Sharpening

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For image sharpening, see unsharp masking.

A hand-cranked knife sharpener in Chennai.

Sharpening is the process of creating or refining a sharp edge on a tool or implement. The term has a wide application but can be expressed as the creation of two intersecting planes which produce an edge that is sharp enough to cut through the target material. For example, the blade of a steel knife is ground to a bevel so that the two sides of the blade meet. This edge is then refined by honing until the blade is capable of cutting.

The extent to which this honing takes place depends upon the intended use of the tool or implement. For some applications, a certain amount of jaggedness about the edge is acceptable, or even desirable, as this creates a serrated cutting edge. In other applications, the edge must be as smooth as possible.

In general, sharpening can be divided into two phases. First the edge is sharpened with an abrasive sharpening stone which shapes the blade primarily by removing material. Second, the edge is honed, or steeled, Steeling is done by passing the blade against nearly-smooth hard metal steel which plasticly deforms the material of the blade's edge, smoothing out rough edges. Honing, or stropping, may also be done by polishing the edge with a fine abrasive such as rouge or tripoli on a piece of stout leather.