It really depends on how much you use them and how much abuse they take, but knives generally need sharpening once or twice a year. If a knife feels dull or has trouble cutting, sharpen it. Just note that every time you sharpen a knife, it removes a little bit of metal. After many repetitions, there won't be enough left to sharpen, and it'll be time to replace your knife. We choose the most popular manual and electric knife sharpeners available at UK retailers to test. We buy all the products we test and rate them on the two factors below. Sharpening ability Sharpening a knife blade removes tiny bits of metal, and those will need to be removed from the sharpener once in a while. Many models have a compartment in the bottom to collect metal filings, which you can simply dump into the trash and wipe clean with a wet cloth. (If there's no compartment, turn the unit over and lightly tap to get the filings out.) You can also clean the abrasive parts with a cloth or a soft brush dampened with water; make sure to let everything dry completely before using again. Unless the directions say otherwise, it's not a good idea to use soap or any kind of oil to clean a knife sharpener, as you can damage the abrasive. Keep knives in a covered, safe environment when not in use," says Hartley. "Do a weekly light hone with steel or stone, always wiping away particles with a clean dry towel. Don't feel like you have to work fast—with a process like this, form is everything. Work out the proper form first, and then the speed will come." Can you sharpen kitchen shears with a knife sharpener? Carrie Honaker, who updated this roundup, is a food writer who has wielded many knives over the years. As a restaurateur and avid home cook, she knows the importance of caring for your knives to maintain steady, sharp edges. Her work has appeared in many publications, including Bon Appetit, Allrecipes, and Wine Enthusiast.

To discover the best knife sharpeners on the market, we collected an array of dull knives—plus several boxes of Band-Aids—and tested their performance slicing through paper, carrots, and tomatoes (and a baguette, for serrated blades), both before and after sharpening. We also measured each knife's sharpness scientifically, using an Edge-on-Up tool to record the exact amount of force needed to cut through a standard material. Pull the knife blade along the sharpening steel towards you, with enough gentle force that you can hear a grinding noise. A whetstone combined with a honing steel gives the best results (better than knife sharpeners). But (and it's a big but) only use this method if you know what you're doing. Otherwise, you risk damaging the cutting edge of your knife.

Global Knives

How well the sharpened knives performed: We examined their ability to slice through paper, tomatoes, and carrots both before and after sharpening. For models that claim to accommodate serrated knives, we tested their slicing performance using a baguette. We rate each knife sharpener on how easy it is to set up and use, plus how easy the instructions are to follow. Things we learnt testing knife sharpeners This process is essentially the same with both a manual and electric sharpener, but the motorized abrasives in an electric model will do more of the work for you. The most important thing is to try to use the same amount of pressure and the same angle with each pull through the slot—different models of sharpener make this easier or harder, depending on their design. Unless the directions specify otherwise, it should take three to five pulls through the coarse slot, and then just a couple through each finer slot, to sharpen the knife. If it's not as sharp as you like, try a few more pulls through the finest grit slot, and if that doesn't work, try the whole process over again. When the sharpener has more than one setting, the coarse setting is the sharpener and the fine one is normally similar to a honing steel. All that’s left to do is dig out your blunt and damaged Global Knives and get them sent off to us to get them sharper than new!

A honing steel is a long rod, often included in knife sets, along which you run both sides of the blade before you start slicing and dicing. It helps maintain the integrity of the blade, straightening out some of the microscopically uneven spots on the edge without actually removing any metal. Used regularly—as in every few times you use the knife—it can help stave off dullness, but you'll still need to sharpen your knife on occasion. Finish with a honing steel for best results. Rinse and dry the knife. You may also need to clean up the area around the whetstone.

We love Global Knives as the quality of the steel (CROMOVA 18) is fantastic. The steel has the great property of being hard but malleable and sharpens up really well to create a razor-sharp edge. As we work on Global Knives so often, we have sharpened and repaired pretty much every model and type of Global Knife including the Classic, Ni, UKON, and Sai ranges as well as the limited-edition models they produce. We can safely say our Global knife sharpening service is the best and most comprehensive in the UK. Rebecca Treon, who also updated this piece, is a food writer, experienced home cook, and mother of two. Her work has been featured in BBC Travel, Huffington Post, Hemispheres, and Thrillist. Handheld manual knife sharpeners are designed to keep your blade fresh, and you should use them to top up the blade after every few hours of use. An electric knife sharpener or whetstone would be your best bet for a fully dulled knife. Jason Horn, a commerce writer for The Spruce Eats, updated this roundup to include data from our extensive tests of 22 sharpeners—10 electric and 12 manual—by both freelance testers and in our Lab in Birmingham, Alabama.