Metalworking -BLACKSMITH Knife Maintenance And Sharpening.pdf

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eG Forums _ The eGullet Culinary Institute (eGCI) _ Knife Maintenance and

Sharpening

Posted by: eGCI Team on Aug 13 2003, 07:05 AM

Knife Maintenance and Sharpening

By Chad Ward (Chad)

Warning : Remember that handling, using and sharpening knives is inherently dangerous. Neither

eGullet nor the author can be responsible for your safety. That’s your job. Knife safety, especially

during sharpening, is a matter of common sense. Keep your fingers, toes and everything else out of

the path of the blade – even if it were to slip. If you go slowly, pay attention and stay focused, you’ll

be fine.

Table of Contents

Introduction

Section One: The Sad Truth about Kitchen Knives

Section Two: Steel

Section Three: Edge Basics

Section Four: Sharpening Basics

Section Five: Sharpening Step by Step

Section Six: Maintenance

Section Seven: Overview of Sharpening Systems

Section Eight: Conclusions and Resources

Introduction

“Knife sharpening is hard.”

“Sharpening is too difficult and time consuming to do at home.”

“Send your knives to a professional sharpener once a year and you will be fine.”

“You have to spend hours hunched over a heavy hone slathered with oil.”

This well-intentioned advice is parroted in cooking schools, Food Network television programs,

professional manuals and cookbooks. And it is just plain wrong.

Okay, maybe not so much wrong as misleading.

Knife sharpening is not difficult. It is not shrouded in mystery. With a little knowledge, a little

geometry, a couple of tricks and some inexpensive tools, knife sharpening can be fairly easy and

extremely rewarding. At the very least it’s a great skill for the toolbox. You’ll come away from this

clinic with a better understanding of edges, steel and how to maintain your knives yourself. Or, if

you decide to send them out, you’ll know how to make sure you’re getting what you want – and

what you pay for.

Section One: The Sad Truth About Kitchen Knives

To a chef, there is nothing more important than his knife. It is not only an extension of his hands, it

is an extension of his very personality. The knife is a chef’s paintbrush.

So why are most kitchen knives so bad?

The knives found in most commercial and home kitchens are designed for the lowest common

denominator. The manufacturers of these knives make a series of compromises calculated to keep

the largest number of people happily using their knives for the longest period of time. Like

supermarket tomatoes bred for sturdiness and uniformity rather than flavor, these compromises

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seriously degrade the performance of your knives.

The first compromise begins with the steel. Steel is the heart of the knife. Most manufacturers

(Henckels, Wusthof, Forschner, et al.) have proprietary steel blends and are very close-mouthed

about the actual formulation of their steels. According to industry insiders, these steel blends are

closely related to or equivalent to a steel known as 440a. By and large 440a steel is formulated for

stain and wear resistance rather than holding a high performance edge.

In the kitchen, that’s not a bad tradeoff.

But this compromise in edge performance is compounded by a heat treatment that leaves the steel

much softer than it could be. In general, the harder the steel, the keener the edge it will take.

However, a hard steel makes it more difficult to get that edge in the first place. So manufacturers

leave the steel a little soft, theoretically making sharpening at home easier. If you’ve ever spent an

hour or two trying to get a super fine edge on a cheap kitchen knife, you’ll know that there is a big

gap between theory and practice.

Upper-end kitchen knives like Henckels, Sabatier, Wusthof, et al., are a little better, but are still

softer than they need to be at 52 to 56 on the Rockwell C scale (the

http://www.wikipedia.org/wiki/Rockwell+scale is a scale used to measure the relative hardness of

different solids). By contrast, Japanese knives tend to be around 61-62 on the Rockwell scale.

Custom knife maker Phil Wilson hardens his S90V (a stainless supersteel) chef’s and filet knives to

62-63 Rockwell.

The next compromise is in the factory edge angles. Most kitchen knives come with an edge that is at

least 25 degrees per side, frequently even greater. If you add the two sides together you get a 50

degree included angle. And that’s the best case scenario. Take a look at a protractor if you happen

to have one lying around. Fifty degrees is extremely thick. An angle that obtuse is more appropriate

for an axe than a chef’s knife. Again, the theory is that the thick angles will allow the edge to resist

damage from impaction, rolling and wear better than a thin edge. But, as the song says, it ain’t

necessarily so.

