ABOUT SHARPNESS
BLADE MATERIAL
Blades are available in ceramic, carbon steel, high carbon steel, stainless steel, high carbon stainless steel as well as specialty steel alloys.
Each material has properties that affect strength, flexibility, rust resistance and sharpness. In general, the harder the material, the stronger the edge will be and the longer the edge will remain sharp. The down side of hard blades is that they are more difficult to sharpen
BLADE THICKNESS
Manufacturers decide what the blade thickness should be based on the
intended use. The thickness of the blade has the biggest affect on slicing.
The thinner the blade, the more flexible it will be and the thinner and more
precise the cut can be made
The edge of the knife, the ground edge that runs the length of the
blade, is usually between ¼ to ½ inch wide. The thicker the edge,
the stronger it will be but the less sharp it will feel. The
thickness of the cutting edge has the greatest affect on initial
sharpness and edge life. Thinner edges are sharper and more fragile
CUTTING EDGE TYPES
The edge can take on many forms and be sharpened
to almost any angle and smoothness. There are 2 types of edges that
are of importance, flat and serrated.
The Flat edge
The flat edge, which is also called a fine or smooth edge, is the most common. Both sides of the knife are ground to meet at the bottom forming a flat or fine edge. This type of edge can be created with convex, hollow grind, V-edge, double edge and single edge profiles.
The Serrated Edge
Serrated blades have a saw-like blade. Some knives have the same
serrated pattern across the entire length while others have a
mixture of small and large serrations. Serrated blades tend to stay
sharper longer than flat edge knives.
Custom serrated edges are variations of serrated knives and are
offered by some manufacturers. When these knives need sharpening,
they must be sent back to the manufacturer. Two examples of custom
edge knives are Cutco’s, Double-D edge and Henkel’s Eversharp Pro
series
EDGE PROFILE
The shape of the knife edge (profile) effects how much force is needed to cut as well as how long the edge will last. The correct profile will allow the maximum sharpness to be obtained while still maintaining strength and achieving good edge life.
V-Edge or double
V-Edge or Double Bevel: This profile can produce one of the
sharpest edges, especially if the blade is thin and a very small
angle is used. It is the most common edge that manufacturers
put on blades.
Convex: This is a multi step process that can only be done with specialized sharpening tools. The convex edge starts at a slightly higher point on the knife to create a gentle curve. This is a very effective way to create a sharp edge on thick blades where the strength needs to be maintained.
EDGE ANGLE
The angle that is put on the edge has the greatest affect on initial sharpness and edge life. The smaller the angle, the sharper and more fragile the edge. The 15 and 25 degree angles that can be seen on the drawing create a fine edge, yet the 15 degree angle produces a sharper and more fragile edge compared to the 25 degree angle.
Typical Angles and Profiles
Click this Link to see my suggested profiles and angles for various knives