How to Sharpen All Knives
By Tom Larson | Apr 27, 2021
Learn how to sharpen serrated and non-serrated knives, what tools to sharpen them with and the technique used to achieve the finest of edges.
It was on a family outing to attend Archeology Days at the Mitchell Prehistoric Indian Village in Mitchell, South Dakota, that I was first introduced to some of the sharpest of man-made blades. I’ve been fascinated since boyhood by any tool made to cut, so imagine my curiosity as I watched a young fellow practicing the ancient art of flint-knapping, which is a controlled chipping away of bits of stone to sharpen and shape their edges. I also noticed a display of long, slender, shiny glass-like shards, the likes of which I hadn’t seen before.
The Mitchell site’s director, Dr. Adrian Hannus, explained that these blades were actually flakes of obsidian, a naturally occurring type of glass. He added that, when he had needed some surgery, he talked the surgeon into using a replica of these ancient tools instead of their modern metal counterparts. It was a little startling to me that prehistoric tools could be used in place of modern scalpels, but Hannus said he had been told the cutting edges of the ancient knives were just one molecule thick, making them about 100 times sharper than modern scalpels.
The skill of those who crafted the obsidian blades is indeed impressive. So are the sharpening skills of modern barbers, butchers and others who make a living with blades they maintain. Hence, my method for creating sharp blades is, in my mind, only “pretty good” (See How to Talk Farmer, November/December 2007).
The sharpening methods described here are those I have practiced for decades, and the sharpening devices I use are worn and simple. They were inexpensive when they were new. For knives, I use a synthetic bench stone. It has coarse grit on one side for removing nicks and a finer grit on the other for creating a smoother cutting edge. For many purposes, this is the only stone needed, and the results are good, especially if the knife is used with a “sawing” motion.
When dressing fish, fillet knives are typically pushed along the backbone from head to tail without “sawing” back and forth. When used this way, an even smoother edge works best. I use a medium grit Arkansas bench stone or a paddle stone to work toward the finer edge needed by fillet knives.
To create a beautifully polished edge, I use a leather strop loaded with polishing compound after the stones, or just for touch-up. The resulting, razor-like edge isn’t really necessary except for fillet and wood-carving knives, but I routinely put this sort of edge on my pocket knives because … well, maybe just because they are such a pleasure to use.
Follow the directions below and you will never be frustrated by a dull knife again.
1. Obtain a bench stone (6 or 8 inches long and 2 inches wide) that’s coarse on one side and finer on the other, a medium-grit Arkansas stone (a 6- or 8-inch stone would be better than the small, broken one I use) and a strop and compound if you want finer edges.
Strops are available in woodworking catalogs, or you could make one yourself, as I did by gluing leather to a piece of wood. Norton makes both synthetic and natural stones and is an old, commonly available brand. The combination and Arkansas stones are meant to be used with cutting oil made for sharpening, but for kitchen knives I just use water and liquid soap smeared on the surface of the stone.
Image Tom Larson
2. Under good light, inspect the cutting edge of the knife you’re about to sharpen. If you can see the edge as you rotate the knife, it is dull and will benefit from a good sharpening (remember the obsidian knives with cutting edges that are one molecule thick).
3. Next, secure the combination stone so you have both hands free to hold the knife. A woodworking vise works great, but a more convenient method when in the kitchen is one that I saw Sarah Moulton (a Food Network chef) use as she was demonstrating how to sharpen a chef’s knife. She dampened a small cloth and folded it to fit under the sharpening stone. There is enough friction between the cloth, the stone and the countertop to keep the stone in position even when drawing the knife vigorously over the stone. This is simple and much safer than holding the stone with one hand and moving the knife over it with the other.
I speak from experience here. While sharpening a large turkey-carving knife on Thanksgiving Day a few years ago, I held the stone in my left hand and stroked the knife over the stone with my right. When I was nearly done, I pushed the knife a bit too far and pulled it back under the stone and slashed the back side of my finger. Treating the infection that set in a few days later required IV antibiotics administered in the hospital.
4. Move the knife across the stone as if trying to slice it. With the stone perpendicular to the edge of the table and the sharp edge of the knife toward you, put the heel of the knife (the part closest to the handle) in the upper right corner and pull toward yourself and across the stone until the tip of the knife is in the lower right corner. This stroking will create scratches that form mini teeth on the cutting edge, which prove advantageous in cutting some materials.
