TABLE OF CONTENTS Are materials used to polish or machine metals, wood, stone, glass, and other materials by the cutting action of the small grains of the material. (Abrasive machining is described and illustrated in 3C). There are two kinds of abrasives, natural and man-made. Natural abrasives include aluminum oxide ("corundum"), emery (impure aluminum oxide), diamond, sand, crushed garnet, quartz, tripoli, talc, and pumice. These materials are mined, crushed, classified by size and shape, and usually bonded together in a grinding wheel, stone or block, or bonded to paper or cloth. Man-made abrasives are silicon carbide (SiC) "Carborundum", aluminum oxide (Al 2O 3) "Alumina", boron nitride (BN), and boron carbide (B 4C) made by various chemical processes.
Is made from pure sand, coke, sawdust, and salt. The mixture of these ingredients is placed in a long, trough-like furnace and heated by an electric current from graphite electrodes. Temperatures up to 4400 F (2400 C) cause a complex chemical reaction that yields SiC and carbon monoxide. Crushing of...
