Angles and Sharpmakers and Lanskys and Edge Pros and curved blades...

W

Wildewinds

Joined
Nov 20, 2006
Messages
600
So, I'm sharpening a new blade I made the handle for (using Cocobolo and Ebony, it's pretty sweet) with my Sharpmaker. I quickly came to two realizations. First of all, the edge needed to be re-profiled. Secondly, the Sharpmakers sucks donkey balls at re-profiling.

I did some research and noticed that a lot of people like angles of 20-25 degrees for their blades. The sharpmaker can do a minimum of 30 degrees. Is 30 degrees good enough if I want a scary sharp cut-through-plastic-bottles-and-paper-cylinders type of blade?

For re-profiling accurately it looks like I need a guided angle system like the Lansky or Edge Pro Apex. In a dark alley, if you squint your eyes, these two systems look similar. Besides the obvious difference in build quality and materials, does the Apex do anything that the Lansky can't do?

Finally, the blade I'm working on has quite a curve on it. While attempting to re-profile with the Sharpmaker (and a whetstone, and a diamond stone) I noticed that the front curved section was getting a much larger edge than the flat section. Here's a photo illustrating what I mean:

70529350.jpg


The red line indicates how the edge is shaping up. Is that really messed up or typical of a blade curved like that? If it is screwed, will one of those sharpening systems do anything to fix it?
 
Do you keep the blade pretty-much horizontal as you approach the tip, or bring the heel of the knife up?
 
It's the stock thickness behind the edge. The blade is thicker nearer the tip, so to keep the edge bevel the same width, the angle changes along the length. Since you are using a system, the angle is held constant and the bevel width changes with the thickness. You'll see the same thing with any system.
 
Wildewinds said:
I did some research and noticed that a lot of people like angles of 20-25 degrees for their blades. The sharpmaker can do a minimum of 30 degrees.
Click to expand...

Angles can be specified per side or included, the Sharpmaker is 15 degrees per side and there are few people who sharpen more acute.

For re-profiling accurately it looks like I need a guided angle system like the Lansky or Edge Pro Apex.
Click to expand...

To adjust the edge angle you only need a benchstone, the guided systems are mainly for cosmetic benefits for that task unless you have really specific intentions like grind some knives at 10 degrees, others at 12, etc. .

Is that really messed up or typical of a blade curved like that?
Click to expand...

At a given angle, the width of the bevel is proportional to its thickness. Since through the tip the edge gets closer to the spine it is on thicker steel and thus the bevel is wider at a given angle. If the blade has a distal taper it will allow a more even angle. That is one of the problems people have with sharpening tips. The manufacture grinds them so they have the same width and they look even but then when you try to sharpen them you are not hitting the tip at all but just the shoulder.

-Cliff
 
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