If you’re serious about knives, you’re probably also serious about sharpening (or at least you should be). The only way to truly appreciate the full potential of a knife is to ensure that is has the best edge possible. “Best,” however, is a relative term.
 
There are many factors that determine the type of edge a particular knife is capable of taking and how long it will be able to retain that edge in use. These include the alloy composition of the blade steel, the steel’s manufacturing method, the blade’s heat treatment, its grind and thickness, and the shape and geometry of the actual cutting edge. Of these factors, the only one most people can really control is the latter one, so let’s examine not only how to get the most out of your edge geometry, but how to do it quickly and easily with Spyderco’s Tri-Angle Sharpmaker.
 
Few cultures understand the nuances of knife sharpening better than the Japanese. Their preparation of raw foods like sushi and sashimi is literally defined by the ability to precisely cut delicate pieces of fish without tearing the fibers of the flesh. This extreme attention to detail has led to the development of a myriad of specialized kitchen knife patterns, each optimized for a particular task. It has also inspired an equally meticulous approach to knife sharpening that is unequaled in other cultures. Even the basic elements of that approach can teach us a lot about what it truly takes to make a knife sharp.
 
Most cutting edges begin with the blade’s primary bevels—the surfaces that taper from the full thickness of the blade down to the edge. These bevels may be flat, concave, or convex based on the specific “grind” of the blade (i.e. saber, full-flat, hollow, etc.). In Japanese, they are known as kire-ha, or the “blade road.” For ease of reference, let’s assume that we’re sharpening a saber-ground blade—one with a flat bevel on each side that extends only partway up to the spine. The flat bevels of this blade are its kire-ha. If they tapered uniformly to meet at the cutting edge, they would define an acute “V” shape and create what is known as a “zero-ground” edge. Although this edge may be extremely sharp and strong, maintaining it in that form is difficult because each time you sharpen it you must remove steel from the entire surface of each bevel. This style of sharpening is known in Japanese as beta-togi.
 
The disadvantage of this method of sharpening is that it requires steel to be uniformly removed from the entire surface of the kire-ha­—a slow and laborious process. To make sharpening this style of knife quicker and easier, a “micro-bevel” or itoba is often added. This is done by lightly sharpening at a more obtuse angle so only the very edge of the blade is affected. The process of adding an itoba is called itohiki.
 
On most knives, the primary bevels taper to leave a thin area of steel near the edge, but do not actually meet. Instead, a second set of bevels is ground at a more obtuse angle to create the “V” of the actual cutting edge. Known as koba or danba in Japanese, the included angle of these “edge bevels” must be appropriate to the type of steel, its hardness, and the knife’s intended use. While an acute angle—like 30-degrees—will cut extremely well, its narrow structure may be weak and prone to chipping or rolling.
 
To avoid weakness at the apex of the “V,” the Japanese typically add an itoba micro-bevel to this style of blade as well. By sharpening the distal portion of the cutting edge at a slightly more obtuse angle than the koba, they create a stronger structure without removing a significant amount of steel. The result is a terminal cutting edge that is both strong and exceedingly sharp, backed by a more acutely angled bevel that reduces friction and transitions smoothly into the blade’s primary bevels. Known as a “compound bevel,” this style of sharpening approximates the extreme cutting performance of a hamaguriba (convex or “appleseed”) edge that many sharpening enthusiasts consider to be the ultimate synthesis of cutting performance and strength. 
Creating a compound bevel with traditional Japanese waterstones requires a tremendous amount of skill and control that only comes with years of practice. Fortunately, Spyderco’s Tri-Angle Sharpmaker provides a powerful, easy-to-use shortcut to achieving this perfect cutting edge. The Sharpmaker’s base includes two sets of holes for its triangular ceramic rods. One set (marked “Edge”) holds the rods at a 40-degree included angle, and the second set (marked “Back Bevel”) holds them at a 30-degree included angle. While most people consider these angles to be an “either-or” choice, if your goal is to create a compound bevel, the answer is actually “both.” 
Let’s say you have a kitchen knife with a relatively thin blade. When you sharpen it with the Sharpmaker’s rods at a 30-degree included angle, you get a very keen edge that cuts beautifully, but dulls somewhat quickly. To improve its edge-holding ability without sacrificing cutting performance, sharpen the edge again with the rods set at the 40-degree included angle. Use a light touch and just a few strokes to create a slightly more obtuse micro-bevel that is more resilient and will stay sharper longer.
 
Similarly, you may have a stout everyday-carry knife that works very well with a 40-degree edge angle. After repeated sharpenings, however, enough steel has been removed from the edge to move it up into a thicker area of the primary blade bevels. That thickness creates drag that hampers the blade’s cutting performance. No problem. Take the already sharp 40-degree edge and sharpen it again with the rods in the 30-degree “back bevel” position. Although the abrasive rods will not actually touch the apex of the “V,” they will remove steel at the top or “shoulders” of the “V.” This thins the cross-sectional profile of the edge, creates a compound bevel, and reduces drag when the blade passes through the materials it cuts.
 
The compound-bevel method of sharpening is a centuries-old method of wringing maximum cutting performance out of cutting tools. And with Spyderco’s Sharpmaker and the knowledge you’ve gained from this article, that extreme sharpness has never been easier to achieve.

OUTDOOR RETAILER

At the end of July (after the release of our last byte newsletter), Spyderco was proud to exhibit at the Outdoor Retailer Summer Market at its new home in Denver’s Colorado Convention Center. The largest U.S. trade show for the outdoor sports industry, the four-day event attracted more than 30,000 attendees and 1,400 exhibiting brands. It was also the largest trade show ever held at the Convention Center.

Thanks to all those who visited us at the show for your continued interest in Spyderco products!

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