Chart: Abrasive Types

2″x72″ grinder belt abrasives come is a wide (and evolving) range of materials and formats.

Here’s my understanding of the abrasive materials (additions and corrections welcome):

Abrasive Notes
Aluminum Oxide General purpose. Low price. Limited life.
Silicon Carbide Aggressive but short lived on steel. Better for soft materials – like handle materials – or in fine grits where less pressure is used.
Alumina Zirconia aka Zirc Better for heavy-duty steel stock removal. Requires pressure to keep cutting (to break out new cutting surfaces).
Ceramics Best overall for heavy-duty stock removal. Higher cost should be offset by long life of the belts.

And then there is the way in which the abrasive is attached (and structured) on the belt. And again – let me know if you have additions or corrections.

Type Notes
Standard The abrasive is evenly distributed on the belt.
Gator The abrasive is stacked thickly in a diagonal grid of brick-like mounds – with spaces between. Long lasting, cooler cutting.
Seeded Gel (SG) The grit is suspended in a gel. Spent grit is pulled out, revealing new sharp grit, which keeps the belt sharper, longer.
Closed Coat The grit completely covers the backing. This makes a very even and aggressive belt, but is subject to clogging with soft or gummy materials.
Open Coat The grit covers 50% to 70% the backing. The belt may not be as aggressive as a closed coat version – but it won’t clog up as easily on softwoods, non-ferrous metals, or synthetic handle material.