sharpening

thumb|A hand-held tungsten carbide knife sharpener, with a finger guard, can be used for sharpening plain and serrated edges on [[pocket knives and multi-tools.]]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.thumb|Video: Saw blade sharpening machine thumb|Edge/Apex of a knife after sharpening and stropping. Although this edge is sharp enough to bite a thumbnail, cut paper smoothly, or shave arm hair, the microscope plainly shows an edge which reflects light back into the lens. A truly sharp edge is too thin to reflect significant light. ==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.