Electric Knife Sharpeners

Even the most expensive, well-made knives lose their sharpness quickly when used regularly. And it doesn't take months, or even weeks: A knife can go dull in just a few minutes, especially if you're cutting through tough materials, such as bone.

What's the best way to maintain that snappy edge that makes light work of chopping and slicing? First, it's important to note that there's a difference between tuning up a relatively sharp knife and sharpening a dull knife. A so-called sharpening steel, the metal rod sold with most knife sets, doesn't sharpen at all: It's a tune-up device. As you cut with a sharp knife, the thin cutting edge of the blade can actually turn to the side, making your blade seem duller than it is. Running the knife blade over the steel, as most professional chefs do each time they're about to use a knife, simply realigns that edge and makes it straight again. It can't reshape a truly dull blade that's rounded and worn down. That's when you need a sharpener that can cut away metal and restore the standard 20-degree angle of each side of the edge.

To reshape the edge of a dull knife, you have a few choices, depending on the amount of effort, skill, and money you want to invest. You can send it out (inconvenient, even if you can find someone to do it). You can use a whetstone (very difficult for anyone but a professional). But the best option for most home cooks is to buy a tool (either electric or manual) that does most of the work for you.

Most sharpeners, both electric and manual, start their work with a coarse material and progress through stages of finer material to polish the edge. In general, the hardest material is diamond, followed by tungsten carbide, followed by high-alumina ceramic, followed by steel. Hardness isn't everything, though; the material is only as good as the angle of the knife being swiped against it, so the design of the sharpener is important. Some models guarantee that even an inexperienced user will get the right angle; other models make this more a matter of chance.

Most of the electric sharpeners we found to be up to the job. They did differ on how quick and easy they were to use. In addition to taking less time and trouble to reach a fine edge, newer models feature spring-loaded blade guides that allow no ambiguous wiggle room as they hold the blade against the sharpening wheels at the proper angle, replacing the trickier magnetic guides on older models. The sharpening wheels on newer models also reach closer to the edge of the machine, ensuring that the sharpening extends all the way to the end of a knife.

Should you bother buying a manual knife sharpener? The better options will help you maintain new knives and are fine with moderately dull blades. But be prepared to pay a professional to handle your more challenging sharpening needs. In the long run, an electric sharpener is a good investment, if you can make the initial cash outlay. If not, pick up a cheap manual sharpener. The best ones are far superior to steeling rods and will keep many of your knives in decent shape.