Introduction
The blade shape is the essence of any knife. It defines its personality, strengths, weaknesses, and how it handles in your grip. Making the right choice can be the difference between a valuable tool and a useless one.
Understanding blade geometry goes beyond looks; it is science, every curve, angle, and edge plays a role in how efficiently the blade works in different situations.
In straightforward terms, blade geometry refers to how a knife’s cutting surface is designed, including factors like thickness and spine curvature. Delving into these details in a knife-making course can be invaluable when crafting your own blades.
What Is A Blade Profile?
Blade profile data describes the blade’s shape and strength. It is recorded at various points along the blade’s length. Importantly, this data remains consistent, regardless of how the length is divided into sections or segments.
How Does The Size And Shape Of The Blade Affect Performance?
When we talk about the shape of a blade, the profile usually comes to mind first. Two other key characteristics are the shape of its cross-section—the grind—and the ground angle and shape of its cutting edge—the bevel.
Look at the knife straight from the handle towards the tip to see the cross-section of its profile. The angles at which the blade surfaces have been sharpened from its spine to the cutting edge. The grind is how the blade is thinned to reveal the cutting edge.
To simplify it here for clarity, each category has variations.
Asymmetrical or combined grinds have nearly endless possibilities. The cross-section combines surfaces sharpened at different angles. The primary and secondary bevels form the blade’s final shape.
A blade’s cross-section determines its thickness and shape. The strength and pressure needed for cutting, and how the knife pushes away chopped food.
When blacksmiths decide on a blade’s geometry, they consider two key factors: the knife’s intended use and the steel’s strength.
- The thinner the blade, the better it will cut through food with less drag. However, a thin blade is more vulnerable. The cross-section should match the knife’s main purpose.
- A thicker blade is more durable, but less sharp. While a thinner grind ensures sharpness but decreases durability, each grind excels at specific tasks, so choose the grind and thickness that suit your needs.
Profiling or grinding creates the blade’s cross-section. This process removes a lot of material, determining the blade’s thickness and geometry, and thus its cutting characteristics. The grind affects how long a blade holds its edge and how it can be sharpened.
Regular sharpening thickens the profile cross-section. To maintain its intended use, we must refine it to improve cutting performance and reduce the strength needed to cut through food.
Single-Bevel Blade
- Chisels
- Traditional Japanese kitchen knives: yanagiba, deba, usuba, and kiritsuke
- Scissors
Single bevel, or chisel bevel, blades allow for precise cuts and are easy to resharpen. One side is flat, while the sharp side tapers in a straight line to the edge. Depending on which side the blade is on, these knives are designed specifically for either right- or left-handed users.
Double-Bevel Blade
A double-bevel blade consists of four surfaces:
- two parallel surfaces at the upper part of the blade
- two surfaces that meet at the edge.
- Double-bevel blades can usually be used with either hand.
- If sharpened asymmetrically, they can be specialised for either right- or left-handed use.
Check this out:
https://sharpedgeshop.com/blogs/knives-101/blade-construction-geometry
Why Is Blade Profile Important While Designing?
The blade shape, or blade profile, plays a vital role in your cutting technique. There is no universal “good” or “bad” profile; it is just what suits you best. Take, for instance, the convex profile, also known as hamaguri. It offers superior sharpness and prevents food from sticking, thanks to its careful design.
What Is The Best Blade Shape For Everyday Use?
The drop point blade stands out as one of the most popular shapes. It features a gently curved spine that slopes down to meet the point. This design results in a robust and wide tip, perfect for tasks demanding precise and controlled cuts.
What Are Western Double-Bevelled Knives?
Western knives are typically double-bevelled, with a consistent angle along the blade’s sides (a flat, convex grind from the spine to the cutting edge). They often feature a V-grind with a 30-degree cross-section and a 15-degree grind.
Double bevel knives can be put in a group according to their cross-section and where the shinogi line is. (where the angle of the surface changes):
- Concave
- Convex
- Flat
Concave Profile or Hollow Grind The blade below the shinogi line has a concave shape. Hollow grinds end in a very thin, extremely sharp point, the thinnest among double-bevel knives. These blades stay sharp for a long time, even with frequent sharpening. This thin profile makes the knife feel sharp even when it’s ready for sharpening.
Convex Profile or Hamaguri Convex grinds, also called hamaguri (clam-shaped edges), are the most challenging to produce due to their outward bowing edges. Derived from katana blades, they offer superior sharpness, require delicate handling, and help prevent food from sticking. This shape maintains a lot of metal behind the edge, making it stronger yet sharper. However, reproducing this grind is difficult for anyone other than an experienced sharpener.
Flat Profile, V-Edge, Scandi, or Sabre The blade tapers from the spine to the edge on both sides at a common angle, with variations based on shinogi line placement. Flat grinds are common on Japanese knives and many kitchen, hunting, and tactical knives. They produce very sharp edges, ideal for thin slices, balancing cutting ease and robustness. However, flat edges dull more quickly and can thicken with frequent sharpening.
Distal Taper Developed by Smiths, this concept describes the blade thinning from the heel to the tip. The knife is heavier and stronger at the handle (for more pressure) and thinner and more precise at the tip, allowing for smooth, precise cuts and easy manoeuvrability.
Understanding the science behind knife making opens up a world of precision and craftsmanship. Each element of blade geometry, from single and double bevels to various profiles and grinds, plays a crucial role in a knife’s performance.
Whether you are a professional chef, a home cook, or an aspiring knife maker, looking into these details can transform your appreciation and skill with knives. Learning about blade shapes and geometry, will not only enhance your cutting experience but also gain a deeper respect for the art and science that go into crafting each blade.
People Also Ask
What is the best blade shape for a knife?
The drop point, popularised by knife maker Bob Loveless, is the most common and popular modern blade shape. Named for its sloping spine that “drops” into the tip, it’s widely used for its versatility and practicality.
Why are knives shaped the way they are?
The broad, slightly curved belly of the blade is intentionally designed to facilitate a rocking motion when cutting. This enhances precision and efficiency, making tasks such as chopping herbs, mincing garlic, and dicing vegetables effortless.
What is the cross-section of a knife?
The cross-section of a blade results from surfaces sharpened at various angles, such as the primary and secondary bevels. These elements combine to define the ultimate shape of the blade.
What Angle Should You Sharpen A Double-Bevel Knife?
A double-bevel knife can be sharpened within the range of 20 to 30 degrees on each side. Opting for a higher angle, like 30 degrees, is advisable for tasks like chopping or cutting dense meats and vegetables, as it enhances durability.
What is the cross-section of a blade?
In simple terms, slicing a blade in half crosswise reveals its cross-sectional design. Early Viking and medieval European blades typically featured a lenticular cross-section.
Author: Janice van der Westhuizern