Tech Talk
How should a “Coolant Nozzle” be set up for grinding?
The proper delivery of coolant (grinding fluid) into the grinding zone is of utmost importance. Adequate volume and pressure are not sufficient if the coolant jet’s velocity is either too high or too low. The exit velocity of the coolant jet should be roughly equal to the grinding wheel’s surface speed. This will ensure that the wheel will transport coolant into the grinding zone. Equal velocity fluid delivery will be achieved if the coolant jet “clings” to a 30 to 40 section of the grinding wheel’s periphery.
Nozzles made up of short interlocking plastic tubes are adequate for general toolroom application. For high volume production, however, these interlocking tubes are insufficient as they create turbulence, spray in all different directions and prevent achieving equal velocity fluid delivery. Proper nozzle design should feature a long straight section of at least 50 mm length and a very sharp edge at the point of exit. The nozzle should be set on an angle of about 20 .
Alternatively, the so called shoe nozzle design ensures equal deliveries at a much lower pressure. A chamber fitting snugly (o.5 mm max. gap) around the grinding wheel, is flooded with copious amounts of fluid at low pressure. The wheel will pick up the grinding fluid and accelerate it to equal surface speed. Additionally, the shoe nozzle acts as an air scraper or air dam which removes the layer of turbulent air (air jacket) around the grinding wheel.
