What is Hard Turning?

What is hard turning?

Hard turning is defined as the process of single point cutting of part pieces that have hardness values over 45 Rc. Typically, however, hard turned part pieces will be found to lie within the range of 58-68 Rc. The hard turning process is similar enough to conventional “soft” turning that the introduction of this process into the normal factory environment can happen with relatively small operational changes when the proper elements have been addressed.

Hard turning is best accomplished with cutting inserts made from either CBN (Cubic Boron Nitride), Cermet or Ceramic. Since hard turning is single point cutting, a significant benefit of this process is the capability to produce contours and to generate complex forms with the inherent motion capability of modern machine tools. High quality hard turning applications do require a properly configured machine tool and the appropriate tooling. For many applications, CBN tooling will be the most dominant choice. However, Ceramic and Cermet also have roles with this process.

The range of applications for hard turning can vary widely, where at one end of the process spectrum hard turning serves as a grinding replacement process, and can also be quite effective for pre-grind preparation processes. The attractiveness of the process lies in the performance numbers. A properly configured hard turning cell would typically demonstrate the following:

• Surface finishes of 0.00011" (.003 mm)
  
• Roundness values of .000009" (.00025 mm)
  
• Size control ranges of .00020" (.005mm)
  
• Production rates of 4- 6 over comparable grinding operations

Hard turning is a technology-driven process that requires certain performance features of the machine tool, workholding, process and the tooling.