Techniques for shaping a convex bevel?

Joined
May 11, 2011
Messages
9
Hello.

I'm from Brazil, and new to the forum (just joined today) and this is my first thread.
I'm not sure if this is the correct session to ask this, or if there is already another thread on this subject (probably yes), but after searching and reading a few threads, I could not find what I am looking for.

I am looking for techniques on how to grind and repair convex bevels, or sabre grinds. I mean actual "how to"s, how to hold the blade, what movements to make, grit progressions, etc, but freehand using only bench stones and files (I don't have a belt grinder, and they are hard to get and expensive here in Brazil). Though I read some articles and watched a few videos about this grind, but I actually need to try it out to feel the benefits and disadvantages. I just am having a lot o difficulty to find out really what kind of technique I need to use to shape a bevel convex.

Learning this is fundamental for me, because the knives used in my region are almost all grinded that way, and their use require a strong edge. Let me give you guys an idea of my situation:

I am a begginer at the art of cutlery (just started getting serious for around 6 months). I am currently studying grinding, sharpening, polishing and restoring blades. I have a few custom made rustic knives here, on a style particular of the region that correspounds to southern Brazil, Uruguay and Argentina. Those knives are used by the cowboys, farmers/ranchers as multi-tool knives, for cutting all kinds of material from leather to bone, wood and even butchering cattle. But it is a tradition for the city dwellers to use these knives as barbecue knives (for preparing and serving meat), since the barbecue here is a very cultural moment. They need to be sharp, and very resistant to impacts, chipping and denting. Bellow are a couple of pictures so you can just know how they look like.
gauchas2.htm

P1010630_1200x900.jpg


I can try taking a few pictures of a knife I need to repair and that have a slight convex bevel with lots of dents on it.

I realy need help on this, because I am very eager to practice, pick up some scrap metals and experiment, but I don't know how to even begin to shape an edge like that.

Looking forward to your comments,

Zeppelin17
 
The tinkering and maintenance forum will show you a great deal of info on this subject.

Most of my knives are convex. I use only a leather strop with black and green compound for maintaining an edge. The above link explains the action needed.

But if you are reprofiling the edge or restoring a very dull or damaged edge you will need much more aggressive tools. I guess you could use stones as long as you vary the angle or you'll end up with a bevel edge.
 
Yeah, that's what I am talking about.
Those videos are gold. They helped me to get an idea of how to work the knives I have here.
The biggest chalenge I have is to remove the dents and then reshape the edge. I fear the method of using a soft cushion and sandpaper won't work for that. And it is really hard to get an uniform edge along the length of the blade using my DMT Diasharp. I tried to work on the blade today using similar techniques (moving the blade outwards the edge) and it worked quite well to make the convex shape, though I am quite sure the edge is completely uneven... Maybe it's just practice?
 
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