What Is The Blade On A Knife For? | Jonas Blade

What Is The Blade On A Knife For?

At a minimum, a knife has two parts: a blade that cuts, and a handle to hold. A handle is simple and straightforward, just something you can hold onto with some degree of security and comfort. Back in the Stone Age, the earliest cutting tools were just chipped stone, the blade and handle were only a  single piece. As simple as a knife is, there is also a surprising amount of complexity to be found. 

With that in mind, let’s take a look at the following sections:

How Does The Blade Actually Work?

What Does The Blade Accomplish?

What Else Is There To A Blade?

How Does The Blade Actually Work

Imagine yourself holding a wooden match between your thumb and index finger. If you squeeze that match between your fingertips, nothing much will happen. Now picture a sewing needle instead and imagine squeezing again. With only a little bit of pressure, the sharp point of the needle will pierce the skin. The reason for this is the physics of pressure, and it is the same principle behind the design of a spear (i.e. why spearheads are pointy rather than just the blunt end of a blunt pole), and indeed behind the blade of a knife. Put plainly, the same amount of force produces greater pressure when applied to a smaller area.

What Does The Blade Accomplish?

A knife’s blade accomplishes a cut by concentrating the force of the tool onto a very small surface area. As an edge is sharpened more finely, the contact surface area becomes smaller and smaller, and thus less pressure is required to accomplish a cut. Any professional chef or cook will tell you that a sharp knife is a safe knife, and it’s the dull ones you have to look out for. It seems counterintuitive until you consider the mechanics above. When you cut with a dull knife, the force is spread over a larger surface area and therefore requires more pressure to get through; more often than not, it’s when you force it that you’ll cut yourself. (Though of course a great deal of care and attention is required when working with a sharp knife.) 

What Else Is There To A Blade?

It is also worth noting that the blade of a knife comprises more than just an edge. While there isn’t a whole lot of “anatomy” to know about, there is more than you might think. The cross section is one aspect worth discussing. The cross section of a blade is the result of how the knife is ground, and it is the shape you would see if you cut straight through the blade anywhere along its length. While it can be a simple triangle, the shapes can also become much more complex. I have several types of contact surface available to me in my grinding, including a flat surface, several diameters of wheel, and an unsupported slack abrasive belt. Using these, I can produce flat grinds, hollow grinds, and convex grinds—as well as combinations thereof.

The cross section of a knife blade is also a major factor in the way the knife feels and performs. A hollow ground blade (ground against a wheel on both sides, so that both bevels are concave) typically features a fine and delicate edge; it would be ideal for a straight razor, but it would be completely useless for a machete. Similarly, a broad convex cross section is good for chopping because the edge is supported by a lot of material, but it would make a poor straight razor for the same reason. 

There are many other factors that determine how the blade of a knife will work. Steel choice, heat treatment, level of polish, serrations, etc., all play a role. As a knifemaker and bladesmith, I have to know how these factors play out and how they relate to one another in order to produce a knife that will suit its intended task. I design and craft the blade of each knife carefully, with all of these things in mind. We have come a long way from those stone tools.

About The Author

My name is Zack Jonas. I am a craftsman, and I take great pride in my work. There is nothing like the satisfaction that comes from turning raw, humble materials into an elegant and powerful work of functional art. I started Jonas Blade & Metalworks in 2007, and I have built it from the ground up as I worked to master my trade. I achieved the rating of Master Smith through the American Bladesmith Society, making me one of only 120 in the world. I see the achievement as a jumping-off point, a place to begin. There is so much more to learn and master, and a big part of my drive comes from a thirst to know more.