Automotive Hub Unit Hardened Steel Finishing: CBN Inserts Improve Consistency and Tool Life

Production Validation: Competitive Tooling Comparison

Project Background and Machining Challenge

The raceway is a critical finishing area of an automotive hub unit. For 65Mn hardened to HRC 62, the process requires stable wear resistance, reliable edge performance and controlled cutting behavior. In this application, the finishing allowance was approximately 0.15 mm, making the process sensitive to surface marks, dimensional variation and progressive tool wear.

The customer also needed a tooling solution suited to an automated production line. Frequent insert changes could interrupt the machining rhythm, while inconsistent tool performance could make long-run dimensional control more difficult. The goal was to support hard turning as an efficient alternative to greater reliance on grinding, without changing the established 52-second cycle time.

UHD CBN Insert Solution

UHD selected the UPN306C05 CBN grade in VNGA160408 geometry for continuous dry finishing of the hub unit raceway. The solution was matched to the existing cutting conditions of Vc 207 m/min, ap 0.15 mm and f 0.14 mm/r. This approach focused on stable small-depth material removal, consistent surface generation and predictable tool wear during continuous machining.

Application Value

• Maintained the same 52-second machining cycle as the comparison tooling.
• Extended validated tool life from 100 to 130 pieces per cutting edge, reducing the frequency of tool changes.
• Helped reduce surface variation and support more consistent raceway finishing during continuous production.
• Improved tooling stability for automated operations, supporting smoother production flow and less manual intervention.
• Provided a practical reference for similar hardened steel finishing applications, including bearings, gears and transmission components.