8 Reasons PCBN Hard Turning Shines in Finishing Operations

By Chad Miller, Product Manager – Advanced Materials

Recent advances in cutting tool technology have increased the acceptance of hard turning as a finishing operation of critical surfaces. In fact, hard turning with tools made from polycrystalline cubic boron nitride (PCBN) is more productive, cost-effective and can produce better results than grinding when finishing hardened steel parts between 45 and 64 HRc.

Top eight reasons hard turning with PCBN tools is better than grinding:

1. A CNC lathe costs up to 50 percent less than a grinding machine.
2. When compared to a grinding machine, a CNC lathe has more machining flexibility and boasts faster tool changes.
3. CNC lathes take up less floor space than grinders and do not need flume systems.
4. PCBN tools have low-maintenance requirements.
5. PCBN inserts can produce an equal or better surface finish than grinding, while at the same time having a higher removal rate. (Results depend on the right combination of feedrate, insert nose radii and workpiece material.)
6. The structure of many PCBN grades permits for productive machining in difficult conditions, including interrupted cuts, and typically does not require the use of coolant, which keeps costs down.
7. Tool maintenance is simplified as PCBN tools may be quickly indexed to a new edge or removed and replaced with new inserts, and do not require truing or dressing to maintain the cutting profile.
8. PCBN tool inserts, combined with a plunge turning technique, produce as good or better tolerances than conventional grinding. (Plunge turning uses the entire cutting edge or a portion of the cutting edge to create an orthogonal cut. This process can reduce machining time by as much as 90 percent, producing parts with comparable surface integrity to those that are ground.)

For years, PCBN cutting tools were not a top choice among manufacturers because of their high costs, which can be up to 20 times more than conventional solutions. However, manufacturers now realize that PCBN tools make perfect economic sense in hard turning finishing operations because of their amazing efficiencies in terms of overall productivity and tool life.

If hard turning is something you’re considering for your finishing operations, Seco makes a variety of PCBN cutting tools well suited for such a purpose. Highly notable are our new CBN060K, CBN100 and CBN300 grades because they are the only solid PCBN inserts specifically developed for machining hard steel.

Similar to conventional carbide inserts, these solid PCBN inserts make use of all of their edges, which are longer than common PCBN inserts. In a study comparing these solid PCBN inserts to various tipped inserts from five different cutting tool manufacturers, cost-per-edge savings ranged between 25 and 208 percent. As an added advantage, the solid CBN060K and CBN100 grades make plunge turning possible for two reasons, properties of the grades and long usable cutting edges.

Hard turning has definitely gained momentum over conventional finishing methods and become more widely recognized as a step up in both productivity and cost effectiveness. And as an increasing number of manufacturers continue to embrace PCBN hard turning, the economic benefits will continue to add up.

About the Author

Chad manages Seco's advanced materials product lines, including all CBN and PCD products. When he's not helping customers implement advanced metalcutting solutions, you can find him training for and running 5K, 10K and 1/2 marathon races and triathlons. Chad can be reached at cmiller@secotools.com.