Convex edge on damascus blade.

Keith Montgomery

Keith Montgomery

Joined
May 9, 2000
Messages
29,205
I have just noticed something about a convex edge on a damascus blade that I really like. The pattern of the damascus goes all the way to the very edge. This is something that I find very appealing. I am sure that many others have noticed this in the past and it is not news to most, but it was a new discovery for me.

On a beveled edge the pattern is only noticeable up to the edge of the bevel and is not easily visible, if visible at all, in the beveled edge. The reason for this is that etchant is corrosive and it desolves the different steels (and nickel, if pure nickel is used) at differnet rates. This leaves many hills and valleys in the blade. When polished the valleys remain dark and the hills become shiny (the pure nickel stays shiny all the time). When you grind away the bevel for the edge, you remove these hills and valleys and there is no longer any dark and light areas that make it easy to see the pattern welds. When a convex edge is used, this doesn't happen.

Ok, so this is not earth shattering news, but it has educated me and made a difference in the type of edge I will want on all my damascus blades in the future. Before it would not have mattered to me; now it will have to be a convex edge.
 
I'm afraid I don't understand: why wouldn't the "hills and valleys" be removed when creating a convex edge? In order to sharpen an edge, metal must be removed, regardless of whether its a regular bevel or a convex one. Are you sure that the blade wasn't re-etched after it was sharpened?
 
With a convex edge the primary grind basically extends from the very edge of the blade all the way to the spine. This is like the straight side of a chisel ground blade, but with a little curvature leading to the edge (I know that this is more the case with a full convex grind than with only a convex edge, but the example is still fundamentally correct, I think). The pattern wouls show all the way to the very edge on the flat side of a chisel ground blade.

Being that the chemicals that are used to etch are very corrosive, I don't think etching a blade after the final edge was put on would be a good idea. Could be wrong though. Any input from makers on this point would be greatly appreciated.
 
I have never etched a damascus blade after I have put the final edge on it but I have etched blades of 1084 and O-1 after putting the final edge on and it definately dulls them. I had to go back and re do the edge after the etch.
Kyle Fuglesten
 
Originally posted by Keith Montgomery
I have just noticed something about a convex edge on a damascus blade that I really like. The pattern of the damascus goes all the way to the very edge. This is something that I find very appealing. I am sure that many others have noticed this in the past and it is not news to most, but it was a new discovery for me.
Click to expand...

I have a little axe-head pendant made of Devin Thomas raindrop damascus. Terry Kranning put a convex edge on it so the body of the axe clearly shows the raindrop pattern while the edge is just a seried of contour lines running to the end. As you would expect with DT damascus, the pattern is very vibrant. I can't post pics here, but if anyone wants to see it, let me know and I'll send a pic via e-mail. If one of you has picture posting privileges and wants to attach it to this thread as an example, that would be great.
 
Do you mean that the surface pattern differs from the pattern formed on the ground section of the blade (regardless of the type of grind)? If yes, often the ground section has a very attractive pattern. Just curious.
 
Keith, I;ve been thinking about it. I suppose what you mean is that many damascus blades are flat ground. Then for strength, the edge region is convexed towards the edge. The convexity is not all edge, of course. Only the very tip is sharpened (naturally). But because convex edges are by nature "zero-edges," only the very edge itself will be ground or cut away when sharpened. Therefore the etched pattern will go all the way to that sharpened bit.

Also, because the grind changes at the step where the blade is convexed, the pattern can also change a bit - makes it more interesting. I think it can also be seen in very thinly ground flat-grind blades where the final edge bevel is really tiny. Theres hardly any visible edge at all - just lots of the flat bevel (which can be etched).

ON the other hand, there are some makers who never intend their damascus blades to be used and don't actually sharpen their blades at all. So the etch is done AFTER the edge region is formed. IN these cases the entire edge looks like the pattern extends 100% the way onto the edge itself. I suspect the edge may be etched away as well and may not be as good as a refinished edge for cutting.

Just a few thoughts, please correct me if I'm wrong about this. Cheers. Jason.
 
Keith>



Here is a blade that is etched all the way to the edge. There will be a fine bright line at the extreme cutting edge when touched up on the stone.
 
Here's another example:

damascus_3.jpg


This is fully sharpened, both the edge and the clip. Here's a closer shot at Knifeart.com:

http://store4.yimg.com/I/knifeart_1752_190599384

The reason you don't see any sharpening lines is because the clip ground to zero, and the very idea of convexed edges is that you are taking it right down to a sharp edge while convexing. There are no flat planes converging to an edge.

It's also the reason that convex edges used to get a bad rap about being difficult to sharpen. If you've spent your life sharpening flat edge bevels at 15 - 20 degrees, then you would have a slight learning curve on the convexed edges. On these you hold the blade at about 29 - 30 degrees to the stone and make a couple of light passes on each side at the very edge, then strop.

The clip and the edge were fully sharpened right after the tempering so that the knife could be tested. Only after the knife has passed the tests will final finish be put on, etching, etc. done, and finally the guard and handle attached. Once the knife is ready to ship, the edge is just touched up in the manner mentioned above.

Maybe I can post some pics later of the process. That is, convexing the edge after tempering, testing, and so on.
 
Terry -- a picture is worth thousands of words :D That's just beautiful !!
Keith -- I first noticed what you've discovered on my small Peter Martin. There is a very narrow silvery "halo" band at the very edge of the damascus pattern, which is the sharpened edge. Otherwise the pattern extends all the way throughout the blade.
MtMike
 
Terry,

That's a terrific explanation (clear and concise - even I could understand it ;) ) and a very beautiful knife.

Like Keith, I tend to prefer a convex edge - particulalry on a damascus blade. It's not an absolute requirement, but I do find the absence a visible, angled edge aesthetically pleasing.

A follow-up question that I'm sure has been asked before: is there a functional benefit to the convex edge? Does this type of egdge geometry perform better in certain applications?

Here is another example for the thread: damascus Sendero by Fisk:

orig.jpg


Cheers,

Roger
 
Those are some fantastic patterns.

Pete, is that pattern called Magma? It is outstanding! I would love to see a complete blade made from that pattern welded steel.

Terry, I love highly polished damascus. In particular when it looks that good.

Roger, do you know what Jerry calls that paatern?
 
Hi Keith,

This is Jerry's wolf's tooth pattern. You should see it on a 10" bowie. Stunning.

Roger
 
Wow. Thanks for sharing, guys. Beautiful blades.
As a big fan of Bowies, damascus, and convex edges, it looks like I've got to make some phone calls. :)
 
Originally posted by RogerP
Hi Keith,

This is Jerry's wolf's tooth pattern. You should see it on a 10" bowie. Stunning.

Roger
Click to expand...

Thanks Roger, I have a Bowie coming from Jerry in about a year. I just might have to go the extra mile and have him use this steel for the blade.

Just thought folks would like to see Pete's knife that has that great pattern welded blade.

attachment.php
 
Just to let folks know, in Pete's email to me he mentioned that he had changed these bolsters as he was not happy with the etch.
 
I know that pictures can't tell the whole story, but if those bolsters weren't the perfect fit for that blade, I've GOT to see what does :) Too many times I see damascus bolsters with damascus blades, and the patterns just don't seem to go together - in fact it's more common than seeing well matched patterns. Please, please, let's see the knife when it's finished
Mike
 
You must log in or register to reply here.
Back
Top