The tool commonly referred to as a sharpening steel—it looks like a lightsaber—should really be called a honing steel. Norman Weinstein, a chef-instructor of knife skills at the Institute of Culinary Education in New York and the author of Mastering Knife Skills, says that a steel will probably last about three to four years. “If you run your thumbnail around the perimeter, you’ll feel the grooves; if you can’t feel them, they’ve worn down.” At that point, it’s time for a new one.
You should hone your knives every time you use them. If you looked at a knife under a microscope, Weinstein says, it would look like a bunch of teeth pointing out. As the blade is used, those teeth fold down. A honing steel realigns the teeth so they point out again, enabling the knife to cut better. It’s important to note that regular honing steels won’t work with some super-hard-steel knives like the high-end Japanese Global knives.
You can use a diamond sharpening steel for touch-ups when your honing steel has stopped being effective. But Weinstein says that your knives should be professionally sharpened about once a year. Sharpening is the process of rebeveling the edge of a knife by putting it on an abrasive tool and actually grinding some of the steel off.
When buying a honing steel, look for one that’s two inches longer than your longest knife (for example, a 12-inch steel would be best for a 10-inch knife). Expect to pay between $55 and $75 for a quality medium steel. (The designation medium or regular refers to the spacing of the grooves around the steel, not the hardness.)
See Chowhound for more tips on sharpening knives.