Grinding wheels vary greatly from each other due to the large number of grinding applications. A grinding wheel is commonly divided based on its abrasive material, bond, grain size, hardness, structure, density, and size.
GRINDING (NON-DIAMOND) DISCS
A - Brown Aluminium Oxide (Alumina):
A hard, tough, and cost-effective grain suitable for a very wide range of applications. Commonly used for centerless grinding, surface grinding, cylindrical grinding, and coarse grinding.
WA - White Aluminium Oxide (Alumina):
Harder and more friable than Brown Alumina, which contributes to the cooling effect during the grinding process and results in high grinding performance. Suitable for grinding of most steel types, other high-strength and high-hardness materials, and can also be used for threading, gears (mixed with other grains), and thin-walled parts.
AWA - Brown & White Aluminium Oxide (Alumina):
A brownish-colored abrasive grain combining the characteristics of Brown and White Alumina, resulting in high performance for large grinding areas. Suitable for grinding of cast iron crankshafts and camshafts, and commonly used for centerless grinding wheels.
BA - Blue Fired Aluminium Oxide (Alumina):
A brown fused alumina that is specifically treated at elevated temperatures resulting in significantly high strength and toughness. Highly suitable for centerless wheels and large diameter or cutoff wheels.
PA - Pink Aluminium Oxide (Alumina):
A peach-red abrasive grain that is duller than White Alumina. The abrasive cutting edge has a sharp edge and is highly durable. Suitable for cutting tools, gauges, precision parts, threaded workpieces, and other applications, especially when high surface finish is needed.
RA - Ruby (Red) Aluminium Oxide (Alumina):
A ruby fused alumina with high levels of chromium oxide, enhancing the friability of the wheel. Ruby fused alumina possesses unique fracturing properties that provide an extremely cool grinding process. Highly suited for grinding heat-sensitive materials, surface grinding of high alloyed steel, ductile steel, valves, and the grinding of thin plates.
SA - Single Crystal Aluminium Oxide (Alumina):
A grayish-white abrasive grain with a hard, tough, single-particle spherical crystal, with a good multi-row cutting edge. Strong breakage resistance. Suitable for grinding of high-vanadium, high-speed steel, austenless steel, high-speed steel, and alloyed steels.
C - Black Silicon Carbide:
This abrasive grain is characterized by high hardness, self-sharpening properties, and cool cutting. Suitable for cutting stone, glass, and ceramics, the grinding of non-ferrous metals, and the polishing of stone, marble, and granite.
GC - Green Silicon Carbide:
An abrasive grain with hardness only second to boron carbide and diamond. More friable than black silicon carbide, suitable for gray iron, chilled iron, brass, soft bronze, aluminum, as well as stone, rubber, and other non-ferrous materials. Highly suitable for grinding carburized cutting tools.
NG - Ceramic Aluminium Oxide (Alumina):
A high-purity grain manufactured in a gel sintering process, resulting in an abrasive grain with the ability to fracture at a controlled rate at the sub-micron level, constantly creating thousands of new cutting points. This abrasive is exceptionally hard and strong. Primarily used for precision grinding in demanding applications on steels and alloys. The abrasive is normally blended in various percentages with other abrasives to optimize its performance for different applications and materials.
The bonding material in a grinding wheel holds the abrasive grains inside the wheel; it holds the grains together and needs to withstand the grinding force and rotary forces of the abrasive machining process. It uses a variety of bonds tailored for each wheel and application.
V - Vitrified Bond:
A cost-effective solution for a wide selection of our wheels.
V-L - High-end Series of Vitrified Bonds:
The latest generation of bonds, providing an optimal ratio between binder and abrasive grains. Enhances holding ability. This high-end bond series is well-suited for operations.
B - Resinoid Bond.
BF - Reinforced Resinoid Bond.
The size of individual grains in the wheel corresponds to the number of openings per linear inch in the final screen size used to size the grain. In other words, higher numbers translate to smaller openings in the screen grain. The coarser the grain, the larger the size of the material removed. Coarse grains are used for rapid stock removal where finish is not important. Higher numbers (such as 70, 100, and 180) are fine grit wheels. These are suitable for imparting fine finishes, for small areas of contact, and for use with hard, brittle materials.
The strength of a bond is designated in the grinding wheel. The bond is said to have a hard grade if the spans between each abrasive grain are very strong and retain the grains well against the grinding forces tending
to pry them loose. A wheel is said to have a soft grade if only a small force is needed to release the grains. It is the relative amount of bond in the wheel that determines its grade or hardness.
Please note that if dry grinding is required, choosing a softer wheel than one used in wet grinding should be strongly considered.
E-H: High precision grinding, grinding of superfine and super-soft materials.
E-J: Creep feed grinding for a wide range of alloys.
H-J: Grinding of non-ferrous metals; continuous and non-continuous gears.
H-K: Grinding of high-speed steel and high alloy steel.
K-N: General-purpose hard grinding wheel.
M-R: General-purpose medium-hardness grinding wheels.
S-Y: Super-hard grinding wheels.
STRUCTURE AND DENSITY:
The structure of the wheel refers to the spacing of abrasive grain within the wheel and is measured in terms of volume content of the grain within the wheel. In dense structures, the pores are small and the abrasive grain is closer together. In an open structure, the pores are larger and the abrasive grains are situated further apart.
Closed - 5, 6, 7
Medium - 8, 9, 10
Open - 11, 12, 13, 14, 15