Metal Finishing Guide Book

2013

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Table I. Hardness of Abrasive Materials Abrasive Type Aluminum oxide (fused) Aluminum oxide (calcined) Tripoli-silica Silicon carbide Iron oxide (red rouge) Chrome oxide (green rouge) Chemical Symbol Mohs' Scale Al2O3 Al2O3 SiO2 SiC Fe2O3 Cr2O3 8-9+ 8-9+ 7 9.6 6 8-9 Silicon Carbide Silicon carbide (SiC) is of a crystalline structure that is harder than fused aluminum oxide. It is formed by mixing coke and silica in an electric furnace at approximately 1,900 to 2,400oC. The material is cooled, ground, and sifted to the required grit size similar to the processing of fused aluminum oxide. The crystalline structure of SiC is a hexagonal. Red Rouge The chemical formula for rouge is Fe2O3; it is also called jeweler's rouge. Its purity is 99% ferric oxide. The crystalline structure of ferric oxide is spherical. Rouge is used mainly on precious metals to give an exceptional high luster. Green Rouge The chemical formula for chromium green oxide is Cr2O3. The hardness of chromium oxide is 9 Mohs as opposed to iron oxide, which is 6 Mohs, and is used to produce an exceptional luster or color on ferrous as well as nonferrous metals. ISO 9001: 200 Certified These abrasives mentioned represent a small percentage of materiManufacturers of fine polishing al available to give a specific finish compounds for over 8 years. required on a particular substrate. See Table I for typical hardness val● BARS ● LIQUID ● PASTE ues. ● BUFFS ● BELTS Although the wheel speeds for buffing with grease bars will For Metal, Fiberglass, vary greatly from job to job and operator to operator, the figures Marble and Paint in surface feet per minute given All compounds are crystalline in Tables II and III will serve as silica free. a guide for hand buffing operaPrivate labeling available. tions. Buffing wheel speeds for automatic operation may vary CUSTOM KITS LUBRICANTS with the design of the machine SPECIALTY DEGREASERS and the contact of the work to the wheel. It can, therefore, be more 4800 South St. Louis Avenue definitely fixed without dependChicago, Illinois 60632, U.S.A. ing on the physical ability of the Phone: 773-847-1111 hand buffer to maintain the corFax: 773-847-3399 rect position and pressure against www.kocour.net the wheel. email: sales@kocour.net ● ● ● www.metalfinishing.com/advertisers 25

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