How to Sharpen a Serrated Knife, According to a Professional Knife Sharpener

A top-notch serrated knife is an essential kitchen tool—in fact, it may be even more useful than a chef's knife or paring knife. It also stays sharper for longer than your other knives (since less of its blade hits your cutting board), and its jagged edge allows it to slice effortlessly through produce and crusty baguettes alike. But, like your other kitchen tools, a serrated knife can become dull over time. We spoke with an expert craftsman to learn how to sharpen a serrated knife and keep it in top condition.

What Is a Serrated Knife?

A serrated knife—also known as a bread knife (yes, they're the same thing!)—has a long, thin blade with sharp, jagged teeth. Serrated knives designed for culinary use have serrations of about 30 degrees, compared with serrated knives used for other purposes that have narrower ridges. Only one side of the blade is serrated; the other side is sharp but flat.

Size

Most serrated knives measure between 4 1/2 to 10 inches long, but some serrated knives for cutting cakes measure around 18 inches.

Steel Origins

The best serrated knives are made from German or Japanese steel, which is higher quality than Chinese steel, says Enrico Casatelli, the owner of Knife Sharpening of Bergen County. Here's how they stack up:

Chinese steel: The edges of knives made from Chinese steel often disintegrate when you try to sharpen them, he says; it's more cost-effective to buy a new knife than it is to sharpen them.

Japanese or German steel: By comparison, a quality serrated knife made from Japanese or German steel can cost as little as $50—and can be sharpened repeatedly.

When to Use a Serrated Knife

You know to reach for a bread knife when slicing crunchy baguettes and rustic sourdough boules, but the tool also makes quick work of any produce with a tough exterior and soft interior. Tomatoes, eggplant, and even watermelon—along with delicate produce that tends to get squashed during food prep—are best to cut with a bread knife because it can "bite" through the skin.

When to Sharpen a Serrated Knife

The specific timing depends on how often you use your serrated knife and how well you maintain it. "With any knife, you know it's not sharp when you try to cut an onion or tomato and you get a lot of liquid on your cutting surface," says Casatelli. "It means you're not cutting the tomato—you're squishing the tomato." If that starts to happen when using your serrated knife, it's time to sharpen.

How to Sharpen a Serrated Knife

Unfortunately, there isn't a simple at-home knife sharpener or a gizmo you can use to sharpen a serrated knife, which is trickier to sharpen than most other kitchen knives since the cutting side is jagged, not straight. While you can use a diamond or ceramic stone to freshen up most knives, even one of the best knife sharpeners won't bring your serrated knife back to life, says Casatelli.

Mail-In Services

Some knife makers, such as Zwilling, offer a mail-in sharpening service. Other knife makers may say that their knives never need to be sharpened—this means you're intended to throw it away once it dulls, rather than sharpen it.

The Process

To sharpen a serrated knife, only one half—the flat side, not the serrated side—is sharpened. Doing so calls for a computerized piece of equipment such as a Tormek, a Swedish-made sharpening tool with a grindstone and a leather honing wheel. The majority of the work involves a process called deburring, not grinding or sharpening.

1. First, the grindstone is used to raise the burr from the flat edge inside the serrations. A burr is a little curved bit of metal that pops up on the opposite side when you're sharpening one side of a knife blade. It indicates that you've sharpened that side of the blade enough.
2. Then, the burr is carefully taken off the serrated edge using the leather honing wheel.
3. Finally, the flat edge is polished.

To see a professional sharpen a serrated knife, watch this video from Knife Grinders Australia. The step-by-step clip goes into great detail; Casatelli says it's exactly how he works in his shop. Very dull serrated knives can take nearly an hour to sharpen, he says.

How to Maintain a Serrated Knife

Since you technically can't sharpen a serrated knife at home, it's important to handle it with care to keep it in optimal condition.

Storage

Don't throw your serrated knife into a drawer with other utensils, which might ding or scratch it as they knock around together. Instead, store it in a wood block or on a magnetic strip.

Use

When working with a serrated knife, always cut on a wood or hard plastic cutting board rather than directly on your countertop, especially if it's a very hard material like granite. Don't use it to chop or pry apart frozen food, such as rock-hard burger patties.

Cleaning

Finally, don't put a serrated knife in the dishwasher. The extreme heat can damage the handle's material—and other items can bump into it and ding the blade edge. "I have a microscope that blows up the handle and edge 100 times," says Cassatelli. "I can always tell when someone has put a knife in the dishwasher because the handle has shrunk. I can see all the little nicks and dings, too. If you watch chefs on TV or on YouTube, they always wipe their knives and put them away." He recommends treating your serrated knife with the same consideration.