Abrasive grains are any hard, sharp material that can be used to wear away another material when one or the other is moved in pressure contact. Abrasive grains are produced from a variety of different: alumina (Al2O3), silicon carbide (SiC), carbon boron nitride (CBN), Diamond, etc. It is the hardness and sharp particle shape of these materials that makes them abrasive.
Grit Numbers for Abrasives

The Grit number is the designation of abrasive grain size, reflecting the number of the smallest openings per linear inch in the screen through which the grain will pass; these can range from No.4 to No. 2500. The particle size (Dv ) can vary from several millimeters to less than 2 microns.
Applications of Abrasives

These materials are used in a variety of different applications when incorporated into a suitable matrix; for example as sandpaper, in grinding wheels, for lapping, for wire-sawing, as honing sticks, for sandblasting etc.

Different applications may demand different grain shapes and this has a significant influence on the abrasives performance.
Manufacture of Abrasive Grains

The main grain crushing techniques are impact crushing, crushing by pressure, crushing by abrasion or a combination of all three.
Influencing Grain Shape During Manufacture

Manufacturers of abrasive grains can influence the grain shape by employing different crushing methods, but controlling the shape has so far been more difficult.

Depending on customer preferences, and end use, grain shape requirements differ widely.
Traditional Quality Control Parameters

The International Standards for manufacturing of abrasive grains describe methods for measuring bulk density. Bulk density gives an indication of grain shape, but several other product characteristics also influence the bulk density, i.e. Particle Size Distribution, flow ability and surface condition.
Shape Characterization Of Abrasives

A new instrument (Sysmex FPIA- 2100) for the rapid particle size and shape characterization has recently become available. Measurements from this instrument have enabled a more precise way of characterizing different grain shapes and differences in grain shape between otherwise similar products.
Operation of the Sysmex FPIA-2100

The Sysmex FPIA-2100 uses sheath flow and patented high speed image analysis for rapid particle size and shape characterization, typically generating data within 5 minutes. Traditionally, shape characterization was performed using conventional microscopy with image analysis and this can take up to 2-3 hours per sample.