Maintaining a convex edge using the Wicked Edge – challenges on the Fallkniven A1

The Fallkniven A1 is a beast of a knife with a blade length of 6.3” (16 cm), a blade thickness of 0.24” (6mm) and a weight of slightly over 11 oz (305 grams). My Wicked Edge was soon to know…

The blade of the A1 is made of laminated VG10 with a hardness of 59 HRC. The entire blade has a convex grind; so it is not just the edge that is convex.

I had used the A1 for splitting wood and had batoned with it. (Yes, I know an axe is much better for that purpose :-) .) The blade had kept up beautifully: just a slight dulling of the edge and one little microchip that was barely visible with the naked eye.

I knew not a lot of sharpening would be required to restore the edge, but first I had to find out the angle of the blade at the edge of the edge.

My goniometer, which normally helps me to identify blade angles quite easily, seemed not very helpful on this beast of a convex knife.

Goniometer results on the A1.

The goniometer shows two patches of light centering at about 9 degrees (left) and 16 degrees (right) and two smaller patches of light centering at about 22 degrees and 31 degrees. I asked people for help, but nobody was able to give a definitive answer.

It is clear from the picture that the knife is not perpendicular to the goniometer slot. If it were, and the knife were completely symmetrical, the patches of light would likely be at about (9+16)/2 = 12.5 degrees and (22+31)/2 = 26.5 degrees.

So I assumed the edge of the edge had an angle of about 26.5 degrees per side, partly because I couldn’t image an angle of 12.5 degrees per side on such a knife, and partly because I had seen patches of light at low angles also on other knives in the goniometer, which were caused by the fact that towards the spine most blade approach a 0 degree angle.

I emailed Fallkniven to ask them what the angle of the blade was at the edge of the edge. The first reply I got from them was “you cannot do a convex edge on a guided sharpening system”. I then explained in more detail what I wanted to do and they responded again with “don’t do this, you will ruin the edge.” This got funny, but after  I had explained them what I intended to do for the third time, they understood me and replied that “they would be lying if they said the edge were 20 or 21 degrees”, because each of their knives was hand sharpened.

So the Sharpie trick would have to give the definitive answer. I just needed to clamp the knife in the Wicked Edge vise.

That took me four attempts. Every time, once I had clamped the blade, it dropped out after some time. The handle came down simply due to the weight of the blade. I tightened the screws even further and finally I manage to clamp the knife securely.

The A1 clamped securely in the WEPS vise.

I then discovered that the left clamp of the vise had moved almost a centimeter…

The left clamp of the vise has moved considerably to accommodate the A1.

But the knife was clamped securely and finally I could measure the angle of the edge of the edge of the A1 using a Sharpie! Starting at 27 degrees, I went down to 26, 25, 24, 23… I was still hitting the edge of the edge. 22, 21, 20, 19… Even less than what Fallkniven did not want to lie about. Finally, in the neighbourhood of 13 degrees, I did not hit the edge anymore. The edge of the edge had an angle of 13.5 degrees! So the goniometer, even though not very precise, was right after all.

So I wanted to start sharpening the knife at 13.5 degrees. This presented some additional challenges. If I tried to sharpen the knife at this acute angle, the stones hit the vise. Luckily, I managed to squeeze out 14.5 degrees, so I decided to settle on that.

Sharpening the A1 at 14.5 degrees.

Now another challenge appeared. I wanted to set the sharpening rod at the left at 14.5 degrees as well. However…

Impossible to sharpen the other side of the blade at the desired angle.

I had forgotten the left clamp of the vise had moved out so much. I could forget sharpening at any angle below 17 degrees on the left side of the blade!

I then decided to do the blade side by side: first the right side of the blade, then clamp the knife the other way around in order to do the other side.

The edge needed just a little touch-up, so I decided to use the 1000 grit stones. These worked very quickly. In hindsight I had better started with the 1200 or 1600 grit stones, or go to the strops immediately.

I followed by a lot of stropping (at least a hundred stropping strokes per side) with 5 micron paste and then 3.5 micron paste on leather strops. I used quite a bit of pressure.

I took out the knife from the vise and reclamped it to sharpen the other side. This time I decided to go to the strops right away. I did even more stropping than on the other side, since I didn’t use the stones on this side.

I unclamped the knife and the result was a blade that could shave arm hair.

A shaving sharp A1.

Finally me and my friends, the WEPS and the A1, went outside to enjoy the view. Yes, we were in Switzerland.

The WEPS and the A1 in Switzerland.

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