Grinding fluids (coolants)
Many resin bonded CBN and diamond grinding wheels can be used tor dry grinding. Whenever possible, however, wet grinding operations are preferable and more efficient. Neat (pure) grinding oil is best suited for the use ot CBN. In practice, however, workshop conditions often dictate the use ot other types ot grinding fluids. Solutions with a high percentage ot mineral oil in the concentrate are also recommended (40 to 50%) when using CBN. Synthetic grinding fluids, however, are not ideal for CBN grinding processes. On the other hand, synthetic grinding fluids are suited tor processes using diamond grinding wheels. |
Selection of grinding fluids
The selection of grinding fluids has an enormous influence on the overall performance of a grinding wheel. The following graph illustrates how decisive differences in output, as measured by the G-ratio, can be achieved just by changing the type of grinding fluid. In the case of tungsten carbide, however, oil will onIy improve the material removal rate by 10%. Oil will, however, extend the tool life by a factor to two to three in comparison to water based grinding fluids. Additionally, oil will not leach out cobalt if the oil does not contain any free fatty acids. |
Grinding fluid recommendation
The following table illustrates which grinding fluid is suited for which material to be ground. The selection of a suitable grinding fluid should be made in close collaboration with a competent and reputable supplier or manufacturer of grinding fluids. For tungsten carbide select an oil of very low viscosity (1.5 to 3 Cst at 40 °C). Double the flow volume of oil in comparison to water based grinding fluids as oil has a lower thermal conductivity rate. |
|
|
Soluble oil |
Micro emulsion* |
Synthetic |
Neat (pure) oil |
|
Steel |
|
|
|
|
|
Cobalt |
|
|
|
|
|
Tungsten carbide |
|
|
|
** |
| Glass |
|
|
|
|
|
Ceramic material |
|
|
|
| | * Micro emulsion = size of oil droplets < 2um (concentration 2-5%)
** Low viscosity oil |
