Abrasive stone

Sharpening stones Sharpening stone is a general name given to any stone natural or artificial to be used by hand. Manufactured abrasive stones are made by the same methods employed in grinding wheel production. The finished stones as they come from the vitrifying kilns are rubbed on circular cast iron revolving beds to smooth their surfaces (Jacobs 1928)... 

Honing is an abrasive machining process that produces a precision surface on a metal workpiece by scrubbing an abrasive stone (grain) against it along a controlled path. 

A superfinishing abrasive stone is generally vitrified bonded and has a hardness range of HRH20-70. White aluminum oxide, silicon carbide, cubic boron nitride, or diamond abrasive is used. Abrasive sizes in the JIS 300- 500 range are used for coarse finishing, while JIS 600- 1500 abrasives are used for a fine finish (Matsui and Nakasato 1965, Onchi et al. 1995, Varghese et al. 1998). 

Roll crushers are used for less abrasive stones than cone crushers. They are most effective on soft and friable stones, or when a close-sized product is required. 

The removal of small amounts of material by floating segmented abrasive stones mounted on an expanding mandrel, which rotates with low rotary speed and reciprocates along the surface of the workpiece (see 4.8F). 

Sandstone. Sandstone wheels were once quarried extensively for farm and industrial use, and special grades of stone for precision honing, sharpening, and lapping are a small but important portion of today s abrasive industry. Production of honing and sharpening stones from deposits of dense, fine grain sandstone in Arkansas account for 76% of the value (about 2 million in 1987) and 88% of the total quantity of such stones in the United States (4). 

Deteriora.tlon. An important source of damage to stone objects is mechanical in nature. Both breakage and abrasion account for much of the losses on objects made of this relatively fragile material. More difficulties are offered by the processes of a chemical nature which play a role in stone deterioration (132—134). 

Includes abrasives, paper manufacture, and refractory stone (including ganister). 

Pulpstones. Improvements have been made in the composition and speed of the grinding wheel, in methods of feeding the wood and pressing it against the stone, in control of power to the stones, and in the size and capacity of the units. The first pulpstones were manufactured from quarried sandstone, but have been replaced by carbide and alumina embedded in a softer ceramic matrix, in which the harder grit particles project from the surface of the wheel (see Abrasives). The abrasive segments ate made up of three basic manufactured abrasive siUcon carbide, aluminum oxide, or a modified aluminum oxide. Synthetic stones have the mechanical strength to operate at peripheral surface speeds of about 1200—1400 m /min (3900 to 4600 ft/min) under conditions that consume 0.37—3.7 MJ/s (500—5000 hp) pet stone. 

Type III dental stones are used for casts requiring higher compressive strength and abrasion resistance than casts formed using the type II plaster. These dental casts are used for the processing of denture-base materials. 

Enzymatic desizing is one of the oldest nonfood appHcations of commercial amylases. Another type of enzyme, microbial ceUulases, has developed within the textile iadustry as a tool for fabric finishing, ia particular for denim garment finishing. CeUulases can achieve the fashionable worn look traditionaUy obtained by the abrasive action of pumice stones, ie, stone-washing. 

Stone-washing is carried out by lightweight pumice stones that are put into industrial laundry machines with the jeans. The stones mb against the denim and remove some of the dye. However, too much abrasion from stones can damage the fabric, particularly hems and waistbands. 

The tables given under this subject are reprinted by permission from the Smithsonian Tables. For more detadea data on thermal expansion, see International Critical Tables tabular index, vol. 3, p. 1 abrasives, vol. 2, p. 87 alloys, vol. 2, p. 463 building stones, vol. 2, p. 54 carbons, vol. 2, p. 303 elements, vol. 1, p. 102 enamels, vol. 2, p. 115 glass, vol. 

Metal to metal Metal to stone Rotary impact Abrasive wheel Buffing disc Tools, drill Boot studs Bearings... 

Abrasion under limited slip used to be, and to some extent still is, measured either with the standard Akron abrader or the Lamboum abrader. In case of the Akron abrader the sample runs under a slip angle at a constant load against the abrasive surface of an alumina grind stone. Speed and load are fixed the side force is not measured. 

Cutting, grinding, and shaping stone, and in particular burnishing and polishing the surface of stone as well as metals, requires the use of abrasive materials that are harder than the solids to be cut, ground, burnished, or polished. Sapphire and ruby, two very hard gemstones, for example, can be cut or polished only with the assistance of diamond powder, an abrasive that is harder than sapphire or ruby. Diamond is the hardest material... 

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