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How can I best sharpen dull knives?

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I have some pretty common knives at home that I use for cutting vegetables, fish, meat and everything else that needs cutting. I don't have specific knives for specific kinds of food but rather use all knives for everything depending on what is quickly available.

Some the knives have become dull over time. I can still cut stuff with them but food that's a little bit more squishy like tomatoes can't be as precisely cut as before.

The knives were bought in a local supermarket and are just kitchen knives, nothing expensive or special.

How can I most effectively sharpen these knives? Does it even make sense to sharpen them again or should I just buy new ones? If I were to use a any additional equipment (whetstones, etc.), how do I best use them from a technical point of view (sharpening in a certain degree, etc.)?

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2 answers

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The Scary Sharp system is, in general, the cheapest reliable method of getting blades sharp. It consists of getting a solid, flat work surface, adhering abrasives (sandpaper, to begin with) to the surface, and working your blade over it with the cutting edge as flat as possible. By using progressively higher grits (harder, finer abrasives) a blade edge can easily be worked to a mirror polish.

Wikipedia has an article on it: https://en.wikipedia.org/wiki/Scary_sharp

Although there is a kit sold as Scary Sharp, it is entirely a manufacturer picking up an idea other people had.

As for the knives themselves: there are a lot of terrible knife-shaped objects out there, but also a lot of reasonably-priced good knives, and of course a large number of expensive knives -- which might be good or bad. While you can assume that the very cheapest knives are not high-quality, above that level quality is not directly associated with price.

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Is this specific to straight edges, or is there a way to apply it to serrated ones too? Monica Cellio 13 days ago

TL;DR: you need one or more round rods coated in abrasive to handle serrations. Scary Sharp works best on flat edges and reasonably well on gently curved edges -- in the cooking world, best on slicers, very well on chef's knives, and less well on highly curved paring blades. [1700 characters on pros and cons of serrations omitted.] dsr 9 days ago

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On serrations:

Serrated edges are a mixed blessing. They accomplish several purposes:

  • serrations pack more cutting edge length into the same overall blade length. This gives a mechanical advantage to your cut.

  • serrations protect the inner curves of each scallop from being banged around. This keeps them sharper.

  • serrations offer extra points, so the cutting action can dig in repeatedly across a stroke.

Those are all pretty positive. Now the negatives:

  • First, it's really aggravating to sharpen. (Here's the answer to "how do you sharpen a serrated blade?") A typical serration is either one scallop repeated or a repeating pattern of small and large scallops. There's another mechanized "micro-serration" method which effectively files rows across the blade, ending in small points. For each of these, you need to get an abrasive rod with a diameter approximating the diameter of the scallop, and then rub that up and down in the scallop, maintaining an angle with the blade that matches what you want. Assuming that there are no serrations on the reverse side of the blade, you can use Scary Sharp methods there - but it will be less effective, and very good at reducing the serration depth by wearing away the points.

There are typically so many micro-serrations that you will not be able to muster the patience or dexterity to get them all. Luckily, such knives are generally very cheap.

  • Serrations are great on bread and tomatoes, but terrible for precision cutting.

Most bread knives are serrated. If you keep your chef's knife or utility knife well-sharpened, and use correct cutting technique, you won't need a serrated knife for tomatoes.

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