How to Level a Sharpening Stone


by Sami P., 3.9.2024
Most users know that a sharpening stone needs to be leveled regularly, but many are surprised at how quickly the stone can wear down and develop a hollow. Even if you can't see the hollow with the naked eye, it's possible that after just 1-2 uses, the sharpening stone will have a depression that reduces contact with the knife, making sharpening ineffective. Naturally, the wear of the stone is influenced by the hardness of the stone, the sharpening technique, and what you are sharpening. 

Tasoituksentarvetta I often show customers this green Naniwa Pro 400 stone, which serves as a good example of what happens when you sharpen 5 kitchen knives and then start working on the sixth and realize that it's no longer progressing. The depression that has formed on the stone only becomes visible once you start leveling it.

In this blog, you'll learn how to level your sharpening stone effectively and what factors to consider when choosing a leveling stone. Using a leveling stone is an essential part of maintaining your sharpening stone, as it ensures a flat surface and improves sharpening results. You'll also get practical tips to ensure that your work is efficient and that your sharpening stone remains in good condition for a long time.

Does the sharpening stone need to be flat?

The answer is clear. If you know what you're doing and understand the challenges that a hollow caused by a knife can bring to sharpening, you can manage quite well without leveling. However, I would say that there is an area on the sharpening stone that should be flat. This is the area in the middle of the stone, extending about 6 centimeters in both directions, for a total of 12 centimeters on a standard-sized stone. This much flat surface is what you need for successful sharpening. In basic knife sharpening, it doesn't matter if some portion of the narrower end of the stone, for example, bends downward; these often occur when the stone is leveled incorrectly or when the leveling stone is warped.

How to choose the right leveling stone?

Choosing the right leveling stone is essential but by no means easy. A common misconception is that only the grit of the leveling stone determines the choice, but this is not the case. There are sharpening stones whose composition clogs most leveling stones, meaning only diamond stones work. Particularly challenging are the coarsest and hardest sharpening stones. A good example of a difficult stone to level is the Shapton Kuromaku 120.

Although diamond stones are convenient and effective leveling stones, it's not worth buying them solely for leveling purposes. Many customers have found that the Atoma 140 works well both as an effective leveling stone and as a coarse sharpening stone.

 
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The basic guideline for choosing a leveling stone is that if you have a so-called surface-slurry sharpening stone, it can be leveled with any coarser leveling stone. The challenge, however, is finding the right leveling stone for hard, so-called fully ceramic stones. One effective stone is the Naniwa PA Leveling Stone. This stone, which uses pink aluminum oxide, is just about effective enough for Shapton Glass and Rockstar stones.

Naniwa Flattening Stone PA #220
 
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A general tip is to level the sharpening stone before each use. This way, leveling is quick, easy, and effortless. If you leave leveling for long periods, you'll have to do a lot of work to get the stone flat again.

Techniques for using a leveling stone

When leveling, you can use both straight and circular motions, depending on what feels natural. Move the leveling stone evenly and symmetrically across the surface of the sharpening stone and avoid uneven movements. This ensures that the sharpening stone becomes flat and improves sharpening results.

I often say that leveling is successful when you move the leveling stone symmetrically asymmetrically. By this, I mean that by moving the stone equally in all directions and varying the direction, you achieve an even result.

One key aspect of leveling is pressure control. Use light but consistent pressure throughout the process. This prevents uneven wear on the leveling stone and the sharpening stone. I often notice that during leveling, pressure tends to concentrate at the beginning of the stroke, causing the sharpening stone to wear unevenly.

The movement of the leveling stone

The most important aspect of leveling is the correct movement. The style is free, but the biggest mistakes are made in how the leveling stone is placed on the sharpening stone. One of the most common mistakes is placing the leveling stone at a 45-degree angle on the sharpening stone so that both edges hang off the sides. This wears down the center of the leveling stone, turning the sharpening stone into a banana shape.

Correct the movement by having the leveling stone travel the longest distance from the bottom right corner to the top left corner, reaching the top right corner at the same time. After a few firm strokes, change direction.

This technique requires some practice, but it is essential for achieving a flat surface.

Checking the flatness of the sharpening stone

Checking the flatness of the sharpening stone is important to ensure effective sharpening. An uneven sharpening stone can lead to poor sharpening results and damage to tools. Therefore, it is important to check the flatness of the stone before and after leveling.
 
One common way to check flatness is to draw a grid on the surface of the sharpening stone with a pencil. Continue leveling until the grid has completely disappeared. This clearly shows where the stone is uneven and where it needs more grinding.

Maintaining the leveling stone

It's important to remember that the leveling stone also wears down, and depending on the leveling method, it can develop rounded edges or other irregularities. It’s a good idea to monitor the wear on the leveling stone; if you notice signs of irregularities, take a sheet of sandpaper (grit P40). Do not wet the stone, but gently and evenly rub the leveling stone on the sandpaper sheet. This way, you can easily remove the largest irregularities.

In summary

- Draw a grid on the surface of the sharpening stone to check for irregularities.

- Use light and even pressure during leveling.

- Ensure the sharpening stone is well-soaked before leveling.

- Check flatness after each use.

- Try different movements and paths to achieve a flatter surface.


The following video has a tip or two for leveling the sharpening stone and choosing the right stone.

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