Cutting and slicing ability of knives

Many people believe – and this is prominent on social media and in various forums – that the cutting and usage properties of a knife are primarily determined by the type of sharpening. In other words, it is often debated whether:

• where to find,
• convex, or
• the knife should have a straight (FFG) edge.

(Of course, there are other types, such as chisel, katakiriba, skandi, etc., but these are the basics.) It is generally believed that the holkeres is the most fragile, the convex the thickest and most stable, and the straight is somewhere in between.

But this is only true – and not always clearly true – if all other conditions are exactly the same. These include blade thickness, the angle and thickness of the facet (edge band).

These factors are often overlooked, partly because they are harder to measure and less visible.

The following summary is based on several years of practical experience.

What are the characteristics that most affect the ability to cut?

So what are the other properties that affect the cutting properties of a knife?

• Thickness of the facet – how far down the leading edge is
• Edge angle – angle subtended by the pins drawn at the edge in the case of a convex edge
• Blade thickness – initial material thickness measured at the blade back

Practical experience has shown that the most noticeable difference is the difference in the thickness of the facet, i.e. the thickness of the grinding edge.

In the case of a convex edge, it is difficult to measure this precisely, but in fact if we imagine the convex as a straight-edged blade with an edge band whose edge is “flush-edged”, i.e. the planes of the leading and cutting edges are flush-edged either on a soft abrasive belt or on a vibrating belt, then it is perhaps possible to see that we can talk about facet thickness, even if a little more arbitrarily.

These properties (once again, the thickness of the facet, the angle of the edge band and the thickness of the blade) determine the cutting properties of a knife more than whether the section between the edge band and the two points on the blade back is straight, straight or, if applicable, convex. This is also an important attribute, but in my opinion the other attributes are generally more decisive.

Grouping of knives by use

For the interpretation of specific values, it is useful to group the knives by use. The following classification is simplified but can be used in practice. There are of course overlaps and individual preferences

Group 1 – fine cutting tasks

• Razors
• Carving knives
• Vegetable peeler knives
• Small knives and folders

Group 2 – general use

• EDC knives and folders
• Smaller fixed blade knives for everyday use (typically with blade thickness below ~4 mm)
• Kitchen knives (not cleavers and not tapping knives)

Group 3 – more demanding

• Outdoor knives (bushcraft, hunting etc.)
• Bigger and stronger EDC knives
• Utility knives

Of course, these categories can be further broken down, e.g. razors could be taken separately, but even within the outdoor category, they could be further subdivided into subgroups (e.g.: machete knives, etc.) However, if we remember these three categories, we can’t go very far wrong.

Let’s look at these more specifically, at the level of numbers in a table.

Typical size ranges

It is important to note that the thickness of the facet and the angle of the edge band do not always fall into the same category, and the above values are based on practical experience, but should not be considered a universal rule, as the specific application is always the determining factor. Each person should judge these properties of knives based on their own knowledge (not from online and other places).

The article is based on the writing and experiences of Imre Palcsesz, knife maker (angelero.hu). Thank you for sharing your professional experience!