Cubic boron nitride. CBN is a type of cutting tool material offering a hardness that is second only to diamond. CBN tools are very effective at machining most steels and cast irons, but they are also very expensive. 

Manufacturers must continue to invest in new tooling technologies to stay ahead of their competition and to keep customers satisfied, and they need to pay close attention to total operating cost and process expenses.

This requires a delicate balance between the costs of tooling improvements and the benefits realized from those improvements.

One way that shops can achieve this balance is by optimizing their high-performance machining centers with tools that are coated with cubic boron nitride (CBN). The popularity of CBN has grown in machining over the past several years, and more shops are realizing its benefits.

CBN is second in hardness only to diamond. And, because of its high thermal stability and chemical resistance, shops often use CBN to machine ferrous materials for which diamond abrasives are unsuitable.

CBN helps to eliminate hand polishing, benchworking, finishing and grinding operations for materials that have hardnesses above 45 Rc, and CBN cutters cut more accurately to produce better parts and surface finishes.

With longe tool life and greater versatility as compared with traditional cutting tools, CBN tools deliver significant savings in time, extended run times and increased speeds and feeds. Shops that use CBN cutters also use fewer tools and make fewer tool changes. In addition, CBN tooling lets shops machine small details on parts in original setups to eliminate costly handling and secondary operations such as EDM.

At Hardmilling Solutions in Shelby Township, Mich., coowner Corey Greenwald said his shop has had great success using CB N cutters and inserts on its Makino vertical machining centers. The shop specializes in milling hardened materials, usually 60 Rc or harder.

“Some of our parts require very tight tolerances on materials such as crucible powdered metal, and if we cut those materials with regular carbide -– no matter how good the carbide or the coatings are -– it just won’t hold size for very long,” Greenwald said.

“With CBN cutters, we can run at much higher surface footage than with carbide, which lets us run at faster feedrates and save our customers money even in softer materials,” he added.

While CBN technology offers several benefits, some shops may find the technology expensive to implement. However, its advocates say that as with any improvement, CBN should be considered an investment that will pay for itself over time.

Co-max Tool estimates that while CBN-coated cutters may cost 40 percent to 50 percent more than traditional cutters, the cutters can double performance through improved cycle times, reduced setup time and reduced toolchange time because the tools last longer. The longer tool life provides savings on tool replacements. Additionally, the tools allow increased unattended machine time, so they can lead to lower labor costs.

However, to really unlock the potential of CBN coated tools and to experience greater efficiency and cost savings, shops need rigid accurate machines that work in combination with efficient controllers and software designed specifically for highspeed machining.