The specific cutting action of abrasive wheels is determined by the type and size of the abrasive grains, the type of bond which holds the abrasive grains together, and the amount of open spaces or porosity in the wheel.
ABRASIVES: The abrasive grains used in grinding wheels range in size from the very large dimensional grains, called “coarse” grits down to very tiny grains which are in “fine” grit wheels. Aluminum Oxide is the most commonly used type of abrasive grain for cutting most ferrous materials. Other specific applications may use Silicon Carbide in their wheels while Zirconium Oxide or ceramic grain combinations may be used for premium grades of wheels. The size and type of the abrasive grains used in a wheel will vary depending on the specific cutting application, the material being cut and the desired finish of that material. The efficient grinding action of cutoff wheels is due to the constant replacement of sharp cutting edges. When the abrasive grits become dull during use, the grain may either fracture to form new cutting edges or break away from the bond, exposing sharp, new grits.
RESINOID BONDS: Our cutoff wheels are bonded together with high quality, phenolic resins. These synthetic resins and fillers are mixed with the abrasives in specific percentages to achieve the desired hardness of the wheel. Fillers are used for heat resistance and to add to the bonds’ strength. The hardness or grade of a wheel is measured by how strongly the bond holds the abrasive grains from being torn away from the wheel during its’ use. A soft grade wheel is normally used when cutting hard materials and a hard grade wheel is used for soft materials.
POROSITY: Wheels are made with varying densities depending on what grain spacing works best. Wheels with an open structure have a wide grain spacing to allow for better removal of the workpiece chips, where as wheels with a closed, denser structure have a tight grain spacing to better hold their shape.
FIBERGLASS REINFORCEMENT: A woven mesh of fiberglass strands is added to wheels for more severe applications where there is a greater potential for wheel breakage. This fiberglass reinforcement adds to the safety factors of the wheel by increasing its strength and allowing it to be run at a higher operating speed.
WHEEL MARKINGS: A wheel “specification” gives us the required information on what components are in the wheel.
A typical, general purpose wheel may be marked as A46-TBF which from the following chart can be determined to be a wheel with Aluminum Oxide, 46 grit, a medium/hard T hardness, Resinoid bond and externally reinforced with fiberglass.
|
Abrasive |
Grain Size |
Hardness |
Bond Type |
Reinforcement |
Specials (Optional) |
|
A = Aluminum Oxide |
16 = Coarse |
J =Softest |
B = Resinoid |
No F = NO Reinforcement |
ex: RS = Rough Sides |
|
C = Silicon Carbide |
20 |
.. |
R = Rubber |
F = Externally Reinforced |
|
|
CA = Silicon Carbide &
Aluminum Oxide |
24 |
M = Soft |
E = Shellac |
F1 = Internally Reinforced |
|
|
SG = Ceramic Grit &
Aluminum Oxide |
30 |
.. |
|
|
|
|
NZ = Zirconium Oxide &
Aluminum Oxide |
36 = Medium |
O = Medium |
|
|
|
|
|
46 |
.. |
|
|
|
|
|
54 |
U = Hard |
|
|
|
|
|
60 |
.. |
|
|
|
|
|
70 |
Z = Hardest |
|
|
|
|
|
80 = Fine |
|
|
|
|
|
|
90 |
|
|
|
|
|
|
100 |
|
|
|
|
|
|
120 |
|
|
|
|
|
|
180 |
|
|
|
|
| 
