If you find about kitchen knife basics,please looking for the cutting edge of your favorite chef's knife may seem to be a
smooth ridge of metal, but it's not. If you looked at it under a
microscope, you would see it was made up of very tiny - and very jagged
and uneven - teeth. Sort of like an ultra-fine roughed-up saw blade.
Depending on the quality of the steel the knife was hewed from, as well
as the fit and finish of its latest sharpening, these teeth might almost
disappear (under a microscope). On top of this, because the metal has
been ground to such a fine wedge, these teeth would be extremely thin.
Why is this helpful to know? Because it should alert you to how delicate, and susceptible to corrosion, a knife blade really is. It's not like a spoon or fork or some other totally polished kitchen implement. It's got a raw, unfinished component - the edge - that's continually being exposed to the elements. Exposed to hard surfaces, to acidic fruit juices, to water and air ripe for oxidation (i.e. rust), to all kinds of stuff it needs to be protected from. That's why it's so important not to let it bang around in a drawer, or soak in a pot, or lie unwashed in a puddle of pineapple juice.
What's Your Angle?
When you hear a kitchen knife pro say a knife has a 15-degree edge, they are not talking about the overall cutting edge of the knife, they are talking about only one side. To measure this angle - logically called the edge angle - you must draw an imaginary line through the center of the blade and measure from there to the outer side of the primary bevel. (The primary bevel is the surface on the blade where the metal has been ground down to form the cutting edge.)
The complete cutting angle of the knife (which is rarely referred to and is the sum of both edge angles) is called the included angle. Since most knife blades are ground symmetrically, in most cases, the included angle for a knife is simply twice the edge angle. Simple, huh?
German Knives: Knives manufactured in the German/Western tradition (e.g. Henckels and Wusthof and crew) are typically ground with a 20 to 22 degree edge angle. Which means that the actual knife (the included angle) is cutting with a 40-44 degree wedge. Doesn't seem that sharp, does it? It isn't. It's designed to be just sharp enough, yet take a ton of abuse. It can nick a bone and not chip, or saw its way through frozen pork tenderloin (something it should never be used to cut through in the first place) and still not crack or break. It's a warhorse.
Japanese Knives: Japanese knives (and Japanese hybrids) are factory ground with edges from 10 to 15 degrees. Which adds up to included angles of 20 to 30 degrees - the smallest of these creating a wedge half the size of the typical Western knife. Whoa. No wonder Japanese knives are all the rage - they make everything you slice feel like butter. But beware, there's no free lunch. Try abusing a Japanese knife and you will pay for it with chips and cracks galore!
Before we leave this discussion on angles, let me repeat that not all knives are created with two symmetrical edge angles. There are some notable exceptions - the biggest being the whole family of chisel-edged traditional Japanese knives which are beveled on one side only. One of the reasons they're designed this way is to take advantage of the geometry. Think about it. Instead of adding up two 15 degree angles to get an included angle of 30 degrees, their second angle is perpendicular (or 0 degrees), thus making the included angle (the total wedge of the knife) a screaming 15 degrees! That's almost three times the sharpitude of your typical German knife. That's scary sharp.
• • •
Take a tour of the kitchen knives you own. Can you correctly identify what kind of edges they all have? How are you currently storing them? Are you protecting them from getting damaged and dulled? Now that you know a little bit more about the nature of your kitchen knives' edges, hopefully it will inspire you to do your best to care for them. The better you protect and maintain your knives, the less you'll have to sharpen them and the longer they'll last.
Why is this helpful to know? Because it should alert you to how delicate, and susceptible to corrosion, a knife blade really is. It's not like a spoon or fork or some other totally polished kitchen implement. It's got a raw, unfinished component - the edge - that's continually being exposed to the elements. Exposed to hard surfaces, to acidic fruit juices, to water and air ripe for oxidation (i.e. rust), to all kinds of stuff it needs to be protected from. That's why it's so important not to let it bang around in a drawer, or soak in a pot, or lie unwashed in a puddle of pineapple juice.
What's Your Angle?
When you hear a kitchen knife pro say a knife has a 15-degree edge, they are not talking about the overall cutting edge of the knife, they are talking about only one side. To measure this angle - logically called the edge angle - you must draw an imaginary line through the center of the blade and measure from there to the outer side of the primary bevel. (The primary bevel is the surface on the blade where the metal has been ground down to form the cutting edge.)
The complete cutting angle of the knife (which is rarely referred to and is the sum of both edge angles) is called the included angle. Since most knife blades are ground symmetrically, in most cases, the included angle for a knife is simply twice the edge angle. Simple, huh?
German Knives: Knives manufactured in the German/Western tradition (e.g. Henckels and Wusthof and crew) are typically ground with a 20 to 22 degree edge angle. Which means that the actual knife (the included angle) is cutting with a 40-44 degree wedge. Doesn't seem that sharp, does it? It isn't. It's designed to be just sharp enough, yet take a ton of abuse. It can nick a bone and not chip, or saw its way through frozen pork tenderloin (something it should never be used to cut through in the first place) and still not crack or break. It's a warhorse.
Japanese Knives: Japanese knives (and Japanese hybrids) are factory ground with edges from 10 to 15 degrees. Which adds up to included angles of 20 to 30 degrees - the smallest of these creating a wedge half the size of the typical Western knife. Whoa. No wonder Japanese knives are all the rage - they make everything you slice feel like butter. But beware, there's no free lunch. Try abusing a Japanese knife and you will pay for it with chips and cracks galore!
Before we leave this discussion on angles, let me repeat that not all knives are created with two symmetrical edge angles. There are some notable exceptions - the biggest being the whole family of chisel-edged traditional Japanese knives which are beveled on one side only. One of the reasons they're designed this way is to take advantage of the geometry. Think about it. Instead of adding up two 15 degree angles to get an included angle of 30 degrees, their second angle is perpendicular (or 0 degrees), thus making the included angle (the total wedge of the knife) a screaming 15 degrees! That's almost three times the sharpitude of your typical German knife. That's scary sharp.
• • •
Take a tour of the kitchen knives you own. Can you correctly identify what kind of edges they all have? How are you currently storing them? Are you protecting them from getting damaged and dulled? Now that you know a little bit more about the nature of your kitchen knives' edges, hopefully it will inspire you to do your best to care for them. The better you protect and maintain your knives, the less you'll have to sharpen them and the longer they'll last.
Nate is the owner of KitchenKnifeGuru.com - a website
dedicated to educating the world about kitchen knives and how to keep
them sharp. To learn more (including an article titled The Sharpening Cycle), join him at http://www.kitchenknifeguru.com.
