a file on an axe. Axes have been convex from centuries long before belt abrasive where available, convex edge on japanese swords is done using a stone.
Last but not least, adding a small bevel on top of convex grind won't drastically change properties.

 

[raylaconico]

You can sharpen any type edge with whatever you have, either stone, sandpaper, ceramic, or diamond. You can use whatever you're comfortable with and get good with. Different people like to use different things. IMO, there's no right or wrong way.

 

[Gossman Knives]

When you sharpen a convex edge all you are hitting is the very edge. It's done at a higher angle then a conventional V-bevel. I use rods and flat diamond sharpeners exclusively for convex edges. Then strop.
Scott

 

[Dannyboy Leather]

Post expired.

 

[rifon2]

Magnussen uses a belt sander to produce the convex edge and then finishes the edge with stones. His edges are thus far the sharpest I've ever encountered. I seen lots of blades in my days and attended a few shows now. He gets 'em sharp!

When you sharpen a convex edge all you are hitting is the very edge. It's done at a higher angle then a conventional V-bevel. I use rods and flat diamond sharpeners exclusively for convex edges. Then strop.
Scott

Could someone please explain the procedure for sharpening a convex edge with a stone or flat diamond sharpener?

Thanks,

 

[JD Spydo]

Magnussen uses a belt sander to produce the convex edge and then finishes the edge with stones. His edges are thus far the sharpest I've ever encountered. I seen lots of blades in my days and attended a few shows now. He gets 'em sharp!

Do you by chance know what grit size of belt paper he uses. When I use sandpaper for sharpening or reprofiling I generally don't use any grit larger than 280 or 320. And that's Norton's grit size. I find that all makers of sandpaper and abrasive products seem to have their own system of grading their grit sizes.

Also I have heard that the late Bill Moran was the GODfather of the convex edge. I wonder if anyone here knows what Mr. Moran used to sharpen his edges?

 

[Gossman Knives]

Could someone please explain the procedure for sharpening a convex edge with a stone or flat diamond sharpener?

Thanks,

I actually do it holding the knife in one hand and the sharpener in the other hand. Look at the attached pics. It is difficult to explain in writing. If you can wait about a week and half, I'm doing a demo at my campout/shop tour next weekend that either Tonym or Joezilla will be video taping and will post on the forum.

These are with a rod but the same can be done with a flat sharpener.

Scott

 

[baldtaco-II]

Moran may have made claim but they predate him by a lot.

http://members.cox.net/~yuzuha/jisgrit1.html
http://users.ameritech.net/knives/grits.htm

 

[Gossman Knives]

Forgot to add the method I use works well on zero scandi grind/edges also. I had a dinged up Mora that I sharpened out the nicks using this method.
Scott

 

[Dannyboy Leather]

Post expired.

 

[Gossman Knives]

Dannyboy, I think the whole mousepad idea was because people thought you had to hit the entire blade when sharpening a convex edge. This is true when sharpening on a belt grinder or stropping but not so with a stone, flat or rod sharpener. I've seen some blades messed up real bad from improper sharpening on a belt sander. You can't properly sharpen a convex grind/edge on just any belt sander. You need the right slack belt attachment to properly sharpen. Also, all convex grinds are not done at the same angle. Depends on the makers method.
Scott

 

[cotdt]

Didn't people use a slack leather strop in the past? They can be loaded up with abrasives and produce convex edges.

I agree that convex edges are not some new fad. It's been used since antiquity.

 

[Gossman Knives]

Didn't people use a slack leather strop in the past? They can be loaded up with abrasives and produce convex edges.

I agree that convex edges are not some new fad. It's been used since antiquity.

Barbers used strops the most and they stropped hollow ground straight razors. When a strop is attached to a table or bench and left to hang freely, even pulled tight you will still get the convex profile you need for stropping. I use an old leather belt loaded with jewelers rouge.
Scott