OD Grinding

OD grinding finishes external cylindrical surfaces to tight size, roundness, and surface finish on shafts and journals, often on hardened materials and precision wear surfaces.

Overview

OD grinding (external cylindrical grinding) uses an abrasive wheel to finish the outside diameter of round parts to very tight size, roundness, and surface-finish requirements. The part is usually held between centers or in a chuck and rotated while the grinding wheel traverses along the length. Shops routinely use OD grinding as a finishing step after heat treat or hardening when turning can’t hit the required accuracy or surface quality.

Choose OD grinding for shafts, journals, and precision diameters where you need low runout, good cylindricity, and fine finishes in hard or abrasive materials. It excels on moderate volumes and repeat work where setup can be reused. Compared to more general machining, OD grinding is slower and less flexible for complex features, and it requires good fixturing and access to the surfaces being ground. Expect higher per-part cost than basic turning, but better geometry control, improved surface integrity, and longer component life in bearings, seals, and sliding or rotating interfaces.

Common Materials

  • Tool steel A2
  • Tool steel D2
  • Alloy steel 4140 (hardened)
  • Stainless steel 17-4PH
  • Inconel 718
  • Tungsten carbide

Tolerances

±0.0002" to ±0.0005"

Applications

  • Bearing and seal journals on shafts
  • Hydraulic cylinder rods and piston rods
  • Motor and gearbox shafts
  • Rollers and printer drums
  • Precision dowel pins and mandrels
  • Punches and tooling shanks

When to Choose OD Grinding

Use OD grinding when you need very accurate outside diameters, roundness, and surface finish on cylindrical parts, especially after heat treat. It’s ideal for shafts, journals, and wear surfaces where runout and fit directly affect bearing life, sealing, or alignment. Best suited for small to medium batch sizes where precision and repeatability matter more than raw material removal rate.

vs Surface Grinding

Choose OD grinding over surface grinding when the critical features are external diameters, roundness, and runout on cylindrical parts, not flat faces. OD grinding can control concentricity between multiple diameters and shoulders on a shaft, which surface grinding cannot address effectively on round parts.

vs ID Grinding

Choose OD grinding instead of ID grinding when the functional surfaces are on the outside of the part rather than internal bores. OD grinding setups more easily control relationships between multiple outside diameters and faces, while ID grinding is reserved for precision bores and internal features.

vs Centerless Grinding

Choose OD grinding over centerless grinding when you need tight control of shoulders, faces, and specific datum relationships between multiple diameters. OD grinding is better for shorter runs, complex geometries, and parts that need to run between centers or in a chuck, while centerless shines on high-volume, simple, through-feed diameters.

vs CNC Turning

Choose OD grinding instead of CNC turning when the part is hardened, requires superior roundness and surface finish, or needs diameter tolerances tighter than typical turning can hold. OD grinding is slower, but it delivers better geometry and finish on critical bearing, seal, or alignment surfaces, especially post-heat-treat.

Design Considerations

  • Provide center holes or accurate datum surfaces so the grinder can run the part between centers and control concentricity
  • Leave consistent grind stock (typically 0.005"–0.015" per diameter) after turning or heat treat to clean up distortion without excessive grind time
  • Avoid very long, slender shafts without support; keep length-to-diameter ratios reasonable or plan for steady rests and support features
  • Call out which diameters, shoulders, and faces are datums so the shop can fixture and grind in the correct sequence
  • Use relief grooves and adequate corner radii at shoulders to allow the grinding wheel to reach full diameter without leaving fillets or undercut issues
  • Specify surface finish and diameter tolerance separately, and mark only truly critical features as tight-tolerance to control cost