It is amazing how often I’ll ask to see a knife, only to realize that it is so dull that a butter knife would outperform it. Upon mentioning this fact, the first question I receive is usually “Can you prove it?” After letting the other party inspect the edge on my EDC knife, they usually agree and then exclaim that their knife is dull because they don’t have a knife sharpener. If you are this person, this article is written for you. I intend to walk you through the knife sharpening basics, and then recommend what I think is the best knife sharpener at a few different price points.
Why Does A Knife Get Dull?
Before we dive into sharpeners specifically, it is important to understand exactly why a knife gets dull. There are several factors at play here. First it is important to understand the edge. The edge is where both sides of the blade meet. Depending on steel type (and associated grain structure for the material scientists), the cutting surface of the edge can be as small as only a few molecules thick. As you use your knife over time, you slowly start to roll this edge over. Because this is happening at the microscopic level, it’s difficult to notice with the naked eye. When you roll your edge, you are effectively making the cutting surface thicker, or in other words, you have to push a wider piece of metal through the material you are cutting which offers more resistance and resultingly requires more pressure to cut.
Second, steel is a wear material. If you drag steel across another material, particularly one that is hard and tough, you will slowly remove molecules from the thinnest point on your edge. This is called galling. This process is accelerated by corrosion. Again, this happens at the microscopic level so it is hard to see with the naked eye. This can easily be felt with a finger though as the knife won’t feel like it is “biting” as you run your finger softly against the blade. Note: I do not recommend running your finger across your blade for safety reasons unless you are experienced in this practice. Much like rolling your edge, material wear will slowly make the cutting surface of your blade thicker which will make your knife cut worse.
Knife Sharpening Basics
Now that you know why an edge gets dull, let’s talk about some of the basic principles when it comes to sharpening. When sharpening a knife, you are simply using a coarse material such as a sharpening hone to remove steel from each side of your edge to narrow the cutting surface again. This process is very much like sanding a piece of wood. You are really just rejoining the two surfaces on each side of the edge.
Sharpening angles are extremely important as they greatly affect how long your blade will hold its edge as well as what cutting properties it will possess. Most knives are sharpened to an angle of 15 to 25 degrees per side (or in other words a 30 to 50 degree angle total). Typically, the smaller the angle, the sharper the knife will be but at the cost of edge retention. On the contrary, a larger angle will hold the edge longer but won’t cut quite as effortlessly. Typically, an edge angle is tailored to the knife style and knife steel. To give you an idea of what kinds of blades like certain edges, here is a quick list:
15 degrees (30 degrees total angle)
This is an extremely fine edge that is most suited for disposable blades. Razors, box cutters, surgical tools such as scalpels, and other similar tools. This edge will not last long at all, but will be laser sharp. This is too fine for most pocket knives and only few high end and exotic steels can hold a usable edge for long at this angle.
20 degrees (40 degrees total angle)
This is probably the most common and most useful all around angle, and probably what you will want to sharpen your knives to. This is ideal for pocket knives, camping knives, kitchen knives, and many other types. This offers a nice balance between edge retention and overall sharpness. This angle can still shave hair off your arm with ease so for most general purpose cutting, there is no need to go smaller.
25 degrees (50 degrees total angle)
This is best suited for edge retention, and is ideal for knives that you don’t want to have to sharpen often and are willing to live with only a moderately sharp blade. This is also ideal for knives that will see some serious abuse, such as hunting knives and camping knives. If you are the kind of person who likes to baton through wood or chop with your knives, this is an ideal sharpening angle for you.
The actual technique used varies to some degree depending on the setup, but in each case you are simply removing material from your blade to narrow the cutting surface. This usually consists of running your blade repeatedly across a whetstone or diamond stone. Typically you will start with a coarse grit (as far as stones go, although they are all very fine) and work your way down through two or three grits before your knife will be sharp. In some cases, if you have an electric knife sharpener, you may be using a belt or wheel instead of a stone. The concept is still the same in this case.
For a more in depth guide on these techniques, you can go here to read more about knife sharpening basics.
Knife Sharpener Reviews
Spyderco Triangle Sharpmaker
The Spyderco Triangle Sharpmaker is a superb sharpener that is extremely easy to use. Included in the kit is a plastic base, two medium stones, two fine stones, and a pair of finger guards. The kit also includes a detailed instructional sharpening video to teach you the ins and outs of knife sharpening. You have the option of choosing a 30 degree or 40 degree total angle, so it should cover most of your tools and certainly all of your knives whether they are kitchen knives or pocket knives (both plain edge and serrated). You may also lay the stones horizontally and use them like a regular whetstone.
