The Best Electric Knife Sharpeners

Our top-rated sharpener had the winning combination of producing truly exceptional and consistent results quickly, neatly, and efficiently. The manual clearly outlined a few specific steps that must be followed each time, and it took about 2 minutes from start to finish to get a polished, razor-sharp edge. Narrow, spring-loaded slots made it easy and unambiguous to maintain a consistent angle as we moved the knife through the three slots. It rapidly removed a notch we cut in the blade and easily sharpened both our everyday chef’s knife and pricey carbon-steel chef’s knife. We subtracted half a point because the slots left very light cosmetic scratches along the sides of our knives.

This slightly simplified, more compact version of our top-rated sharpener has one fewer sharpening slot, with the same medium-abrasive diamond abrasive of our winner for shaping, and a flexible stropping disk to polish the edge. As a result, this sharpener created an edge with two reinforcing bevels, as opposed to the three created by the top-rated Trizor model. We noticed only a minor difference in cutting performances between the knife we sharpened in this model and the knife we sharpened in the Trizor, but knives sharpened in this model may require slightly more frequent sharpening to maintain their edges. Like the Trizor, the spring-loaded guides left light cosmetic scratches along the side of our blades.

This compact sharpener offers the advantage of being supereasy to use, at least in theory: You simply push a button to start a 90-second sharpening cycle. The speed of the rotating abrasive belt changes over the course of the cycle to shape, refine, and polish the edge of the blade as you pass the knife through a single set of left and right slots. While the results could be superlative, with excellent results in our sharpness tests, we didn’t find that they were consistently so. It’s up to the user to hold the knife in the correct position in the slots, which don’t grip the knife or guide the blade’s angle against the abrasive belt. We’d often reach the end of sharpening to find that a spot along the knife wasn’t quite as sharp as the rest of the blade; we usually had to repeat cycles. Removing the notch took twice as long as it did with our winner, but it eventually worked very well. The included 10-inch ceramic honing rod was a great addition for polishing up the edge after a sharpening cycle or for light maintenance of your knife between sharpening sessions. One disadvantage: The abrasive belt cut into the Fibrox handle of our chef’s knife, leaving it rough and slightly damaged where it joins the blade.

Named for a famous knife maker, this little powerhouse of a machine got dazzling sharpening results but made a mess of our countertop with metal filings and chewed off the edge of our knife handle before we even noticed. Its exposed rotating belts (and extensive, complicated instructions) can be daunting, but if you are up for handling a semi-industrial tool, this is a great device, with five professional-grade abrasive belts and the ability to customize the angle and speed of sharpening for everything from kitchen knives to hunting blades to tools.

This “professional” model from Presto offers three stages of coarse to fine sharpening using Sapphirite, a synthetic ceramic. This model also offers a blade selector that lets you set the sharpening angle (thick, medium, or thin); however, the company did not tell us what angle or angles it creates. Diagrams on the machine indicated that we should use the “medium” setting when sharpening a chef’s knife, but we got somewhat better results using the “thin” setting. Still, that’s not saying a lot: Our sharpening results were inconsistent, with wildly varying sharpness scores after each cycle—some not bad, others very poor—and they varied when we checked sharpness at different points along the blade. The edge looked almost microserrated after sharpening. The heel of the knife got a deep indentation by the end of testing, and the notch never fully disappeared. Sparks flew when we sharpened the carbon-steel blade; while the manual warned that this could happen, it was shocking to see, though it eventually did an acceptable job sharpening that blade.

While this simple sharpener with two stages isn’t difficult to use, it makes a lot of noise and never restored the sharpness of our everyday chef’s knife, leaving the edge toothed and roughened. The company did not tell us what angle this machine was sharpening blades to, but that scarcely mattered considering the results we got. After sharpening, the knife no longer glided through paper, and the industrial sharpness tester gave its edge a bad score, which only got worse as we repeated the sharpening cycle. The heel of the blade was worn down after testing, and we never could fully repair the notch damage. Instead, as we worked on it, the blade became hot while the abrasive ground a half-inch-long, gradual indentation in the blade edge where the notch had been. We were disconcerted to see sparks as we sharpened the carbon-steel blade on the Sapphirite abrasive, though the manual mentioned this was possible. That knife’s final sharpness score was unacceptably bad.

This handsome, single slot, block-like sharpener had a great premise: You dial up the angle you want and simply pass the knife through a single slot until it is sharp. Alas, it was too good to be true: The dial tended to drift as the powered-up machine vibrated, changing the sharpening angle. The abrasive failed to make much of a difference with our dull knives, leaving us running the blades through the slot over and over, our hopes diminishing. The sharpness scores veered up and down the scale but never got steadily better. We gave up on trying to repair the notch, and the carbon-steel blade fared no better than our everyday knife; in fact, its sharpness scores got worse and worse the more we tried. The cutting edge on both knives looked rough and toothed by the end of testing.