Many customers say so, but it does not mean that the simple kitchen knife sharpener becomes useless. Even NHK (Japan Broadcasting Corp.) has shown a program on this and said that kitchen knives are sharper when the edge of the blade is like a saw, which has led to the misunderstanding that leaving the knife sharpened with a rough grindstone is better for sharpness. However, the fact is that the sharpening stones are not used by hand.

However, even if you manually sharpen a kitchen knife horizontally using a whetstone, it will still cut. A simple kitchen knife sharpener is a temporary measure to easily restore the sharpness of a kitchen knife, so the angle of the built-in coarse whetstone is quite obtuse and is designed to sharpen only the cutting edge of a kitchen knife.
Therefore, the edge of a kitchen knife becomes thicker after repeated use.

Therefore, you can use a simple kitchen knife sharpener, but it is better to use a whetstone once in a while to reduce the thickness of the kitchen knife’s edge.
However, please use a whetstone once in a while to reduce the thickness of the edge of the blade.

If you have been using a simple kitchen knife sharpener for a long time, we recommend that you ask a reliable kitchen knife sharpening specialist (an endangered species) to sharpen your kitchen knives because the work is time-consuming.

After that, the simple knife sharpener will work well again.

Incidentally, the basic fee for sharpening household knives at our store is 1,000 yen, and we are inundated with requests for sharpening from all over the country, so we require three days for the work to be completed. If you are in a hurry, we offer a speedy service that takes about one hour.

*This is a translation by a translation tool.