Glossary of Terms Commonly Used in the Abrasives Industry

Acid Washed - Abrasive grain washed with acid to remove iron and/or impurities.

Angle of Repose - The greatest angle to the horizontal made naturally by the inclined surface of a pile of abrasive when poured from a designated height. Usually a measure of the ease with which the material will flow.

ANSI - American National Standards Institute - Organization maintaining standards used in the industry.

Apparent Specific Gravity - The ratio of a mass of solid or liquid to the mass of an equal volume of distilled water.

Aspect Ratio - The ratio of the length of a particle to its width.

ASTM - American Society of Test Materials - Organization maintaining technical standards for a wide variety of industries.

Ball Mill - Equipment used to reduce particle size by breaking agglomerations of particles into individual particles and larger particles into smaller ones, and to modify particle shape.

Bayer Process - A process for the purification of bauxite (aluminum ore). The ore is digested with a sodium hydroxide solution which dissolves the alumina and precipitates oxides impurities such as iron, silicon, etc. The solution is then filtered and the alumina precipitated as a hydroxide. This is used as a feed stock for white fused and calcined alumina.

BCI Test - Buck and Company Incorporated - Test equipment for analyzing abrasives for free iron.

Bolting Cloth - Mesh used for making sieves for sifting equipment.

Bonded Abrasives - Abrasive grain used in Grinding Wheel applications.

Bulk Density - Sometimes referred to as "density" or "loose packed density" (LPD). Weight (grams) per volume (cubic centimeters) of loose packed abrasive grain. Generally indicative of the shape of the grain.

CAMI - Coated Abrasives Manufacturing Institute - Organization of coated abrasive manufacturers.

Capillarity - Ability of abrasive grain to be wetted by capillary action. Usually an indication of grain cleanliness.

Cerium Oxide (CeO₂) - Naturally occurring deposits are usually a mix of Cerium and other rare earth oxides (REO's), such as Rubidium Oxide and Tantalum Oxide. Color varies from off-white (buff) to reddish brown, depending on the chemical content. Softer than Alumina and Silicon Carbide; primarily used for polishing glass, quartz crystals, etc.

Chemical Composition - A chemical analysis of an abrasive.

Coarse - Composed of comparatively large particles.

Coarse Grading - Abrasive grain with too many large particles. A sieve analysis with too much material retained on the largest opening sieves in the specification.

Coarse Grits - Generally particles extremely large for the abrasive grain size.

Coated Abrasives - Abrasive grain used in the sandpaper industry.

Colloid - A finely divided dispersion of one material in a second continuous phase (usually a liquid) in which the particles range in size from one nanometer to one micron. May be used for very fine polishing or as a feedstock for non-fused abrasive manufacture.

Coning and Quartering - A method for getting a smaller representative sample usually from a larger sample. The grain is arranged into a conical pile and divided into quarters. Alternate quarters of the pile are combined, piled and quartered similarly until a small representative sample is obtained.

Corundum - Naturally occurring Aluminum Oxide.

Crude - Large pieces of abrasive in an ingot form (after furnacing) or after primary crushing.

Crusher - Size reduction equipment causing the separation of a solid into pieces. Some examples are jaw, gyratory, roll, and hammermill.

Crystallography - Description of the size or shape of a crystal. For fused abrasives, usually determined by degree of cooling an ingot after furnacing. For SiC, alpha silicon carbide forms hexagonal crystals. NOTE: Crystallography refers to the shape of the crystal formed, and is distinct from the shape of the actual abrasive granules, which may be modified by crushing, milling, etc.

Density - Sometimes used to describe apparent specific gravity or bulk density.

Dust Fines/Extreme Fines - Particles much too fine for the abrasive grain size.

Electrical Resistance - A method of measuring particle size distribution, used especially for microgrits.

Emery - Naturally occurring mineral, an intimate mixture of corundum and mineralized iron oxide.

FEPA - Federation of European Producers of Abrasives - European organization which maintains abrasive specifications (FEPA F - Bonded) (FEPA P - Coated).

