ABRASIVES POWDER
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Written by tom
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Tuesday, 26 February 2008 |
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ABRASIVES is usually graded in sizes from 8 to 240 mesh. Coarse grain is to 24 mesh; fine grain is 150 to 240. Blasting abrasive for blast cleaning of metal castings is usually coarse grain. Arrowblast, of the Norton Co., is aluminum oxide with grain sizes 16 to 80 mesh. Grinding flour consists of extremely fine grains separated by flotation, usually in grain sizes from 280 to 600 mesh, used for grinding glass and fine polishing. Levigated abrasives are fine powders for final burnishing of metals or for metallographic polishing, usually processed to make them chemically neutral. Green rouge is levigated chromic oxide, and mild polish may be levigated tin oxide; both are used for burnishing soft metals. Polishing powder may be aluminum oxide or metal oxide powders of ultrafine particle size down to 600 mesh. Micria AD, of the Monsanto Co., is alumina; Micria ZR is zirconia; and Micria TIS is titania. Gamal, of the Fisher Scientific Co., is a fine aluminum oxide powder, the smaller cubes being 1.5 pm, with smaller particles 0.5 um. Cerox, of the Lindsay Div., is cerium oxide used to polish optical lenses and automobile windshields. It cuts fast and gives a smooth surface. Grinding compounds for valve grinding are
usually aluminum oxide in oil.
Mild abrasives, used in silver polishes and window-cleaning compounds, such as chalk and talc, have a hardness of 1 to 2 Mohs. The milder abrasives for dental pastes and powders may be precipitated calcium carbonate, tricalcium phosphate, or combinations of sodium metaphosphate and tricalcium phosphate. Abrasives for metal polishes may also be pumice, diatomite, silica flour, tripoli, whiting, kaolin, tin oxide, or fuller’s earth. This type of fine abrasive must be of very uniform grain in order to prevent scratching. Cuttle bone, or cuttlefish bone, is a calcareous powder made from the internal shell of a Mediterranean marine mollusk of the genus Sepia, and is used as a fine polishing material for jewelry and in tooth powders. Ground glass is regularly marketed as an abrasive for use in scouring compounds and in match-head compositions. Lapping abrasives, for finish grinding of hard materials, are diamond dust or boron carbide
powder.
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Last Updated ( Saturday, 01 March 2008 )
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