Abrasive Grains

There are several naturally occurring and manufactured grains used to make abrasive papers, wheels, stones, etc., each with characteristics more or less suitable for a particular application.

Natural abrasive grains

Crocus - A natural abrasive of iron oxide particles. Used mostly for cleaning and polishing soft metals.

Emery - An abrasive that is a natural composite of Corundum and Iron Oxide. The grains are blocky, cut slowly, and tend to polish the material being abraded.

Garnet- A very sharp naturally occurring abrasive grain, red in color, made by crushing semi-precious garnet material. Cuts very quickly when new. Fractures quickly, keeping it sharp. Perfect for sanding wood end grains or for final-finish sanding of wood. Very economical. Still used occasionally in the woodworking industry.

Flint - A natural abrasive not commonly used today. A form of quartz, it is too soft for most types of sanding. Only used for hand sanding.

Manufactured abrasive grains

Aluminum Oxide - A grain made by fusing the mineral bauxite. A very strong, blocky, hard, and tough grain. The most commonly used abrasive for sanding wood and solid surface materials and grinding ferrous and non-ferrous metals. Normally brown or reddish-brown in color.

Alumina Zirconia - A high performance alloy of aluminum oxide and zirconium oxide. A very hard and sharp grain that works well for grinding of stainless steel, spring steel, titanium and other hard steels and for dimensioning of wood. Designed for heavy duty stock removal for metal and wood, with a self-sharpening characteristic. Belts are normally blue in color.

Silicon Carbide - A sharp, very sharp, hard, and brittle grain made from coke and silica sand, best suited for sanding of glass, plastics, rubber, ceramics, solid surface materials and some non-ferrous metals. Also used for sanding softwoods, painted or otherwise finished surfaces. Cuts very well under light pressure. Normally black in color. Carborundum is a trade name for certain abrasive products, often misused as a generic name for silicon carbide.

Stearate

Zinc stearate is a dry lubricant added to the surface of coated abrasives (usually sheet or disc goods) which prevents loading of soft materials such as resinous woods, sealer coats, paint and other finishes and when working with soft ferrous or non-ferrous metals. Not an abrasive grain. Normally white-gray in color.

Tags: Finishing - Metalworking - Woodworking - Supplies - Tools