Fine - Composed of comparatively small particles.

Fine Grading - Abrasive grain with too many small particles as specified on a sieve analysis.

Flint - A silica-based mineral often used as an abrasive.

Free Iron - Iron in abrasive grain usually originating from the crushing equipment.

Friability - Relative breakdown of the abrasive grain through attrition (grinding, blasting, milling)

Furnacing - General method for producing abrasive crude either by fusion (alumina based) or electro chemical reaction (Silicon Carbide).

Fusion - Melting of raw materials (generally in an electric arc furnace) to make an abrasive ingot. Generally associated with Alumina based abrasive grains.

Garnet (Al₂O₃.3FeO.3SiO₂) - A naturally occurring abrasive, reddish brown in color, blocky to sharp in shape, slightly softer than Alumina (8 on Mohs scale). Used in a variety of industrial applications.

Grade - Definition of size of abrasive grain.

Grit - Similar to grade.

Hardness - Resistance to denting or scratching usually measured the Moh's scale or Knoop.

Heat Treating - Heating an abrasive grain to impart a certain property (harder, tougher, cleaner)

ISO - International Organization for Standardization- International organization involved with specifications and quality systems.

JIS - Japanese Industrial Standard, published by the Japanese Industrial Standards Committee in conjunction with the Japanese Standards Association.

LPD - Loose packed density. Same as bulk density.

Macrogrits - Generally abrasive grain sizes coarser than 240 or 280 grits.

Mag (Magnetic) Treat - Passing abrasive grain through a magnetic field to remove free iron.

Melting Point - The temperature at which a solid turns to a liquid.

Mesh - Generally interwoven wire screening used to sift or test abrasive grain. Sometimes wrongly used to describe abrasive grain size.

Microgrits - Generally abrasive grain sizes finer than 220 or 240 grits.

Micron - One millionth of a meter. Generally used to define average particles size of microgrits (powders).

Mixed Grits - Generally a condition where two grit sizes are unintentionally mixed together.

Nanometer - One billionth of a meter (one thousandth of a micron).

Netronics - Instrument (Buck and Company, Inc.) Used for measuring free iron.

Packed Density - Another term for tap density.

Particle Size - Average diameter of an abrasive grain.

Pour Density - Bulk density.

Pycnometric Density - Apparent specific gravity tested with a pycnometer.

Refractories Abrasive - Abrasive grain manufactured for the Refractory industry.

Riffle - A sample splitting device used to separate a large sample into a small representative sample.

Rotap - Instrument used to sift abrasive through sieves to obtain a particle size distribution measurement.

Sample Thief - A tubular instrument with a closed, pointed end having holes down one surface used for procuring a representative sample of abrasive grain.

Screen: 1) A sieve. 2) A machine with screening surface(s) used to classify materials by size.

Screen Sizes - Another term for macrogrits.

Sedimentation Sizes - Another term for microgrits.

Sedimentometer - A device for measuring particle size distribution using the time it takes a sample of material to settle a given distance, using Stokes Law.

Sieve - Generally, interwoven mesh mounted on a frame and used for testing or sifting abrasive grain.

Sieve Sizes - Another term for macrogrits.

Sinter - To coalesce into a single mass without actually melting.

Size Distribution - A measured size range of abrasive particles.

Spherical Equivalent - A means of reporting the size of particles regardless of shape based on their volume, in which the particle size is reported as the diameter of a sphere of the same volume.

Standard Sand - An abrasive of a known particle size distribution when tested on a calibrated instrument; used to verify calibration of other test instruments (such as sieves; see Appendix 3).

Surface Treatment - Coatings added to abrasive particles to impart certain characteristics (wetability, flowability, retention).

Tap Density - Generally a bulk density of a packed sample. Generally used for powders.

Test Sieve - A specially manufactured sieve used for testing particle size.

Toughness - Resistance to abrading of abrasive grain.

Viscosity - The resistance of a liquid to shear forces, and thus its resistance to flow.