To use it, simply start with the coarse grit stone and set them up in the spot designated for your chosen sharpening angle. Start with the pointy side of the triangle, as it will remove material the most quickly. You slide the knife down the stone for about 20 passes per side. Then switch to the flat side of the coarse grit stones and do 20 more passes. Repeat the process with the fine ceramic stones and you are done! It doesn’t require a lot of hand pressure on your blade, so be gentle. It usually takes about 5 minutes to put an extremely nice edge on my knives when I use this sharpener. I highly recommend watching the video before you start, as it will save you time and leave you with a nicer edge when you are done.
It should also be noted that the versatile nature of this sharpener makes it easy to sharpen other items as well. It easily doubles as an axe sharpener, as a fish hook sharpener, and can easily sharpen darts, punches, scribes, or a number of other tools. You can also get replacement stones for it, which makes life easy if you sharpen a lot of knives.
Worksharp Knife and Tool Sharpener
The Worksharp Knife and Tool Sharpener is pretty heavy duty and particularly ideal if you have a lot of knives and tools that need frequent sharpening. This sharpener is powered and drives belts in a variety of grits. There is an attached blade guide that allows you to maintain your sharpening angles.
The Worksharp is flexible and allows you to sharpen at 40 degrees, 50 degrees and 65 degrees (for scissors) total angle. The abrasive belts come in 80 grit, 220 grit, and 6000 grit. Like the Sharpmaker, the Worksharp comes with an instructional DVD and comprehensive user guide. To use it, you simply fire it up and pull your knife through the guide, running along the length of the edge of your blade. It takes only a couple of passes on each side of your knife on each grit. You can sharpen your knife in roughly two minutes with this setup, with most of the time going towards changing the belts. However, it should be noted that if you have a lot of blades to sharpen, this machine can save you considerable time as you can run all the knives at one grit and subsequently drop down to the next.
The Worksharp is a great kitchen knife sharpener (I recommend 40 degrees) and a great pocket knife sharpener (again, I recommend 40 degrees), but it also makes sharpening other tools a breeze as well. You can easily sharpen your mower blades, shovels, scissors, hatchets, etc. At the end of the day, this sharpener puts an excellent edge on anything you can throw at it so if you need frequent sharpening, it’s a great way to go.
Pretty Much Any Whetstone
Yes, that’s right. A whetstone, often called a bench stone, a water stone, or a sharpening stone is an abrasive block (most aren’t actually natural stone) that can either be hand held or placed on a table. You simply run the blade of your knife along the stone, alternating sides. A whetstone can be a little bit more difficult to use than the above two sharpeners, mainly because there is no index or reference by which to set your angle. This is done by feel and you more or less have to eyeball it.
That said, whetstones have been used to sharpen knives and tools for many years, long before any of the above tools were ever invented. With some practice and care, you can become a very skillful sharpener on a whetstone. Because of the infinite amount of angles you can set, you can put an edge on anything from a razor blade to a kitchen knife to a chisel. Two advantages to whetstones are that they are extremely portable (assuming you get a small one) and they are extremely cheap compared to some of the more highly engineered sharpeners out there. Interestingly, many people can actually put a better edge on a knife using a whetstone versus anything else. If you don’t have one, it’s definitely a nice tool to have, especially on long trips where your knife may get dull before you have access to a sharpener.
No knife sharpening guide would be complete without mention of stropping. Stropping is a finishing technique used to polish the edge of a blade after it has been sharpened. Contrary to intuition and unlike the sharpeners above, a strop doesn’t actually remove any material. A strop simply realigns any microscopic indentations in your blade. Stropping is most common for things like straight razors, but for someone who wants a perfect edge on their knife, a strop is the way to go.
A strop is typically leather, and can either be hanging or fixed to a hand held paddle. To use, you simply slide your blade gently up and down, alternating sides. This is an extremely gentle process, and many people who use strops do so before each cutting operation (for instance a barber usually strops a straight razor before performing a shave on somebody). Most people use a little bit of strop dressing or buffing compound in addition to aid in the process. Stop dressing serves two purposes; the first is to preserve the leather on the strop itself and keep it supple while the second is to slightly increase the drag on the blade to improve the stropping process.
A strop is a great way to get a laser sharp edge, but be prepared to repeat the process often as the edge gets bit fragile with a strop. It should be noted that stropping isn’t really ideal for your survival knife. It’s moreso ideal for knifes that do more delicate work.
So there you have it. Hopefully this guide points you in the right direction when it comes to your search for the best knife sharpener to suit your needs. In the end, it is up to you to decide exactly what works best for you. If you have any knife sharpener recommendations of your own, or would like to leave a review for one, feel free to do so in the comments! Also don’t hesitate to ask any questions. Stay sharp and thanks for reading!