How to Sharpen a Serrated Knife
Oct 16, 2023
A serrated knife, also called a bread knife, is one of the most underrated and versatile tools in your kitchen.
Elyse is a former senior editor for Martha Stewart Living.
A good serrated knife is essential. It might be even more useful than your chef's or paring knife. It stays sharper longer than your other knives (since less of its blade hits your cutting board), and its jagged edge allows it to slice as effortlessly through produce and crusty baguettes alike. But, like your other kitchen tools, a serrated knife can become dull over time. Sharpening it, however, might seem less straightforward, due to its ridged blade.
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.
Most serrated knives measure between 4 1/2 to 10 inches long, but some serrated knives for cutting cakes measure around 18 inches.
The best serrated knives are made from German or Japanese steel, which is higher quality than Chinese steel, says Enrico Cassatelli, the owner of Knife Sharpening of Bergen County in Paramus, N.J. 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 one than it is sharpen them up.
By comparison, a quality serrated knife made from Japanese or German steel can cost as little as $50—and can be sharpened repeatedly.
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 prime candidates for cutting with a bread knife, since it can "bite" through the skin.
The specific timing depends on how often you use your serrated knife and how well you maintain it. Regardless, you'll know it's time to sharpen your serrated knife when it stops working well. "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 Cassatelli. "It means you're not cutting the tomato—you're squishing the tomato."
If this happens, know that you haven't done anything wrong. After all, knives are meant to be used, and when you use them, they get dull. "Dulling a knife is a function of using the knife," Cassatelli says. As you cut and the knife blade hits the cutting board, it dulls a bit, especially if you don't ease up as you hit the board. "Most people don't relax the pressure as they get close to the board," he says. "That's why with any knife, the third of the blade closest to the tip is always the dullest part. Most people push down hard to make the final cut."
Unfortunately, there isn't a simple at-home knife sharpener or a gizmo you can use to sharpen a serrated knife, which are 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, Cassatelli says.
Some knife makers, such as Zwilling, offer a mail-in sharpening service. It costs $89 to send in four knives to be sharpened. Other knife makers may say that their knives never need to be sharpened— what this means is that you're intended to throw it away once it dulls, rather than sharpen it.
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.
To see a professional sharpen a serrated knife, watch this video from Knife Grinders Australia. The step-by-step clip goes into great detail; Cassatelli says it's exactly how he works in his shop. Very dull serrated knives can take nearly an hour to sharpen, he explains.
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.
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.
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.
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.