How to Sharpen a Serrated Knife

Serrated knives are a kitchen marvel. They breeze through tricky tasks like slicing tomatoes, crusty breads, and tender cakes without squashing, smushing or otherwise destroying them. If you've ever tried to use an ordinary chef's knife to do one of these things, you know how frustrating that can be.

But if that weren't enough to qualify serrated knives as one of the great wonders of the culinary world, consider that they rarely—if ever—need sharpening.

How Do Knives Go Dull?

Knives don't get dull because of the foods they're cutting, but rather, the cutting board. (This assumes ordinary use—not the kinds of abuse that so many kitchen knives are known to endure, like being sent through the dishwasher, tossed into a drawer, or used for opening cans.)

Every time you slice something on a cutting board, the edge of a knife blade is going to suffer. First, it can be knocked out of true: the sharp edge is still there, but it's been bent over backwards. This is easily remedied by a few strokes on a honing steel. 

Worse is when, after a long time of striking the cutting board, the sharp edge has been worn down, so that what once looked like a V now looks like a U. In this case, you need to grind away a bit of metal to reshape that dull edge back into a sharp one. And the way that's normally done is using a sharpening stone. 

Serrated Knives Stay Sharp

However, because the sharp edges of a serrated knife are recessed, they don't actually touch the cutting board. Which means a quality serrated knife can stay sharp for a very long time—as in years. 

Even so, you might eventually find that your serrated knife is not performing with the ease with which it once did. One sign of this is that it leaves crumbs on the cutting board when slicing bread, whereas it used to slice cleanly through.

If that day comes, you have options:

• Check your manufacturer's warranty. Many knife manufacturers will sharpen your knives, including serrated knives, for free. You just have to send it back to them. 
• Take it to a professional knife sharpener. Some places will say they don't do serrated knives, but plenty of places will.
• Do it yourself. 

Sharpening a Serrated Knife

If you're familiar with how to sharpen an ordinary chef's knife, you know that it involves applying a series of long strokes on a sharpening stone, then reversing it and doing the same to the other side of the blade.

This is fine for a straight edged knife, but serrated knives are totally different and they need to be sharpened differently.

If you look closely at the edge of a serrated knife, you'll see that it consists of a series of individual curved serrations. You'll also notice that one side of the blade is beveled (meaning it has indentations in it) whereas the other side is flat. 

So when sharpening a serrated knife, you need to sharpen each one of these beveled serrations separately, one at a time. And you won't be sharpening the flat side of the blade at all.

Fortunately, there's a special tool designed to let you do just that. It's called a sharpening rod.

How to Use a Sharpening Rod

A sharpening rod (like this one) is rather like a honing steel, except it's smaller and narrower, and it tapers to a point, which means it offers various thicknesses along the shaft of the rod. This is helpful because the serrations on different knives are different widths and you want to apply the section of rod that best fits the serrations of your knife. Sharpening rods are available in steel, ceramic, and even diamond.

With the section of rod fitted to the serrations, simply drag the rod across those serrations. Keep the rod flush with the bevel and you'll have the right angle. It doesn't matter which way you drag the rod, but for safety's sake, drag it away from the blade, so that you won't accidentally slip and cut yourself.

Give each serration four or five strokes before moving on to the next one. As you can see, if your knife has 30 or more serrations, this is going to take a little while. But it's an easy enough process. 

When you're done, flip the knife over and give the flat side of the blade a few strokes on a regular sharpening stone, or even a piece of fine-grit sandpaper. This is to smooth out the burr that you've raised on the edge of the knife. Finally, wash and dry the knife as usual and you're all done!

Sharpening Cheap Knives

Note that some manufacturers claim that their serrated knives never need sharpening and in a sense, they're right. But not because the blades are so invincible that they literally stay sharp forever, which if you think about it is a physical impossibility. 

No, what that claim really means is that the knife is so cheap that when it goes dull, you should just throw it away. You'll usually be able to identify these knives as much by their price tags as by the flimsy feel of the blades: they feel like you could bend them in half with your hands. Knives like this are really not worth the trouble of sharpening, certainly not one bevel at a time. 

But in a pinch (as in, as a last resort before throwing it away) you can give the back (i.e. the flat) side of the knife a single pass on a regular sharpening stone, then wash and wipe it dry. But ultimately, as with most kitchen tools, a high quality serrated knife will last longer and serve you better.