Serrated knife blades and gut hooks are sharpened differently than straight blades. Flat sharpening stones must not be used on them. You’ll need a specially-made, cone-shaped taper sharpener to get serrations. These often come with diamond layers, and they’re specifically designed to get inside each serration.
Picking your serrated knife sharpener
You’re going to need a tapered or cone-shaped sharpener for serrations. Push the sharpener toward the edge you wish to sharpen and work each serration individually. Be careful not to widen the serrations. Be sure, too to sharpen only one side of them (as the back provides support for the serrations). Note: Serrations are practically impossible to return to a pristine, factory-like state. If you do loose them, though, it’s not the end of your knife. Just sharpen the backside, and you’ve got a straight blade that will cut as well as any of your other straight knives. Another approach to sharpening serrations is to hold the rod sharpener still, place your thumb on the back of the knife, then slide your knife up and down against the sharpener. This can make it a bit more difficult to see exactly what you’re doing, but it’s markedly faster.
The trouble with serrations
Even with a special sharpener, it’s difficult to return the original edge to the serrations on your blade. Because of their construction, they’re more easily worn down than straight blades. There is one upside, though. Serrations work because they provide a sharp and varied surface against which things like rope can snag and more easily cut. That means, you don’t have to get your serrated edge perfect. It is, after all, the imperfections that make it so effective.
When to sharpen your serrated knife
Because of their unique construction, serrated knives are extremely difficult to sharpen, even with a taper sharpener. They’re prone to distortion and damage since they’re only cut into one side of the blade. Because they’re so easily damaged, it’s best to sharpen your serrated edges only when absolutely necessary — when you notice a dull spot for instance.
Using your taper sharpener
Place the point of the sharpener in the serration’s valley, and push the narrow end into the serration. Be careful not to push the taper too far, as you could widen the serration. Twist or rotate the taper while sharpening for a better result. With patience, your serrations will not grow wider, and they should get somewhere close to the sharpness they were when you purchased the knife.