Knife sharpening is by far the most common and important knife task you will face while caring for your new knife. If done improperly it can ruin even the best blade. Modern knife steel has made this task less frequent but the hardness of these steels also makes the sharpening process much more difficult.
Before we talk about how to sharpen your knife, let’s first cover a few basics about what makes a knife sharp to begin with. The two key factors are blade angle and blade thickness. The blade angle is measured in degrees from the center plane of the blade surface. The smaller the angle, the sharper the knife will be. For example, a very sharp knife used for may have a blade angle of 10 to 20 degrees (on each side of the center plane of the blade.) But, a blade with this angle is also thinner and requires more frequent sharpening. I knife used for chopping may have an edge of 25%. At this angle the blade is less sharp but more durable.
The desired use of the knife, the knife edge geometry, and the material to be cut all play a role in choosing the right sharpening method. It is also important that you read and understand the manufacturer’s warranty. Improper sharpening may ruin the knife and void the warranty.
The most common methods for sharpening a knife are:
- Polishing or stropping – smoothing the finish of the blade, as in a razor
- Steeling or straightening – aligning the existing steel edge – for example, what is commonly done with a kitchen knife
- Sharpening – typically by using a grinding stone or otherwise creating a new knife edge
Modern-day super steels, ceramics and alloys take additional care. Hollow ground, complex grinds, and serrated edges all require individual attention. Your manufacturer will provide specific instructions, and perhaps specifically recommended sharpening tools for each knife you own. As a result, many top-end manufacturers offer free or low cost tune ups that are like spa treatments for your knife. This ensures the process is completed correctly. Can’t afford the spa treatment? Maybe you can’t afford the knife. When in doubt, please contact us for more information.
P.S. It is generally considered manly to own at least one hard use knife that is not such a safe queen that you can’t actually sharpen it yourself. Do yourself a favor, buy at least one, non-serrated, high carbon steel knife so that you can learn how to sharpen and oil the blade yourself. This is especially important for “collectors” to ensure that their man card is not revoked at some point in the process of knife ownership.
Polishing or Stropping
Probably the most common example of stropping a knife is in the use of a straight razor. The razor’s edge is polished an aligned using a stropping leather. One end of the leather is attached to a fixed position, the other end is held tightly by hand until pulled into the leather is taught. The razor is run along the leather spine first at approximately a 60 degree angle. Then the blade is turned over and run back the opposite direction, again spine first. This process is often performed before each use. The razor may be stropped 40-60 times per side in order to fully polish the edge.
Using a Sharpening Steel
Sharpening steels are most commonly seen in the kitchen. First, it is important to remember that a sharpening steel is designed to align the existing steel on your blade, not grind a new edge. If you use a sharpening method such as grinding you may destroy the finely tuned and even scientifically designed edge of your expensive imported knife.
While stropping is performed spine first, steeling is performed blade first. Place the blade of the knife near the hilt against the steel near the tip. Pull the knife down and across the steel at approximately a 20% angle. Repeat this process on the other side of the steel, pulling the knife again at roughly a 20 degree angle. Five to ten times on each side should be enough. It is important to know your knife. Some may work better with a slightly higher or lower angle, while many Japanese knives are sharpened with an angle on only one edge.
Using a Sharpening Stone
Common grinding stones include whet stones and oil stones. Single stones or kits can have three or more grades of fineness from fine to coarse. Make sure you wet or oil the stone. Maintain the proper angle for your application and be prepared to complete 30 to 40 strokes per side, while moving from coarse grind to fine grind stones to regrind you knife. Again, you may deice to take the knife into a professional sharpener at this point, or use one or more modern tools that make the job easier. The temporary hit to you “man card” will be far less costly than the cost of a new knife.
Sharpening Serrated Blades
After you have finished sharpening the serrated edge of your recently purchased bad ass knife, like many of us, you will consider whether or not you ever want to own another serrated edge again.
But, if you like the meticulous and detailed work that comes along with that bad ass blade, then here are a few extra tips just for you. Also, since it is scientifically proven that owners of more than one serrated knife have a lower IQ than the general population, I write more slowly for the rest of this section.
First, check with your manufacture to see if they provide a specific tool designed for the angle and radius of your serration, or perhaps they can recommend a sharpening system that has proven effective. Then use the sharpening tool to draw with the edge of each grove or notch in the serration unto a small burr can be felt on the opposite side. Then repeat this process for each groove in the serration. Once this is done, flip the knife over and use your sharpening stone to carefully remove the burrs from the other side of the knife. This is the trickiest part, remove too little and you will be left with a curved knife edge, remove to much and you have dramatically change the cutting angle of the serrations, likely making them duller. Good luck! If I wrote too fast for you, please feel free to read this last section again.