Buck Raper on Knives

Buck Raper is the manager of manufacturing and engineering for Dexter-Russell, the largest and oldest cutlery manufacturer in the United States. Above, Buck holds a knife next to an edge sharpness and edge life test apparatus in their metallurgy lab.

How did you come to work at Dexter-Russell?

In a former life, I was working on a doctorate in synthetic organic chemistry.

Wow. What happened?

I got drafted to Vietnam.

And then you came back...

I came back and there weren’t many job opportunities for PhD chemists, and I was still looking at two more years in school, and I had a family to support. So I went and got an MBA and got twice the starting salary I would have gotten as a PhD. My family had always been in the cutlery business, my grandfather, and my father, and all I ever heard was knife talk. When I was a Baby Buck, my father would take me into the pocket-knife factory on Saturday mornings and hand me off to a foreman so he could get some work done, and I’d make knives with a foreman.

Did the background in chemistry, combined with your family’s history in knife making, complement each other?

To some degree...but it was more of the scientific method and analytical techniques that you learn in a hard science, applying them to manufacturing. I looked at it from a different standpoint than a history major MBA would, or an English major MBA would. Coming from a real science, you take a different approach, an engineering approach.

Can you give me an example?

Much of the heat treating, the grinding, and the choice of steels was done almost by folklore. It’s always been done that way and nobody remembers why. Now when we’re trying to choose a steel for a particular application, we do some testing, make some blades, and try them out to see what the results are. We have a control sample and record data. That’s the type of change that I made. Dexter-Russell is 192 years old, and we still have machinery and tooling that we were using at the turn of the century, from 1900. Those techniques still work and they’re still very good, but nobody really knew why we were doing things the way we were doing them.

What surprised you when you were testing the folklore?

We’re number one in professional oyster knives, and there’s the chronic problem with the tips of oyster knives breaking off. We had a heat-treatment process that we thought was making the steel hard enough to not break. The theory was if the blade is breaking, make it harder, and then the tip won’t break off. The reality was what we needed to do was to make tougher steel. So we changed our heat treatment process to create a tougher, softer steel.

What does it means for a steel to be tough versus hard?

It’s a trade-off to hold an edge. The harder the steel is, the better it will hold an edge. But you also want to have some flexibility. If you need a flexible bone or fillet knife, a harder steel is more brittle; it would fracture. So you have to trade off the hardness for the toughness that allows you some flexibility. The toughness also gives you wearability, resistance to abrasion. One way an edge fails is that you literally wear away the grains of steel, and to resist that, you’re looking for a tough steel.

When you heat-treat steel, you martenize it to the temperature that’s going to give you the maximum hardness. But if you underheat it, if you undercook it a little bit, it comes out tougher. If you overcook it, it’s also tough, but then it corrodes. In our case, when we’re talking heat-treatable stainless 400 series steel, the optimum temperature is 1934°F / 1057°C. If you heat it to 1950°F / 1066°C, you get the same hardness that you would if you heat it to 1920°F / 1049°C, but one is tougher, and the other will corrode.

Steel is formed of grains. If you were to snap a knife blade in half, and look at it with the naked eye, the texture would look like a fine cement inside the knife. What you’re seeing is groups of grains. Steel exists in 9 or 10 different phases. Depending on how it’s been processed, temperature-wise, it has a mixture of these various phases, and that determines the toughness of the steel. I use the analogy of baking a cake when I’m explaining heat treatment. You have raw dough and expose it to heat. There’s a chemical change and a phase change, and you go from slurry to a porous solid once it’s baked.

With steel, once it is heated to a critical temperature, cooling—called quenching—is also critical. You’ve probably seen old movies where the blacksmith is pounding away, when he gets the iron hot, he plunges it into the water and there’s a hiss of steam. The reason for that is the rapid cooling. In the case of stainless steel, you have to get it below 1350°F / 732°C in less than three minutes in order to maintain the phase that you want. If you cool it slower, you get a different mixture of phases in the steel. So it’s not just in bringing it up to temperature, the cooling curve is key.

