Edge Guys... Edge....

Section Three: Edge Basics

Most kitchen knives are flat ground, meaning that the blade tapers directly from the spine to the edge. Hollow ground, convex ground and saber ground blades are rarely found in the kitchen. I mention them only to confuse you.

Edges come in a variety of flavors. The most common are the V-edge, double beveled edge, chisel ground edge and the convex edge.

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V-edges and double beveled edges are variations on a theme. The edge found on your kitchen knives is most likely a V-edge, meaning, oddly enough, that the edge bevels form a V, two surfaces intersecting at a line of (ideally) zero width.

A double bevel takes this idea a little further by adding a second, more acute, angle behind the edge bevel. This secondary bevel is sometimes called a back bevel or relief angle. It’s purpose is to thin the metal behind the edge. The thinner the edge, the greater the cutting ability. However, an edge that is too thin is susceptible to damage. So you add a smaller, more obtuse primary bevel to the very edge to give it the strength to avoid damage from impaction, chipping or rolling.

Chisel ground edges are primarily found on Japanese knives, especially sushi knives. The edge is ground only on one side. The other is side is flat. Hence they come in right and left handed versions. Chisel ground edges can be extremely thin and sharp. If the edge bevel is ground at 25 degrees and the other side is 0 degrees, you have an included angle of 25 degrees – considerably more acute than the average Western knife.

Sometimes known as hamaguri-ba, the convex edge arcs in a rounded curve down to the edge. Thus the final edge is the intersection of two arcs, creating a very sharp edge with more metal behind it than the standard V-edge. Convex edges are generally formed on a slack belt grinder, so they are difficult for the home sharpener to achieve. This can be remedied with the mousepad trick found later in the tutorial. See the Convex Grind FAQ for sharpening methods and a comparison of the convex edge with other edge types.

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A double bevel. The wide area is a 10 degree back bevel; the narrow section is the 15 degree primary edge face.

The back bevel also solves one of the great problems with V-edges, the fact that the metal behind the edge gets progressively thicker as the knife is sharpened over time. The knife doesn’t cut as well and becomes harder and harder to sharpen. The answer is to grind the shoulders off the edge at an acute angle, i.e. add a back bevel, then reestablish the primary bevel.

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If you sharpen your knife without grinding a relief angle, your edge will thicken over time.

Micro-serrations: True or False?

Knife geeks frequently talk about “micro-serrations,” microscopic teeth on the edge of the knife. Is this really true? In a word, yes. Sharpening by its very nature creates a scratch pattern on the edge of the knife. The coarser the stone, the coarser and deeper the scratch pattern will be and the larger the micro-serrations. Conversely, the finer the stone, the finer and more polished the edge will be with less prominent micro-serrations. The real question is, which one is better?

This is one of the great debates in the knife world – the razor sharp polished edge versus a toothier edge.

John Juranitch in his book “The Razor Edge Book of Sharpening” is emphatic that a polished edge is the answer, that micro-serrations are indicative of a dull knife. His experience comes from sharpening knives for the meat processing industry. Meat cutters go through knives faster than tissues in flu season, so Juranitch’s conclusions are hard to dispute.

However, Joe Talmadge, author of the Bladeforums “Sharpening FAQ;” Cliff Stamp, physicist and knife nut; Leonard Lee, president of Lee Valley Tools and author of “The Complete Guide to Sharpening;” and many others have come to the opposite conclusion: that micro-serrations, in the right context, can be a very good thing.

What is the right context? Later on we’ll examine the difference between push cutting and slicing, their applications in the kitchen and the value of various levels of polish on your knife edges. Which leads us directly to:

The Meaning of Sharpness