THROUGH-INSERT COOLANT DELIVERY TAKES CENTER STAGE

With the discovery and development of cemented carbide for cutting tool use in the 1920s, the history of cutting tool development has progressed largely on a linear basis, proceeding from one advance to the next. Additions of alloying elements such as titanium, niobium, and tantalum in the 1930s, along with Philip McKenna's breakthrough development of a tungsten titanium carbide alloy in 1938, significantly raised metal cutting performance and pioneered more efficient metalworking in such industries as automotive, aerospace, energy, and many others.

Technologies related to cutting tool development, such as coatings and how they are deposited, more powerful computer-aided design (CAD) programs, more sophisticated process controls for sintering, and multi-axis machine tools along with high-pressure coolant systems, have largely progressed in the same manner, moving from one development to the next.

Now another giant step forward in integrated tooling design and coolant delivery is being taken by channeling coolant through the insert, directly to the edge where the tool cuts the material, ensuring better cutting performance through more efficient coolant delivery, heat transfer, lubricity, and improved chip control.

Yet ever-increasing global competition, pressure for reducing costs, and tightening economic conditions around the world continue to demand increased productivity. What would be the next big thing?

Metal cutting coolants have been around for at least 200 years. Notable landmarks in their use have been through-the-spindle delivery systems, nozzles in threaded seats in cutter bodies, and independent, high-pressure pump systems up to 4500 psi or even higher. Better coolant delivery has its place in helping improve tool life or contributing to improved chip control, but it also has its limitations. Better nozzles and higher pressures help improve coolant application, but in many cases, flood coolant remains wasteful and can have a deterrent effect on chip control by forcing chips back into the cut where the subsequent recutting helps shorten tool life.

Through-insert coolant delivery brings together precise metal cutting geometries and grade development with integral coolant channels for the most precise coolant placement, taking place directly at the cutting edge beneath the chip. Metal cutting generates a lot of heat, which can shorten tool life. Through-insert coolant delivery applies coolant directly where it does the most good: to remove heat and reduce friction. In addition, coolant only comes out on the edge or quadrant doing the cutting. Inserts remain indexable for maximum use.

Initial tests also reveal increased cutting performance at lower coolant pump pressures. In titanium machining (Ti-6Al-4V at 300 sfm, 0.008 ipr, and 0.050 depth of cut), through-insert coolant delivery showed a 75 percent improvement in relative tool life at 100 psi coolant pressure compared to the same tooling grade using flood coolant also at 100 psi. Not only is 75 percent longer tool life a notable extension of cutting performance in its own right, it nearly matched the same grade cutting at 1,000 psi.

We won't know the full range of benefits until more people use through-insert coolant delivery in their production processes, but consider the following:
• Manufacturers can increase their effective capacity by producing more parts in less time.
• Markedly less coolant can be used, improving a manufacturer's environmental impact.
• Machine-tool builders could simplify coolant systems and use reduced-pressure pumps, lowering costs and overall power consumption.
• Improved chip control could lead to more efficient chip conveyors.

Through-insert coolant delivery represents a significant step forward in tooling development. Like all such developments, it is the product of many dedicated people in many specialties: materials science, mechanical engineering, powerful CAD modeling and sophisticated CNC controls. It is at the same time a design and engineering breakthrough, one that will prove itself in the reality of more efficient manufacturing. When future histories of tooling development and manufacturing technology are written, this will stand out as a significant milestone.

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Bernard North is the vice president of product engineering at Kennametal Inc., 1600 Technology Way
Latrobe, PA 15650, 800-446-7738, Fax: 724-539-5022, www.kennametal.com.