When sharpening a tool on a grindstone, why is the tool often dipped in water?

Dipping a tool in water while sharpening it on a grindstone primarily serves to prevent overheating of the tool. When metal tools are sharpened, they can generate significant heat due to the friction created by the grinding process. Excessive heat can lead to several negative outcomes, such as losing the temper of the steel, which reduces the tool's hardness and effectiveness. By regularly dipping the tool in water, the temperature is controlled, ensuring the integrity of the metal is maintained and that the tool retains its sharpness for longer periods.

Other options, while they might seem relevant, do not capture the primary reason for this practice. For instance, while the process might have some minor cleaning effect, that is not its main purpose. Additionally, lubrication is typically not necessary when using a grindstone, and improving the sharpening process is not fundamentally reliant on the water; rather, it is a safety and maintenance measure for the tool itself.