Finally, there is just plain cruelty and misuse. While I’m certain none of you would ever use the

sharpener on the back of an electric can opener, or use a glass cutting board, or store your knives

loose in a drawer or put them in the dishwasher, it does happen. And when you add soft steel and

thick angles to the general abuse that knives see in the kitchen, you end up with tools that are more

adapted for bludgeoning oxen than fine dicing a soft tomato.

Take heart. The news isn’t all bad. We can fix these problems. Geometry is far more important than

steel. With some basic knowledge and the willingness to invest a little time, you can realistically

expect a dramatic increase in knife performance.

First, do no harm: General knife care

- Use wooden or composite plastic cutting boards only. Glass, ceramic, marble and steel will cause

the edge to roll or chip. Bad. Don’t do it.

- Don’t drop your knives in the sink. Not only is it a hazard to the person washing dishes, but you

can also blunt the tip or edge.

- Don’t put your knives in the dishwasher. The heat may damage wooden handles and the edges

may bang against other cutlery or plates.

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- Keep your knives clean and dry. Sanitize if necessary.

- Do not store your knives loose in a drawer. Use a block, magnetic strip, slotted hanger or edge

guards. The magnetic strip is not recommended if you have children or inquisitive pets.

- Finally, your knife is not a can opener, a screwdriver, a pry bar, box cutter or hammer. There’s a

special place in Hell reserved for people who abuse their knives this way.

If your knives won’t fit in a block, simple plastic blade guards are a good solution

Second: Modify for performance

This is the easy part. Establishing and maintaining high performance edges is what this tutorial is all

about. It can be as simple as steeling with the proper technique or as complex as creating specific

edge bevel and edge aggression strategies for each knife in your collection. It’s all up to you.

While you can’t change the steel your knife is made from, you can certainly keep your knives at

peak performance – and without too much difficulty. We’ll discuss high performance edges and

sharpening strategies a little later in the tutorial.

Third: Modify for comfort

This is something very few chefs (and even relatively few knife makers) take into consideration. Ask

any chef to show you his knife-hand calluses. He’ll have a thick one at the base of his first finger

from the “pinch grip” used in most kitchens. He or she may also have another on the side of the

second finger where the finger rubs against the bolster or dropped portion of the blade that extends

below the handle.

He will also have aching hands and possible repetitive stress injuries.

In the interest of economy, most knife manufacturers leave the spines of their knives squared off.

The edges of the spine can sometimes be sharper than the knife itself. That edge cutting into your

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finger can lead to blisters, calluses, reduced circulation, numbness and injury.

If you ever handle a chef’s knife made by Canadian knife maker George Tichbourne you’ll know that

it doesn’t have to be that way. Tichbourne worked with several professional chefs when designing

his kitchen knife series. One of the key features is a smoothly rounded spine. It doesn’t abrade your

finger, cut off the circulation, make your hands numb or create any of the other discomforts

associated with standard kitchen knives.

You can do the same in less than half an hour. Lock your knife, edge down, into a padded vise. The

padding doesn’t have to be anything elaborate. Two pieces of flat rubber or leather will keep the

jaws from scratching the blade. You’ll need a sheet of fine (600 grit) wet/dry sandpaper available at

any auto supply store or an abrasive cloth, sometimes called a crocus cloth. Using a gentle

shoeshine motion, lightly round the edges of the spine. You don’t have to buff hard or remove a lot

of metal. All you need to do is break the sharp edge at the base of the spine. How far you take it is

up to you. This simple modification will make a world of difference in the comfort of your knives.

Section Two: Steel

An Overview of Steel

By definition, steel is a combination of iron and less than 2 percent carbon. For centuries, carbon

was the only alloying element. The problem in the early days of steel making was getting rid of

unwanted elements, not adding new ones. However, there are a variety of alloying elements that

are added to modern steels to impart various characteristics.

Iron alone is relatively soft. It does not hold an edge well, wears quickly and has little resistance to

bending. Add a little bit of carbon and the story changes dramatically. The carbon combines with the

iron to form hard carbide platelets cemented together in a matrix of iron. The combination is

resistant to wear and bending and will take a keen edge.

