Sharpening stone

(Grit size is given as a number, which indicates the spatial density of the particles; a higher number denotes a higher density and therefore smaller particles, which give a finer finish to the surface of the sharpened object.)

The verb nowadays to describe the process of using a sharpening stone for a knife is simply to sharpen, but the older term to whet is still sometimes used, though so rare in this sense that it is no longer mentioned in, for example, the Oxford Living Dictionaries.

Novaculite is very hard and has small crystals (3-5 microns), making it suitable for the later fine stages of knife sharpening.

[8] One of the most well-regarded natural whetstones is the yellow-gray "Belgian Coticule", which has been legendary for the edge it can give to blades since Roman times, and has been quarried for centuries from the Ardennes.

The slightly coarser and more plentiful "Belgian Blue" whetstone is found naturally with the yellow coticule in adjacent strata; hence two-sided whetstones are available, with a naturally occurring seam between the yellow and blue layers.

[9] The hard stone of Charnwood Forest in northwest Leicestershire, England, has been quarried for centuries,[10] and was a source of whetstones and quern-stones.

Some shapes are designed for specific purposes such as sharpening scythes, drills or serrations.

For example, the proportional content of abrasive particles as opposed to base or "binder" materials can be controlled to make the stone cut faster or more slowly, as desired.

Belgium currently has only a single mine that is still quarrying Coticules and their Belgian Blue Whetstone counterparts.

The geology of Japan provided a type of stone which consists of fine silicate particles in a clay matrix, somewhat softer than novaculite.

[16] Besides this clay mineral, some sedimentary rock was used by the Japanese for whetstones, the most famous being typically mined in the Narutaki District just north of Kyoto along the Hon-kuchi Naori stratum.

Diamond plates can serve many purposes including sharpening steel tools, and for maintaining the flatness of man-made waterstones, which can become grooved or hollowed in use.

Truing (flattening a stone whose shape has been changed as it wears away) is widely considered essential to the sharpening process but some hand sharpening techniques utilise the high points of a non-true stone.

These diamonds are bonded onto a precision ground surface, set in nickel, and electroplated.

Here are some typical sharpening stone grit sizes and their uses when sharpening steel knives: Standards for grit size measurements include JIS, CAMI, ANSI, FEPA-P (for sandpaper), FEPA-F (for metal abrasives), and various trademarked standards for individual company product ranges.