whetstone

A whetstone is a stone used to sharpen blades by abrasion. The word whet derives from Old English, meaning to sharpen. Whetstones have been used for sharpening knives, chisels, and other edged tools for centuries across many cultures.

Common varieties include oil stones, water stones, diamond stones, and ceramic stones. Oil stones use oil as a lubricant; water stones use water; diamond stones fuse industrial diamonds to a plate; ceramic stones use hard, synthetic abrasive on a stable backing.

To sharpen, wet or oil the stone as required, set a comfortable edge angle, and move the blade across the surface with steady, even strokes, alternating sides. Coarser grits remove material; finer grits refine and polish. Whetstones can also be used for honing with very light pressure, depending on the grit and technique.

Regular maintenance includes cleaning away swarf, flattening the stone when it wears hollow (especially water stones), and storing it dry or in a protective case. Oil stones typically require a thin layer of oil on their surface between uses, while water stones are re-wetted as needed.

In addition to sharpening tools, the term whetstone may refer to places named Whetstone; this article focuses on the sharpening implement.