Silicon carbide was
discovered by the American inventor Dr. Edward G. Acheson
in 1891 while attempting to produce artificial diamonds from coke and silica
sand. Finding that these new crystals
approximated the hardness of diamond and immediately realizing the significance
of his discovery, Acheson applied for a U.S. patent. His early product
initially was offered for the polishing of gems and sold at a price comparable
with natural diamond dust. The new compound, which was obtainable from cheap
raw materials and in good yields, soon became an important aaaaaaaaaaaaaaaaaindustrial abrasive.
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As an abrasive, Silicon Carbide is black in color and is the
hardest and sharpest of the minerals used commonly in coated abrasives. It’s harder
than Aluminum Oxide but considerably more friable—which means that it fractures
readily, exposing new sharp edges. Silicon Carbide is most effective with non-
ferrous metals such as brass, copper, bronze, magnesium, titanium and aluminum
where fast, cool cutting is desirable.
Non-metallic applications include ceramic, stone, glass, plastic,
leather and rubber. Silicon Carbide is
superior to any other abrasive in its ability to penetrate and cut faster under
light pressure.
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Aluminum Oxide
was introduced in 1900 by CT Jacobs. It
is produced from the raw mineral Bauxite where it is fused in electric arc
furnaces at temperatures up to 2600’ C, which is a temperature 800’ C hotter
than lava in a volcano! The AO ingots are cooled and then crushed with a roll
crusher to produce a large volume of splintery, sharp and friable abrasive
particles that break down easily to remain sharp and produce a minimum of heat
buildup. The crushed AO is then sized into the various grits used in producing
coated abrasive products.a
Aluminum Oxide remains the most popular abrasive used in
sanding products, as it is considered the most “all purpose” abrasive. It is a reddish-brown in color, extremely
tough and its blocky shape facilitates the penetration of tough materials
without excess fracturing or shedding. It is specified for applications on high
tensile materials such as carbon steel and alloy steel as well as wood,
composites and solid surface.
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These traditional synthetic minerals used in abrasives offer
many advantages over the traditional naturally occurring minerals. Synthetic
minerals are consistent without unforeseen impurities. In addition, we have the
technology to control the grain characteristics in a synthetic mineral. Grains for coated abrasives are different
than the grains used in grinding wheels. They are elongated to achieve the best
bonding results and abrasive performance.
Aluminum Oxide is manufactured in two levels of abrasive
grain surface density: closed coat and open coat. A closed coat product is one
in which the abrasive grains completely cover the surface of the backing. The
greater number of “abrading points” per square inch results in a larger amount
of material being removed before the product becomes worn out. An open coat
product is one in which the abrasive grains cover approximately 50% to 60% of
the coat side of the backing. Open coat AO frequently cuts faster and provides
a greater resistance to loading, which makes it an ideal choice for sanding on
softwoods.
