Whenever possible, grinding processes should always be made with some mode of cooling. Compared with dry grinding, wet grinding substantially improves the life of the grinding wheel and the risk of causing thermal damage to the workpiece drops dramatically. Also, cooled grinding allows a much higher removal volume which, ultimately, is a measure of the efficiency of a grinding operation.
Using pure grinding oil as coolant has provided by far the best results, especially when using CBN grinding tools. Compared with other cooling media, the life of the grinding wheel rises by a factor of 3.
Highly important criteria for successful cooling during the grinding process are the positioning and the configuration of the nozzle and the coolant pressure.
The coolant jet should always hit the grinding wheel at an angle of 20°, as close as possible to the grinding contact zone.
The exit opening of the nozzle should be sharp-edged, undamaged, and only marginally wider than the grinding rim (e.g. grinding wheel 10 mm in width / nozzle 11 mm in width).
To safeguard the efficiency of the cooling, the exit speed at the mouth of the coolant nozzle should correspond to the perimeter speed of the grinding wheel (Vs). The required coolant pressure (pk) is shown in the table below.
Wheel speed (Vs) and required coolant pressure (pk) at the nozzle