Smaller carbides and a tighter grain structure allow for a stronger, sharper edge. Other carbide

formers, like vanadium, can refine the grain of the steel further. Knives with a high vanadium

content can take a very keen edge, but are harder to sharpen.

Carbon - Present in all steels, it is the most vital hardening element. Greater than 0.5 percent

carbon content qualifies a steel as a “high carbon” steel.

Chromium - Added for wear resistance and corrosion resistance. A steel with at least 13 percent

chromium is considered “stainless.” Chromium is a carbide former, so it also increases wear

resistance.

Manganese - A carbide former. Manganese aids grain structure, increases hardenability, and wear

resistance. Manganese is present in most cutlery steels.

Molybdenum - Another carbide former. Increases hardness, prevents brittleness, makes the steel

easier to machine.

Nickel - Adds toughness and possibly aids in corrosion resistance.

Phosphorus - Essentially a contaminant.

Silicon - Increases hardness and strength.

Sulfur - Increases machinability but decreases toughness.

Tungsten - Increases heat, wear and shock resistance. Tungsten is the strongest carbide former

behind vanadium.

Vanadium - Another carbide former. Contributes to wear resistance and hardenability. Vanadium

refines the grain of the steel, which contributes to toughness and allows the blade to take a very

sharp edge.

Most kitchen knives fall into the category of “high carbon stainless.” These knives generally contain

between 0.5 and 0.8 percent carbon, 13 to 18 percent chromium and a little manganese,

molybdenum, silicon, phosphorus and sulphur. This makes for a steel that is easy to produce, is very

stain resistant and reasonably wear resistant. Knives from Global and Mac’s Superior line have some

vanadium added for improved wear resistance and a finer grain, which allows the knife to be

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sharpened to an incredible edge.

Carbon Steel versus Stainless Steel

The great debate rages on. Carbon steel advocates claim that their knives take a keener edge, hold

it longer and are easier to resharpen than stainless steel knives. Stainless steel users claim that

carbon steel knives are unsanitary, leave an off taste in foods and that stainless knives hold an edge

longer than their carbon counterparts.

Who’s right? Depends on your definitions and your environment. It’s not as simple as carbon versus

stainless.

Carbon steels range from simple iron/carbon combinations to high-alloy tool steels that will cut

through concrete without losing their edge. Stainless steels vary from very soft, extremely stain

resistant dive knives to super stainless alloys, like Crucible Particle Metals’ S30V, a steel

purpose-designed for the custom cutlery industry.

In the far less demanding realm of the kitchen, however, the carbon steel devotees are right. At

least until they actually have to use their knives. Then it’s a different story.

Carbon steel kitchen knives generally are a little harder and stronger than stainless steel kitchen

knives. They are easy to sharpen and take a screaming edge. And while the patina that develops on

a carbon knife can be unsightly (unless you like that sort of thing), it isn’t unsanitary.

But in the wet, acidic environment of the kitchen, stainless rules. For all their faults, compromises

and shortcomings, stainless steel kitchen knives work better and will hold their edges longer than

carbon steel knives.

Doesn’t make sense, does it?

The culprit is corrosion – the effect of acid and micro-rusting. Even on what appears to be a

mirror-bright, razor sharp edge, microscopic particles of rust and corrosion will form, attacking the

edge and reducing its performance. Unless carbon steel knives are rinsed and dried frequently, their

edges will degrade rapidly in kitchen use. The stainless edge will easily outlast them.

According to chef and knife maker http://www.haslinger-knives.com/, “Acids of fruit and vegetables

are fairly aggressive and will dull a carbon blade more quickly than stainless. The acid actually eats

the edge.”

Section Three: Edge Basics

Most kitchen knives are flat ground, meaning that the blade tapers directly from the spine to the

edge. Hollow ground, convex ground and saber ground blades are rarely found in the kitchen. I

mention them only to confuse you.

Edges come in a variety of flavors. The most common are the V-edge, double beveled edge, chisel

ground edge and the convex edge.

V-edges and double beveled edges are variations on a theme. The edge found on your kitchen

knives is most likely a V-edge, meaning, oddly enough, that the edge bevels form a V, two surfaces

intersecting at a line of (ideally) zero width.

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