With long knives or a short stone, you can work the knife over the stone in sections in order to create scratches that are not parallel to the cutting edge.
I work by moving one side of the blade repeatedly over the stone and then making about the same number of strokes on the other side in the opposite direction.
Also, pay attention to the angle of the cutting edge. You create this by changing the distance between the back of the knife and the stone. More distance creates larger angles, which are better for durability and good for cleavers and butcher knives designed for heavy use. Less distance gives a thinner edge, better for fillet knives and knives used for fine slicing and carving wood. To find recommended angles for different types of knives, consult the Norton Web site at NortonStones.com. I prefer to work by eye and feel, so I don’t measure angles. Experiment with different angles on different knives, and try them out by using the knife. You’ll soon develop a sense of the angles you like. To decide when you are finished, check to make sure the edge is no longer visible.
5. If you want a smoother edge than that obtained by using the finer side of a combination bench stone, move on to a medium, or finer, Arkansas stone. The method is no different from that used with the coarser stone. Stroke the knife over the stone as if trying to slice with it. Your earlier work with the previous stone has already made the cutting edge invisible, so test the smoother edge obtained with the finer stone by holding the knife as you did to sharpen it and make a slicing cut on a pile of newspaper. If the knife slices easily through the top layers of paper, you’re done. If the knife snags and tears the paper or if more than slight pressure is required to slice the paper, return to the stone and make a few more strokes, alternating sides of the cutting edge. If the paper still isn’t easily sliced, return first to the fine side of the combination stone and alternate strokes there. Then return again to the Arkansas stone and test again. With practice, all of this becomes second nature, and you will be pleased with how your knife work is improved and made easier because you are using a really sharp knife.
6. Polishing the edge to near-razor sharpness is just as easy as the first steps: just pull the knife over the strop, but this time with the sharp edge trailing so it doesn’t cut the leather. Alternate sides and direction with each stroke, and test with newspaper as described above.
Serrated knives have one side that is about the same as other knives, and the cutting edge can be improved by sharpening that side in the manner I have described. If the blade still cuts poorly, the “toothed” side of the blade needs to be sharpened as well. This side needs different handling to avoid grinding away the “teeth.”
Image Tom Larson
1. Find a round file that fits in the depressions between the teeth by fitting drill bit shanks into the depression. Look for a file that is the closest size to the drill bit that fits best. For most serrated knives, you can find a chainsaw file that will fit – they are available everywhere.
2. Fasten the serrated knife’s handle in a wood vise (or a metal vise padded with wood) and stroke the depression between the teeth (use full strokes and count them) at one end of the blade until you can see that the file has cut to the other edge. Do the same number of strokes and maintain the same angle in each of the remaining depressions. If the blade flexes too much as you move from the handle to the tip, re-clamp it with the completed part of the blade in the vise.
3. When you are done, there will be a ragged edge on the smooth side of the knife (known as a wire edge.) Remove the wire edge with the fine side of the combination stone. This sharpening method creates a dramatic increase in how aggressively a serrated knife cuts. Be careful, and if others use the knife, warn them that the knife will now cut extremely effectively.
Steel made for sharpening
Using a device known as a sharpening steel, it is possible to change the edge of a knife so it will cut some materials more effectively. This can be done after the work with stones described above, or it can be done as a quick way to get more use from a knife that is starting to become dull. Steels are rods that have shallow striations along their length.
Hold the steel in one hand and draw the knife from the steel’s handle to its tip, while pulling the knife across the steel, first on the upper side of the steel and then on the under side. An alternative is to place the tip of the steel on a surface, such as a cutting board, hold it vertically and, starting next to the knife handle, push one edge of the knife downward along one side of the steel while at the same time pulling the knife toward you. Repeat with the other side of the knife on the other side of the steel. Three or four strokes on each side of the knife are all that is required.
I easily shaved a patch of hair from my arm with my pocketknife after completing all of the sharpening steps described above, except the steel. Maybe I should upgrade the title of the article to “A Sharpening Method That’s Not All That Bad,” but give my methods a try and decide for yourself.
An avid gardener and woodworker, Tom Larson combines these passions whenever possible. He keeps his knives and other cutting tools razor sharp at his home in Sioux Falls, South Dakota.
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