Steel is also determined by the alloy. There’re two or three dozen different types of stainless cutlery steels, and stainless cutlery steels are just a very small subset of alloyed steels. Alloyed steels are a subset of carbon steels. And all the heat-treatment processes are determined by which alloy you’re working with.

Are there other types of steels that you would want to use for particular purposes for knife making?

We want to use a stainless steel, although carbon steel makes wonderful knives. Everybody likes their old carbon steel knives, but nowadays, with the National Sanitation Foundation and other regulatory bodies, you can’t use carbon steel knives in most restaurants. We choose stainless, which has chromium in it; the chromium makes it stainless. You also have to have carbon in the steel so that you can harden it. You add more carbon if you want to create a harder blade, and more chromium if you need to get more corrosion resistance. When you heat-treat it, you want to come out with a very fine texture, and things like molybdenum, vanadium, tungsten, and cobalt help you get a fine grain. Tungsten and cobalt help make the steel tougher.

What’s the rationale prohibiting carbon knives in restaurants?

They rust, and rust is iron oxide. It’s dirty, and where the blade has rusted, there are pits that will retain grease. The grease will breed bacteria. It’s usually controlled by city or state or county ordinance.

Carbon steel versus stainless steel. Which is better?

That was a classic question that I wondered about for 30 years. I finally had a seminar with a metallurgist from a French steel mill, and he developed a machine to test the sharpness of edges and the life of edges. The answer is that you can get a carbon steel edge about 5% sharper while a stainless steel edge will last about 5% longer. With stainless steel being tougher, it is harder to create the edge, so stainless steel often gets a bad reputation because people can’t sharpen it correctly. It is possible to get carbon steel 5% sharper, but you would never perceive that using a knife. You need the scientific apparatus to bring out that difference. The practical difference is it’s very easy to bring up an edge on carbon steel, so most people’s carbon steel knives are sharper because they’re easier to resharpen. A carbon steel knife responds very easily to a butcher’s steel; you have to work a little bit more with a stainless steel knife.

I’m going to ask the question that’ll probably lead to the gates of Hell: how do I sharpen a knife correctly?

There are lots of ways to do it. Probably the best general-purpose way and what I recommend to people is to use a diamond sharpening steel. The traditional serrated butcher’s steel is a ½″ or ⅝″ rod with ridges running longitudinally. Those are now being replaced by rods that are plated with diamond. The diamond rod brings up an edge very quickly, because it’s hard enough to remove metal, creating a new edge.

An edge is actually a whole bunch of little burrs, sort of like hacksaw teeth that are standing up, perpendicular to the back of the blade. When you cut, those little burrs (here we call them feathers) roll over. The first thing that happens when you swipe with a butcher’s steel is you stand those feathers up, and you have a real good edge. After a time, they bend back and forth. They work-harden and break off, like breaking a wire by twisting it until it work-hardens and snaps. Then you have to create a new edge, new burrs, and the grit on a diamond steel is perfect for that. That’s what the long serrations do on your regular butcher’s steel, but it’s a lot easier to do with a diamond steel.

When you run a knife edge along a steel, you stand up the burrs, and you start thinning down the edge. I can do it with the back of a porcelain plate, or I can rub a knife on a brick wall and bring up the edge, but a diamond steel is best.

I’ve made a lot of trips to China, and they have very primitive kitchens as far as equipment, tools, and utensils go. They make do with the one basic knife. People call it a cleaver, but it’s not really a cleaver. It’s a slicer and a spatula and a scraper and everything else, but with that one knife, they stop and squat on the floor and bring the edge back on a brick that’s in the floor. They keep those knives very, very sharp. I learned in Chinese cooking how nicely things are sliced up counts as much as the taste, the presentation, and the freshness of ingredients. All of that can be ruined if you have cut raggedy chunks.

I would recommend either a diamond butcher steel or a whet stone. But a whet stone takes more skill, more training to use. I would stay away from electric sharpeners.

At some point the burrs snap off, and I presume that’s the point at which one needs to actually grind down the edge of the knife to form a new edge?

