There's Bevels To This Stuff...

In high-volume professional kitchens, a chef's knife is the direct extension of their hands. While many cooks understand how to run a blade across a steel, few truly grasp the geometry of the edge. In this tutorial, J. Kenji López-Alt addresses the mechanics of knife sharpening, demonstrating that maintaining your knives is a matter of understanding bevels, angles, and consistent physics.

Demystifying Blade Bevel Geometry

The bevel is the angled surface that tapers down to form the cutting edge of the blade. Most Western kitchen knives feature a double bevel, meaning both sides of the blade are ground to symmetrical angles (typically between 15 and 20 degrees). Traditional Japanese knives, however, often feature a single bevel, where only one side is ground, leaving the back of the blade flat.

Understanding which type of blade you are working with determines your approach on the stones. A single-bevel blade offers unmatched precision for tasks like slicing raw fish or shearing vegetables, but it requires a specialized technique to sharpen without ruining the factory geometry. Double-bevel blades are more forgiving but demand equal attention to angle symmetry on both sides during the sharpening process.

The Critical Importance of Angle Consistency

The most common mistake made on the whetstone is failing to maintain a consistent angle. When you rock the blade or change the angle mid-stroke, you round over the apex of the edge, dulling the knife instead of sharpening it.

Kenji emphasizes that finding a repeatable physical guide—such as using your fingers or a small wedge to lock in the distance between the spine of the knife and the stone—is crucial. Rather than rushing the strokes, chefs must focus on steady, deliberate passes, ensuring the entire length of the blade from heel to tip contacts the stone at the exact same angle. Maintaining this consistency ensures that the bevels meet at a clean, sharp point, creating a reliable edge that holds up under intense service conditions.