Many people get confused by what angle they should maintain while sharpening. Much of this is due to bloggers who want to sound as if they have found all the answers. Like if you sharpen this, you have to
use a 23-degree angle, or if you sharpen that, you must sharpen at an 18-degree angle.
Can’t you just see someone trying to keep a 19-degree angle, or for that matter any other exact angle,
by hand? Now that would really be a steady hand. But seriously at what angle should I sharpen as a beginner and still get satisfactory keenness?
In most cases, an angle below 25% will serve you well. However, you don’t want to go too low gaining on sharpness as this compromises the strength of the edge.
In this article, we go into detail on the correct angle to sharpen a knife as well as some key fundamentals of sharpening.
If you are a complete beginner and would like to start with the basics check out The fundamentals of sharpening a knife. Without further ado let’s talk sharpening angles.
At what angle should i sharpen?
Actually, the rule of thumb is to keep your blade under a 25-degree angle to your hone. Generally, the less the angle, the better your edge will be. If you have a protractor, use it to see what this angle looks like. But as mentioned above to low an angle and we cant maintain that sharp age for long.
If you don’t, just take a piece of paper with square edges—which are 90°— and fold it in half at the corner. You now have 45°. Fold the 45-degree angle in half and you have 22.5°. Now don’t get all shook up by that exact-sounding figure, because we are just looking for something under 25° and we want you to know what it looks like.
Setting the primary edge
Remember, we want this to be our final, or primary, edge, as shown in image 1 above. It is important that we thoroughly understand an edge face. The edge face is the flat surface that has been made by grinding on the abrasive.
If your grinding was done by using some type of guide for control, it will appear flat and uniform, as shown in image 1. If the grinding was done free-handed, the edge face will appear to be more rounded and will be a little more difficult to distinguish.
However, the results are basically the same. Remember that this is a magnified view of a cross-section of an edge, so what’s pictured here is an edge the width of which, including both primary and secondary edge faces, could be 1/16 of an inch, or even less.
The primary edge face angle (image 1) is CAB, made up of edge faces AC and AB. This edge face could be so small as to require good light to look at it, depending on how you designed your secondary edge faces. The two edge faces, AC and AB, form edge face angle CAB, and this is the actual cutting edge, which was made on the fine abrasive.
What is double-edging?
The secondary edge face, CD and BE, was made on the coarse hone. This is actually our relief for the primary edge face, and if you look at it under magnification you will notice the coarse “furrows” left by the grit of the coarse abrasive. When two edge faces are used in sharpening, you have what is called “double-edging,” which is a foolproof method of sharpening. Now let’s go a little further and study this all-important double-edging to see how it works.
Let’s take a look at image 2 above. The original, and very dull, rounded edge is indicated by line X. We are first going to grind in a secondary edge face CD with our coarse hone. Achieving this, we turn the blade over and grind in secondary edge face AB, thus giving us edge angle AWC.
The edge will now have a burr (explained in more detail later) on it and will be very rough, which is certainly never satisfactory for any cutting purpose. So far, we have used only the coarse abrasive to remove excess metal, which leaves the edge face with very rough furrow marks.
First and most foremost what is the burr? The burr is your friend. A burr, or wire edge, is a rough, almost microscopic, raised lip of metal that forms when one edge meets the other. It is the only way to be absolutely certain that you have fully ground an edge.
Essentially you grind one side until it meets the other and pushes up a small curl of metal. If you stop sharpening before the burr is formed, your knife will not be as sharp as it could be
Setting the primary cutting edge
We now have our secondary edge, so our next step is to grind in the primary cutting edge. To do this, we go to our fine abrasive and increase the grinding angle just slightly.
To get a better idea of what this double-edging looks like, let’s go to image 3. When we first started grinding the original edge shown in image 2, our grinding was done on the coarse abrasive at angle D shown in image 3 above.
Now, to get our primary edge face, we must increase the angle very slightly—just a few degrees, but enough to give the second edge face clearance. Now we go to our fine hone, and why? Because the fine hone does not have the ability to remove much metal.
If we were to continue on the fine hone at the same angle we used to get the second edge face, we could grow old before we got a good edge. However, when we increase the angle on the fine hone, giving the secondary edge face proper clearance, the primary edge will be set very quickly.
As you can see in image 3, we used angle D on the coarse abrasive, then increased to angle C on the fine hone. This gives us a cutting angle GFH (image 2), and if it’s less than 25°, we will have a super edge.
Wrapping up: Consistency
At what angle should I sharpen? In a nutshell what’s important? Consistency!
You must be able to maintain a consistent angle while you are sharpening. This can be tough to do, which is why there are so many gimmicks and sharpening systems on the market.
They don’t provide any magic. All they do is help you keep your edge at the same angle throughout the sharpening session.
Maintaining consistency is a primary reason freehand sharpening with bench stones or Waterstones is a little tricky. It takes a lot of experience and practice to keep the edge at a constant angle stroke after stroke using only your hands and eyes.
Finally, there is just plain cruelty and misuse. While I’m certain none of you would ever use the sharpener on the back of an electric can opener or store your knives loosely with other tools in a drawer, it does happen. And when you add soft steel and thick angles to the general abuse that knives see while whittling, you end up with tools that are more adapted for bludgeoning oxen than fine slicing basswood.