by Kip Hanson
Anyone who’s placed their finger over the end of a garden hose and used the resultant stream of water to spray off the sidewalk knows the effectiveness of high velocity fluid.
Scientists began exploring how this force could be harnessed for manufacturing more than 60 years ago, when Reginald J. S. Pigott, director of the engineering division of Gulf Research and Development Co. filed a patent in 1951 on the use of high velocity cutting fluids to improve tool life in metalcutting operations. Since then, a number of companies have developed high pressure coolant (HPC) equipment for use on CNC lathes and machining centers.
One of these is Chipblaster. President Greg Antoun says the problem with non-HPC coolant is that metalcutting temperatures are well above the boiling point of water, causing cutting fluid to vapourize before it can touch the workpiece where it’s needed most–in the cutting zone. But by forcing a stream of pressurized cutting fluid through a triangular nozzle, velocity sufficient to break through the vapour barrier and strike the workpiece is made possible.
“People talk about high pressure, but the only thing pressure does is create velocity,” Antoun says. “Even then, you have the Bernoulli effect, which tends to pull apart a stream of water. It’s the triangular nozzle shape that makes HPC possible. The points of the triangle are sacrificial, protecting the stream of liquid as it flies through the air, and making certain there’s still enough velocity to reach the cutting zone.”
Antoun says HPC does such a good job at cooling the insert and the area immediately around it that machinists should (usually) increase cutting parameters to compensate. This raises the amount of heat generated in the cut and brings carbide back to its optimal working range. The result? Tool life is greatly improved. Feeds and speeds can often be doubled, tripled, or more, with a commensurate increase in productivity. And the cooling effect also aids in cold working the material as it flows across the insert face, thus helping to break the chip. Simply put, HPC is a no-brainer for the majority of machining operations.