With a diamond steel, you’re doing grinding at the same time you’re straightening up the edge. A traditional butcher’s steel isn’t hard enough to remove metal. The deal with using a butcher’s steel is your steel has to be harder than the metal of the blade you’re sharpening. Otherwise, you get nowhere, like using a common file to smooth or shape metal. Your file won’t cut the metal if the file isn’t harder than the metal it’s cutting. If you let your knife get very dull, bringing the edge back is a real bear. If you give it a few strokes on a butcher’s steel every other day, or once a week, or every time you go to put the knife in the drawer, then the knife is always ready.

At what point is a knife effectively used up? [Buck shares with me the photo shown below.] I cannot believe how much the bottom knife has been sharpened away compared to the new knife on top. What’s the story with this actual knife?

Whoever was resharpening that knife was very, very good. It came back to our customer service people for replacement from a mom-and-pop butcher shop. I train our sales force, and one of the questions they ask is how long is a knife useful. I show them this. That’s pushing the ridiculous. I would think that that knife had seen about five or six years of service.

We usually find in a restaurant that a knife is good for six to nine months. With professional cutlery, and in particular with packing houses, they’ll need a wide blade for breaking down a side of beef. They need a large curved knife, which we call a cimeter steak knife. When it starts out life, it’s about 2 1/2″ wide, and when it gets down to about 1″ or 1 1/4″ wide, it’s no longer suitable for breaking down the big sides of beef. So then they use it for the smaller cuts, and call it a breaking knife. When they wear it down to about under an inch, they use it as a boning knife.

So these knives actually go to a series of different lives? As they get smaller from sharpening, they get repurposed and reused?

They get narrower, and they get shorter. People find different applications for them. The poultry industry still does that. What I’m talking about is mostly pre-WWII. After WWII, people started coming to us and saying, “Hey, can’t you make this shape from scratch?” So we started to create the same shape as the worn-out knife. You wouldn’t have to wear out a giant cimeter; you could just buy a breaking knife off the shelf. A lot of our traditional knife shapes have evolved from large blades that were worn down and used for different applications, and then we started making a blade with that shape.

What advice would you give somebody new to the kitchen?

If I were being a smartass, I would tell you don’t run with a knife. Keep your knives out of the dishwasher. Wipe them clean with a damp rag. When you put them in the dishwasher, they bang together and you nick up your edges. If you do put them in the dishwasher, make sure you pull them right out of the basket and dry them off. Keep up with your sharpening; don’t let your knife get dull. Maintain the edge every time you use it or every other time you use it. Give it one or two strokes on a steel and sharpening will never be a chore, and you will always have a sharp knife.

Knife Sharpening 101

Keeping your knives sharp is the kitchen equivalent of backing up your files: it’s something you should do more often than you think. A sharper knife is safer and easier to use:

  • Sharp knives require less pressure for making cuts so there’s less force involved—meaning you’re less likely to slip and cut yourself.

  • Sharp knives cut cleaner; there is less “tear” through whatever you’re cutting.

  • Sharp knives keep your arm from getting tired because you don’t have to muscle through things. Of course, you’d probably need to be slicing and dicing for many hours to notice.

Keeping your knives in good working order involves both keeping the blade “true” (in alignment) and grinding down the blade to reshape the edge if the trued shape is lost. To keep your knives true, use a sharpening steel (those steel rods ubiquitous in celebrity chef photos) as part of your cleanup and wash routine at the end of a cooking session. By running the knife against the sharpening steel, you push any portion of the edge that is out of alignment (“burrs”) back into alignment. (Never try to true a serrated knife, such as a bread knife—the sharpening steel won’t fit against the serrated edge.) Look for a diamond-coated sharpening steel; the diamond coating is harder than the steel, so it can not only realign the burrs but also create a new edge, keeping the knife truly sharp and actually removing the need to reshape the edge.

More serious sharpening involves grinding down the blade to form a new edge and can be done against any hard surface: a sharpening stone, a grinding wheel, even a brick! (See the interview with Buck Raper on the preceding pages for details.) If it comes to that, I find it easier to have my knives professionally sharpened. Grinding down the edge isn’t a great thing, though, because creating the new edge removes material. Knives used in restaurants can be “sharpened through” in under a year—that is, sharpened down to a point where the new edge on the knife becomes too thick to hold a sharp edge for long.

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