Hardened Shaft Bearing Journal – Case Study

Hardened Shaft Bearing Journal

The Challenge

This customer was manufacturing alloy steel hardened shaft bearing journals using a Pittler vertical CNC lathe with the axle mounted on the rotary table. The shaft hardness had to be 52-55 HRc, and a surface finish of less than 16 Ra microinches (0.4 Ra). Before they turned to us for suggestions, here was their pre-op process:

Turning Operation prior to burnishing:

  • Material heat treated to 52-55 HRc
  • Finished turn using carbide insert with a .03” (0.8mm) nose radius
  • Speed: 300 RPM
  • Cutting feed: 0.006” per rev (0.15mm/rev)
  • Achieved finish: 32-40 Ra microinch (0.8-1.0 Ra)

Our Solution

After the customer contacted us, we suggested using a special diamond burnishing tool made by Elliott Tool Technologies. Here were the statistics for the new burnishing solution:

  • Speed: 300 RPM
  • Cutting feed: 0.002” per rev (0.05mm/rev)
  • Radial displacement: 0.01” (0.3mm)
  • Finish achieved: 9 -12 Ra microinch (0.22-0.30 Ra)

Final Results

The special diamond burnishing tool produced the desired surface finish of less than 16 Ra microinch (0.4 Ra). The tool saved our customer from having to purchase an expensive grinding machine, saving them $130,000. The tool also allowed them to keep the process in one setup, saving a lot of time and energy.