Post by Lobster on Jan 31, 2016 19:31:16 GMT 3
Blade geometry
This describes the relationship between the ability to cut and the strength of a blade's edge. The following characteristics determine the blade geometry:
Blade Thickness
Blade thickness is important to both strength and cutting ability of the knife. A thick blade will generally be stronger but a thin blade will generally cut better. So the choice of blade thickness is driven by the compromise of strength vs. cutting ability.
The grind type can reinforce the attributes of the stock or to a degree make up for any weakness. For example, a thick blade can have a flat or hollow grind so that even though the spine is thick & strong, the edge is thin and cuts better. On a thin blade, a saber grind can be used to make the edge stronger.
Edge Thickness
The thickness of the edge is another trade off in strength vs. cutting ability. The thinner the edge, the better it cuts but a thin edge is weak and can chip or roll easier. A thick edge is strong, but doesn't cut as well.
The Bevel
Some blades have one bevel, some have two. On the graphic below you can see that grind Nr. 2, 5, 6 and 7 have all 2 bevels with the primary bevel starting from around the middle of the blade going almost all the way down to the edge. At the very edge itself and at a higher angle, there is the secondary or micro bevel that forms the actual edge. Most standard production knives have one of those kinds of geometry, where a shallow primary angle meets a bigger secondary angle. This leave the edge a bit thicker for added strength.
Some knives with Scandinavian and Zero grinds only have a single bevel. Because the primary bevel goes all the way down to the edge, you end up with a very thin, high-performance edge that cuts really well but these edges are also a bit weaker. Some chisel-ground knives also feature a primary-bevel edge.
The Grind
The grind of a blade refers to the shape of the cross-section of the blade as shown below and is distinct from the shape of a blade.
1 Zero grind
Not a very common grind, has no secondary bevel, the bevel is what you grind. Difficult to sharpen without scratching the finish of the blade, takes a keen edge but it is quite delicate and not suitable for heavy use.
2 Chisel grind
As on a chisel, only one side is ground whilst the other remains flat all the way to the spine. Many Japanese kitchen knives come with a chisel grind. Knives which are chisel ground come in left and right-handed varieties. A downside is that they tend to cut towards one side depending on where the bevel is thus making straight cuts more challenging.
3 Scandinavian/zero grind saber
Easy to produce, it is often used on thin blade stock to maintain more material behind the edge improving the strength of the edge.. Can be made very sharp, often used on classic woodworking and bushcraft knives.
4 Convex grind
Usually found on larger knives requiring a thick blade stock. Rather than tapering with straight lines to the edge, the taper is curved. Such a shape keeps a lot of metal behind the edge making for a strong edge while still allowing a good degree of sharpness. Frequently used on axes it is sometimes called an axe grind. Not easy to sharpen due to the changing angles.
5 Hollow grind
A very common grind used extensively in mass produced knives. A concave hollow is removed from both sides of the edge producing a very sharp but thin edge. More prone to rolling or damage than other grinds and not so suitable for heavy chopping and cutting hard materials
6 Full flat grind
The blade tapers on both sides all the way from the spine to the edge meaning that a lot of metal is removed from the blade. Can be made very sharp but is difficult to sharpen and doesn't hold an edge very well. It sacrifices edge durability in favor of more sharpness.
7 Saber grind
The saber grind has a strong edge. The bevel starts around the middle of the blade, and proceeds flatly towards the edge. This leaves a strong edge for chopping and other hard use. But it also means the edge will be fairly thick, so this design will not necessarily slice all that well.
This describes the relationship between the ability to cut and the strength of a blade's edge. The following characteristics determine the blade geometry:
Blade Thickness
Blade thickness is important to both strength and cutting ability of the knife. A thick blade will generally be stronger but a thin blade will generally cut better. So the choice of blade thickness is driven by the compromise of strength vs. cutting ability.
The grind type can reinforce the attributes of the stock or to a degree make up for any weakness. For example, a thick blade can have a flat or hollow grind so that even though the spine is thick & strong, the edge is thin and cuts better. On a thin blade, a saber grind can be used to make the edge stronger.
Edge Thickness
The thickness of the edge is another trade off in strength vs. cutting ability. The thinner the edge, the better it cuts but a thin edge is weak and can chip or roll easier. A thick edge is strong, but doesn't cut as well.
The Bevel
Some blades have one bevel, some have two. On the graphic below you can see that grind Nr. 2, 5, 6 and 7 have all 2 bevels with the primary bevel starting from around the middle of the blade going almost all the way down to the edge. At the very edge itself and at a higher angle, there is the secondary or micro bevel that forms the actual edge. Most standard production knives have one of those kinds of geometry, where a shallow primary angle meets a bigger secondary angle. This leave the edge a bit thicker for added strength.
Some knives with Scandinavian and Zero grinds only have a single bevel. Because the primary bevel goes all the way down to the edge, you end up with a very thin, high-performance edge that cuts really well but these edges are also a bit weaker. Some chisel-ground knives also feature a primary-bevel edge.
The Grind
The grind of a blade refers to the shape of the cross-section of the blade as shown below and is distinct from the shape of a blade.
1 Zero grind
Not a very common grind, has no secondary bevel, the bevel is what you grind. Difficult to sharpen without scratching the finish of the blade, takes a keen edge but it is quite delicate and not suitable for heavy use.
2 Chisel grind
As on a chisel, only one side is ground whilst the other remains flat all the way to the spine. Many Japanese kitchen knives come with a chisel grind. Knives which are chisel ground come in left and right-handed varieties. A downside is that they tend to cut towards one side depending on where the bevel is thus making straight cuts more challenging.
3 Scandinavian/zero grind saber
Easy to produce, it is often used on thin blade stock to maintain more material behind the edge improving the strength of the edge.. Can be made very sharp, often used on classic woodworking and bushcraft knives.
4 Convex grind
Usually found on larger knives requiring a thick blade stock. Rather than tapering with straight lines to the edge, the taper is curved. Such a shape keeps a lot of metal behind the edge making for a strong edge while still allowing a good degree of sharpness. Frequently used on axes it is sometimes called an axe grind. Not easy to sharpen due to the changing angles.
5 Hollow grind
A very common grind used extensively in mass produced knives. A concave hollow is removed from both sides of the edge producing a very sharp but thin edge. More prone to rolling or damage than other grinds and not so suitable for heavy chopping and cutting hard materials
6 Full flat grind
The blade tapers on both sides all the way from the spine to the edge meaning that a lot of metal is removed from the blade. Can be made very sharp but is difficult to sharpen and doesn't hold an edge very well. It sacrifices edge durability in favor of more sharpness.
7 Saber grind
The saber grind has a strong edge. The bevel starts around the middle of the blade, and proceeds flatly towards the edge. This leaves a strong edge for chopping and other hard use. But it also means the edge will be fairly thick, so this design will not necessarily slice all that well.