Metabo has developed an internationally recognized code to identify the different raw materials and characteristics of their products. This wheel code system tells you three main features of the wheel:
Here's what it means:
Aluminum Oxide = A
Zirconia Alumina = ZA
Silicon Carbide = C
The first symbol in the code identifies the grain type.
The aggressiveness of the grain is largely determined by grain size. The larger the grain, the more aggressive the cut. Grain sizes are measured using a system of wire mesh sheets. Metabo uses grain sizes from 60 meshes (finer) to 16 meshes (coarser) to the inch. This is the second number on the code.
The bond holds the grain in place until the grain's useful working life is finished. The international grading system for Bond Hardness works on an alphabetical scale with A as the softest, and Z as the hardest. The industry generally uses grades between M and V: M being the softer grade and V being very hard. This is the third symbol on the code.
A 24 R
Aluminum Oxide grain, 24 grid grain size, and in the mid range on the bond hardness scale. A phenolic resin bond and fiberglass reinforcing.
ZA 24 T
Zirconia Alumina grain, 24 grit grain size, and toward the harder end of the scale (better suited to zirconia alumina, with its greater friability). A very aggressive long life wheel. A Phenolic resign bond and fiberglass reinforcing.
C 30 S
Silicon Carbide grain, 30 grit grain size, and a bond moving toward the higher (harder) end of the scale. A wheel with a reasonable life. A phenolic resin bond and fiberglass reinforcing.