How to Use a Coarse Whetstone Without Damaging Your Knife

When sharpening a kitchen knife, we typically use three types of whetstones — coarse, medium, and finishing stones.
However, many people use them without fully understanding their characteristics and purposes.
Among them, the coarse stone requires the most caution: if used incorrectly, it can damage your knife instead of improving its sharpness.

A coarse stone generally refers to those with a grit rating below #400, such as #320, #220, or #120.
These stones have extremely strong cutting power, which makes them ideal for repairing chipped edges, correcting distortion, or thinning the blade.
On the other hand, they leave deep scratches on the blade and wear down quickly, which can cause the surface to become uneven.

Because of this, a coarse stone should not be used for the final edge sharpening.
Doing so is like putting a saw-like edge on a razor — the edge becomes rough and jagged, ultimately dulling the knife rather than improving it.

Many beginners make the mistake of using a coarse stone on a new knife, only to end up scratching or deforming the blade.
A coarse stone is a powerful tool, but it should be used only after you have mastered sharpening with a medium stone.
Think of it as a tool for shaping the blade, not for finishing it.

A coarse stone is for shaping, not for sharpness.
Used correctly, it can restore a damaged blade — but used carelessly, it can ruin one.