What are knife sharpeners used for?

Knife sharpeners are used to restore a sharp cutting edge to knives that have become dull, by grinding or abrading the blade to create a new, keen edge. Knives inevitably lose their sharpness with use as the edge wears and dulls, and a sharpener removes a little metal to reshape and refine the edge back to sharp. They are used to keep your kitchen knives (and other knives) cutting well, because a sharp knife slices easily, cleanly and precisely, while a dull knife is hard work, crushes and tears food, and is actually more dangerous since it slips and needs more force. So the purpose of a knife sharpener is to maintain sharp, effective, safe knives by renewing their edge when it dulls. Our Best Knife Sharpeners compares five of them.

What knife sharpeners do

A knife sharpener is a tool or device that sharpens the edge of a knife by abrading it, using an abrasive surface, whetstone, abrasive wheels or slots, a diamond or ceramic surface, or an electric grinding mechanism, to grind away a small amount of metal from the blade’s edge and form a new, sharp cutting edge. Sharpeners come in several forms: whetstones (sharpening stones), pull-through manual sharpeners with slots, electric sharpeners, and sharpening rods or systems, but all do the same essential job of restoring the edge by removing metal.

So what a sharpener does is renew a dull edge into a sharp one. This is distinct from honing with a honing steel, which only realigns and straightens an existing edge between sharpenings without removing much metal; sharpening actually grinds a new edge when honing is no longer enough and the knife has genuinely dulled. Understanding that a sharpener abrades the blade to create a fresh sharp edge, restoring sharpness lost through use, explains exactly what it is used for, which is keeping knives sharp by resharpening them when they dull, the core of knife maintenance.

Keeping knives sharp

The core use of a knife sharpener is simply keeping your knives sharp, because knives dull with use and need resharpening periodically to stay effective. Every time you cut, the edge wears a little, and over time, even with honing, it becomes dull enough that it no longer cuts well, at which point sharpening restores the keen edge. So you use a sharpener to maintain your knives at their best, resharpening them when they have lost their sharpness, which for regularly used kitchen knives is a recurring maintenance task.

Keeping knives sharp matters because sharpness is what makes a knife do its job. A sharp knife cuts through food easily, cleanly and precisely, making food preparation quicker, nicer and more accurate, whereas a dull knife struggles, crushes and tears rather than slicing, and makes cutting hard work. So the sharpener is used to keep every knife, chef’s knife, paring knife, and others, performing properly by restoring the sharpness that use wears away, which is why it is a key part of looking after knives and why keen cooks keep and use a sharpener.

Why sharp knives matter: easier, cleaner, safer

A big reason knife sharpeners are used is that sharp knives are not just more effective but safer, which is often counterintuitive. A sharp knife cuts with little force and goes where you direct it, so you have control and the blade does the work, whereas a dull knife needs you to press harder and is prone to slipping off the food, and that slip, with force behind it, is how many kitchen knife injuries happen. So keeping knives sharp with a sharpener actually makes them safer to use, not more dangerous.

Sharp knives also give better results and are more pleasant to use: they slice cleanly without bruising or tearing food, make precise cuts possible, and turn chopping and slicing from a chore into an easy task, while a dull knife is frustrating and does a poorer job. So people use knife sharpeners to get all of these benefits, easier cutting, cleaner and more precise results, less effort, and crucially greater safety, by keeping their knives sharp. This is the practical payoff of sharpening and the real reason it is worth doing, which is what the sharpener is used to achieve.

Who uses them and the types

Knife sharpeners are used by anyone who owns and uses knives and wants them to stay sharp, which is essentially every cook, since all knives dull and need resharpening eventually. Home cooks use them to maintain their kitchen knives, keen cooks and those with good knives use them to keep their blades at their best, and anyone who notices their knives have become dull, hard to cut with, uses a sharpener to restore them. Some people sharpen their own knives, while others have knives professionally sharpened, but a sharpener is the tool for the job either way.

The type of sharpener used depends on the user and knives: pull-through sharpeners are quick and easy for everyday home use, electric sharpeners are fast and convenient, and whetstones give the most control and best results but need skill, suiting enthusiasts and fine or Japanese knives, while honing steels (used alongside sharpeners) realign the edge between sharpenings. So knife sharpeners are used across the board to maintain sharp knives, with the form chosen to match how much control, skill and convenience the user wants. In all cases, the use is the same: restoring and maintaining a sharp cutting edge so knives cut easily, cleanly and safely, which is what knife sharpeners are for.

The short answer

Knife sharpeners are used to restore a sharp cutting edge to dull knives by grinding or abrading the blade to form a new, keen edge, since knives inevitably lose their sharpness with use and need resharpening to stay effective. They come in forms like whetstones, pull-through manual sharpeners, electric sharpeners and sharpening systems, but all do the same job of removing a little metal to renew the edge, which is distinct from honing with a steel, which only realigns an existing edge. Their core use is keeping knives sharp by resharpening them when they dull, and this matters because a sharp knife cuts easily, cleanly and precisely, making food preparation quicker and better, while a dull knife crushes and tears, takes more effort, and is actually more dangerous because it slips. So sharpeners are used by essentially every cook to maintain sharp, effective, safe knives, with the type chosen for the control, skill and convenience wanted, all to achieve the same end of a sharp cutting edge.