Sharpening stones are used to sharpen edges and hone internal or external surfaces. Generally, they are stones or bonded abrasive products with a rectangular, block, or shaped stick configuration. There are many types of sharpening stones. Abrasive files are bonded abrasive blocks for hand filing applications. Rubbing bricks are coarse, serrated stone blocks that are used for surface cleaning, reconditioning, and grinding wheel dressing. Bench stones are flat, rectangular stones for sharpening tools on a bench. Hones are designed for offhand honing of ground-cutting tool edges. Slips and slip stones are designed for honing the inner radius of a cutting tool, chisel, or gouge. Honing sticks and honing tools are used to finish internal bores. Special honing tools configurations are available for honing cylindrical surfaces and other specialized shapes. 

Abrasive Grains

Sharpening stones use several different types of abrasive grains. Examples include aluminum oxide, silicon carbide, super-abrasive diamond, and cubic boron nitride. Aluminum oxide, the most common mineral in use today, is used either individually or with other materials to form ceramic grains. Titanium and chromium oxides are also used as additives. Silicon carbide is harder than aluminum oxide, but more friable. Super-abrasive diamond pastes are useful in ferrous polishing or lapping applications where heat and reactivity are not a factor. Cubic boron nitride (CBN) is a superabrasive grain with hardness second to diamond and a cubic crystal structure. Other types of abrasive grains include Arkansas stone, India stone, and water stone. Sharpeners and sharpening stones that consist of several different stone types or grades are also available. 

Grit Sizes and Bond Types

Sharpening stones differ in terms of grit sizes and bond types. Grit sizes are based on ANSI (U.S.), FEPA (European), JIS (Japanese), and Micron graded standards and describe both upper and lower limits. Bond types include resin, plastic, rubber, shellac, silicate or oxychloride, and vitrified glass. Metal bond systems are used mainly for superabrasive or tungsten carbide grit products. There are three basic types of metal bonds: sintered, metal single layer, and electroplated. Sintered metal bond systems are used when a thicker layer of superabrasive is required. Metal single layer (MSL) wheels consists of a specialized braze layer that forms a single layer of superabrasive. Electroplated bonds are used to produce fine grit superabrasives. 

Degrees of Coarseness

There are four degrees of coarseness for sharpening stones. Coarse or extra course products are designed to provide rough or initial sharpening of the cutting edges of knives, blades, or other cutting tools. Products with medium coarseness are well-suited for deburring, the removal of sharp edges from machining, casting, or other manufacturing processes. Sharpening stones with fine coarseness are used for stoning or intermediate finishing between medium sharpening and final honing. Extra fine, very fine, and ultrafine products are suitable for imparting the proper finish to part surfaces. Honing, lapping, super finishing and polishing are common finishing techniques. Other uses for sharpening stones include the finishing of precision shafts, connecting rods, and internal diameters. 


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