Learn To Sharpen
Learn To Sharpen Your Own Knives At Home
With a little practice and some acquired skills, you can learn to sharpen your own knives, and experience the thrill of making a blade shaving sharp!
Professional Quality Knife Sharpening-
Sharpening is nothing more than a precise, repeatable process to bring the edge of your knife to the keenest possible apex, hopefully hair shaving sharp or better. Some people think sharpening a custom knife is an artform, or some sorcery handed down from wizard to apprentice. I believe that my knife sharpening service is a science based skill, learned through trial and error, and can therefore be learned by anyone with the desire to do so. This first article is familiarizing with some common terminology and practices so we can be on the same page while communicating.
Sharpening a blade is bringing the two sides, or "cheeks" of the knife together by grinding or honing away steel evenly from either side to create an "apex". The objective is to finish this apex to the finest, narrowest "edge width" you can. In well sharpened knives, that edge width is at or below one micron. A micron is approximately forty MILLIONTHS of an inch, so while it sounds simple, the process requires a high level of precision!
There are multiple tools and systems available to professionally sharpen a custom knife, but only one WAY to sharpen. That is, the two bevels of the knife must be ground with stones or sandpaper in such a way as to bring them together and create an APEX, with as small an edge width as possible, in a fine straight line, with no burrs. The "grinding" is where multiple tools and styles come into play.
Sharpening By Hand-
The old tried and true method of sharpening, hand sharpening, involves using stones or other abrasives to grind and shape the bevels, in a progression from coarse to fine grit stones. Typically this style is purely by feel and requires many hours of practice to develop the skills and muscle memory to achieve repetitive success. A good tip is to mark the edge of your knife(JUST the edge) with a black magic marker or sharpie. Then gently rub the knife on the stone while adjusting the angle till you erase all the marker with the stone. This will tell you you're on the edge bevel. Additionally, it is hard to know the angle being applied to the blade. Many sharpeners just follow the angle already there, whether it's right or wrong. Being a machinist, I like quantifiable, measurable, REPEATABLE results, and sharpening knives to the angle appropriate for the steel and the job they do. Read on below...
Fixed angle tools-
There are a number of sharpening aids that set the angle between blade and stone and keep it constant during sharpening. They include Edge Pro, Wicked Edge, Hapstone, KME, Lansky, and others. Some use hand power, some are motorized belts and wheels, but all set a fixed angle and hold it more or less steady. I DO NOT care for the powered models, and here's why: It has been proven through edge retention testing that motorized sharpening of knives is detrimental to the edge retention of a knife steel. It is probably due to overheating the edge on a microscopic level that cannot be recognized with the unaided eye.
Here is an in depth article by Dr Larrin Thomas about power grinding edges.
I use a Hapstone fixed angle hand sharpener, because it's mechanically solid, easy to use, and didn't break the bank when I purchased it. I also bought a full set of diamond stones from 80 to 2000 grit, and some finer natural and synthetic stones. The diamond stones remove material including hard carbides much faster that natural or synthetic stones. For my use, speed, accuracy of angle, and final finish are the most important factors. I still freehand sharpen my own pocket knife sometimes, but YOUR knife will get the best edge I can offer. That requires precision, and a fixed angle HAND sharpener is the way to go.
When I finish the edge on a custom knife, I HAND SHARPEN to an angle appropriate for the normal use of the knife. A 12-15 degree per side angle is perfect for a kitchen slicer made of quality steel, but is way too thin for a hard use survival knife. For this reason I like to have the ability to set the angle and hold it steady through the entire process. Once the bevels are set and symmetrical I always hand sharpen a tiny micro bevel at a slightly steeper angle to offer more strength to the edge. For example, if I've set that "primary" bevel at 12 degrees, I'll hand sharpen a 14 or 15 degree micro bevel to finish the edge.
Types of Bevels
There are a number of ways to professionally sharpen, or create the edge on a custom handmade chef knife or Outdoor Knife, and each has advantages and disadvantages. Some are very specialized, while others are quite common. As you can see in the picture of different bevel types, they vary greatly in the way the blade is brought to an "apex", or the actual cutting edge of the blade. I won't discuss all of these, but I think a few of the more common ones deserve mention. Keep in mind that the picture exaggerates the features of each grind, and we are only looking at the last several thousandths of the blade, usually 1/8 inch or less.
This is by far the most common way to produce an apex in most US knives, particularly for custom kitchen cutlery. At lower sharpening angles (12 -15 degrees per side), it can produce an extremely keen edge capable of slicing hard veggies without breaking them. The disadvantage is there is minimal "thickness behind the edge", to support the apex and prevent rolling and chipping. Therefore a strong, tough steel has to be selected by the maker to support these thin, keen edges. At higher angles(18-25 degrees per side), this type of edge can become a capable "hard use" knife. Your custom knife maker can assist you in choosing the steel for your bespoke knife!
