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Calculating the dimensions of the grinding nozzle orifice is critical in order to achieve the proper flow and application of the grinding fluid through the arc of cut. Firstly, the well documented and tested “rule of thumb” is that the fluid should be applied at the rate of 1 to 1.5 gpm for every horsepower used in the grind. Ref. Cutting and Grinding Fluids - Selection and Application (Second Addition). Link to Technical reference books. (Click on the book - right and below.)
Next, the speed of the grinding fluid should be equal to, or slightly faster than, the peripheral speed of the grinding wheel, at the point where the fluid hits the wheel. A rather complex set of fluid dynamics formulae can be used to calculate the fluid flow based on the pump flow and pressure characteristics and some estimated factors for nozzle efficiency and fluid friction losses. Rather than make these calculations it is a simple task to specify the pump characteristics to the machine tool builder, as follows:
The pump, for the main fluid supply nozzle, needs to be able to deliver the grinding fluid at maximum peripheral wheel speed, for the maximum width of grinding wheel, for the maximum power available to be used in the grind.
The proper pump specification will then insure that there is sufficient pressure to drive the fluid through any nozzle under the most extreme conditions. For any lesser parameters, there will be a surplus of pump pressure. All you will need is a flowmeter in the line to check the flowrate. Click on the flowmeter link (above).
Calculate the nozzle depth "d" from the formula on the left. Wheel peripheral speed, in inches (5800 x 12) = 69600 multiplied by the area of the nozzle (width 1.125 x depth "d") in sq. inches, is equal to the pump flow rate, in gpm, x 231. The nozzle depth "d" is therefore approximatley 0.100".