Creating a convex edge using a guided sharpening system like the Wicked Edge is not too difficult with some practice. Basically it involves sharpening the blade at different angles, creating a multi-beveled edge. These edges are then blended together by means of stropping.
You can find more information on this on the internet:
- The Wicked Edge FAQ;
- YouTube videos on the Wicked Edge, particularly this one (featuring my favourite folder, a Chris Reeve Sebenza) and this one;
- A thread on convex edges at the Wicked Edge Forum;
- Clay Allison’s blog summarizes a lot of what I have learned creating this blog post. I just had to experience it myself. Clay has much better pictures than I have.
Method 1: from most acute angle to least acute
The first method I applied was the method with which you set the most acute bevel first, then the next less acute one, then … until you arrive at the least acute bevel (with the highest angle).
In theory this is the easiest method, because at every angle you create a full edge. This should be easy, because you should feel a burr when you have completed the edge. Once you feel the burr, you go on to the next less acute angle
Practice showed something different, mainly because it is extremely difficult (impossible for me) to feel a burr once you have completed an edge when you set this edge on top of another one with a difference of only one or a few degrees. Also, it is a very time-consuming method, since you have to recreate every edge using (as it appeared) low-grit stones and then use the whole progression again up to the 1600 stones.
The knife I practised on was a Global Santoku knife, made of a steel with a Rockwell hardness of about 57 HRC. I wanted to create bevels of 16, 18, 20 and 22 degrees. Starting at the lowest angle, I did so in that order.
First I created an edge at 16 degrees. To do so I went through the full range of stock WEPS stones: 100, 200, 400, 600, 800, 1000, 1200 and 1600 grits. See below for the result. I didn’t bother the top of the edge did not seem polished, since I was going to set other edges on top of it.
Then I tried to create a new edge at 18 degrees on top of the 16 degrees edge. I had read this should go very quickly, so I went for the 1600 grit stones. But no matter how hard and how long I tried, nothing seemed to happen. So I went back to the 1200 grit stones… nothing either. 1000, 800, only at 600 I started to seen something. But even with 200 grit stones the forming of the new edge went quite slow. So I took the 100 grit stones. And then it went fast, almost too fast. After only a few strokes I had set a new edge of 18 degrees on top of the older 16 degrees edge. It covered around 3/4 of the 16 degrees edge, which was about perfect. But only a few stokes more, and I would have wept out the 16 degrees edge.
The two photographs below shows both bevels; it is spread over two photographs, since the entire edge is slightly larger than 1 mm. Note from the scratch patterns that I set the new edge using up and down movements of the stones, whereas I set the old edge using push motions.
I worked my way up all of the stones and below you can see the result after finishing with the 1600 grit stones at an 18 degrees angle. I tilted the camera about 45 degrees in order to capture the entire edge. As you can see, the new edge is nicely set at about 3/4 of the old edge.
Then I tried to create a new 20 degrees edge on top of the 18 degrees edge. Having learned from the previous edge, I did not start with the 100 grit stones, but with the 200 grit ones. But even then I almost managed to wipe out the previous edges… Nevertheless, after having worked up my way until the 1600 grit stones, the new edge came out nicely and at about 1/2 of the original 16 degrees edge (well ok, slightly over it…), as it should. For the new edge I used push strokes again, to make it clearly distinguishable from the previous edge.
It was time for the final bevel at 22 degrees. Having learned from previous experiences, I now started at 400 grit making up and down movements with the stones. This appeared to be the right choice as the photograph below shows: the final bevel nicely covers one 1/4 of the full edge.
I continued polishing the new edge with the remaining stones. Below you can see the result.
Then it was time to turn the multi-beveled edge into a convex edge. I started stropping with 5 micron paste on leather strops at an 18 degrees angle, which I thought would be nice to start with. However, even after about 100 push strokes per side, hardly anything happened. The 18 degrees bevel had somewhat blended into the 20 degrees bevel, but little had happened to the other bevels, as you can see below.
I decided it was time to strop at a 16 degrees and 21 degrees. And after about 100 push strokes per side at each angle, still with the 5 micron paste, I had obtained a nice convex edge.
Just for a more polished look, I stropped the edge also using 3.5 micron past (again, 100 push strokes per side at 16, 18 and 21 degrees) and the result is below. It may look like the edge is actually rougher than after stropping with the 5 micron paste, but that is not the case; I was simply able to focus better with the microscope, so it shows more details.
All of this polishing resulted in a knife with a mirror edge. It wouldn’t easily shave arm hair, though.