Convex edges serve several purposes on blades, and are most often seen and recognized on axes and hatchets as well as hard use bushcraft knives. They function well on these blades by allowing a little more steel behind the edge for better support and strength. Some folks believe this edge helps food release in the kitchen as well, with the convex curve tending to push the food away from the flat of the blade. Maybe an experiment is in order to verify this claim!
Compound (double) Bevel-
This is the grind I modify slightly and use on all kitchen and low impact knives. Essentially I sharpen the knife to shaving sharp at the appropriate angle for the knife's purpose, then raise the angle one or two degrees and hand sharpen with light strokes to create a "micro bevel", honed all the way to 3000 grit. This allows for a little more steel to support the edge, and helps assure the edge is clean and deburred. After a light stropping with .25 micron diamond paste on smooth leather, this is my favorite edge for kitchen use and my EDC. it is exactly the edge I will put on your blades too!
Hollow Ground Bevel- Another highly common grind is the hollow. As can be seen in the image above, the hollow thins the steel dramatically behind the edge, allowing for a keener edge. It can be employed to produce a fine edge on a thick heavy use outdoor knife, or something as fine and precise as a straight razor. Hollow grinds are employed by several "factory" makers so they can use slightly thicker blade material and still have a crisp edge. In my opinion this helps reduce warranty claims for breakage.
Chisel (single) Bevel-
In the West, this grind is mostly seen in woodworking chisels, planer blades, and such. However the Japanese regularly make kitchen cutlery with a chisel grind. It is important to note that such a knife must be made with respect for the "handedness" of the end user. A knife chisel ground for a right handed person will not perform as well for a lefty, and vice versa.
How to Sharpen-
Now I'll tell you how I put the final sharpening on a Handmade Knife or YOUR knife. It involves a combination of wet, slow belt grinding to set the initial angle of the edge or "secondary bevel", and a final hand refinement of the "micro bevel" apex with the Hapstone Hand Sharpener and a series of bonded diamond stones, seen in the picture above.
For the initial setting of the secondary bevel, I use my Reeder Grinder with the knife sharpening attachment. I can set the angle within a half degree easily with this attachment, and the accuracy pays off! I also use a Kool Mist, which delivers a cooling and lubricating fluid and compressed air to the point of contact between the knife and belt to keep the edge from overheating and becoming brittle. Again, this sets the angle of the secondary bevel (edge), and merely roughs out the profile of that, saving time for me and money for you.
Then it's on to the Hapstone for hand finishing where the edge angle can also be controlled very precisely. I use a progression of diamond and natural stones to hand sharpen, refine, and finish the final edge to 3000 grit, remove the inevitable burrs, and polish. So again, running through a progression of diamond stones from coarse (80 grit) to very fine (3000 grit) I refine the edge, raising and removing a burr at each grit. Even at 80 grit the blade is shaving sharp, and each subsequent step only refines and polishes the edge.
From there it's to a denim strop loaded with Flitz chrome polishing compound, for just a few strokes to further refine the edge. The final step is a strip of top grain cowhide glued to a flattened 1x4 board and charged with 1 micron diamond spray. Here the edge gets a few more strokes to assure burr removal. Final inspection under 20x magnification guarantees a keen burr free edge from butt to tip, and testing with the Edge on Up sharpness tester assures a super keen, high quality edge. (Click HERE to see me using the sharpness tester in real life!)
Notes and Tips for Freehand Sharpening--
Sharpening by hand, or freehand sharpening, takes practice. Don't get frustrated if it takes hours or days to learn! Follow these tips for a head start:
1) I suggest again that you use a felt tip pen to color the edge bevel of your knife before you start. This will help you "find" that edge as you begin to hone or sharpen on your stone.
2) Concentrate on holding the angle steady as you stroke the knife across the stone, first one side then the other, in EDGE Leading passes.
Notes and Tips On Stropping-
My strops are glued to 1x4 boards, and I primarily use only two of these.
The first is a denim strop loaded with Flitz chrome polish. This step requires only 3-5 strokes per side to remove the bulk of the burrs left from sharpening (if you deburred with your stones). It also polishes the bevel and apex and creates a micro convex at the apex.
I follow the denim strop with a top grain leather strop(smooth side out), charged with a 1 micron diamond compound consisting of sifted and screened 1 micron diamond chips in a carrier of water or alcohol. designed to remove lighter scratches and burrs. Again, 3-5 strokes per side is all that is needed to remove all trace of burrs and add some final polish to the bevels.
Keith Nix Knives sharpening services are available to individuals and businesses in Asheville, Weaverville, Swannanoa, Black Mountain, Old Fort, Marion, and greater Western NC.
We'll follow up soon with more of the Learn To Sharpen Series!