Sharpening

Sharpening is the process of creating or refining a sharp edge of appropriate shape on a tool or implement designed for cutting. Sharpening is done by removing material from the implement with an abrasive substance harder than the material of the implement, followed sometimes by processes to polish the sharp surface to increase smoothness and correct small mechanical deformations without removing significant metal.

The process creates a bevel - the angled surface that meets at the cutting edge. Ideally, the two sides of the edge meet at a precise mathematical point (the apex), though in practice, a microscopic radius always remains. Sharpening is distinct from honing or steeling, which are maintenance steps used to realign an edge that has rolled over during use, though the terms are often used interchangeably in casual conversation.

Tools and materials

Sharpening generally involves the use of an abrasive material that is harder than the tool steel being sharpened. The hardness of sharpening materials is often measured on the Mohs scale. Tools can be categorized by their method of operation: abrasive stones, mechanical grinders, and honing devices.

Abrasive stones

Also known as whetstones, these are blocks of abrasive material used for manual sharpening. They require a lubricant—typically oil or water—to reduce friction and flush away swarf (metal filings) to prevent the stone's pores from clogging.