OD Grinding

OD grinding finishes external cylindrical surfaces with a rotating abrasive wheel, delivering very tight diameter, roundness, and surface finish on hardened or difficult materials.

Overview

OD grinding (external grinding) removes small amounts of material from the outside diameter of a rotating part using an abrasive wheel. It’s used to hit tight size, roundness, and surface finish on shafts and other cylindrical features, often after heat treat. Typical setups are between-centers or chuck/collet, with steady rests for long, slender parts.

Choose OD grinding when turning can’t hold the required tolerance or finish, when the material is hardened, or when you need consistent bearing fits across batches. It’s common as a final operation after rough machining.

Tradeoffs: stock removal rates are low, so it’s not cost-effective for heavy material removal. Parts need a grindable, continuous OD and rigid workholding; interrupted cuts, thin walls, and extreme L/D ratios increase risk of chatter and burn. Wheel selection, coolant, and dressing drive cycle time and quality.

Common Materials

  • A2 tool steel
  • 4140 steel
  • 52100 bearing steel
  • 17-4 PH stainless
  • Inconel 718
  • Aluminum 6061

Tolerances

±0.0002"

Applications

  • Bearing journals on shafts
  • Hydraulic cylinder rods
  • Motor and pump shafts
  • Dowel pins and precision pins
  • Valve stems
  • Spindle and arbor diameters

When to Choose OD Grinding

OD grinding fits parts with critical external diameters where size, roundness, and finish drive function (bearings, seals, fits). It’s a good choice for hardened materials and for final sizing after heat treat, plating under/over-size control, or rough machining. Best for low to medium volumes where setup can be amortized and repeatability matters.

vs Surface Grinding

Choose OD grinding when the critical feature is a cylindrical OD requiring control of diameter, roundness, and runout to a datum axis. Surface grinding is better suited to flatness and parallelism on planar faces rather than precision rotational geometry.

vs ID Grinding

Choose OD grinding when the controlled feature is the outside diameter or when the bore is not accessible or not the functional interface. ID grinding targets internal diameters and is typically driven by bore size, taper, and internal finish requirements.

vs Centerless Grinding

Choose OD grinding when you need datuming to centers or a specific feature for concentricity/runout control, or when the part geometry includes shoulders, steps, or features that complicate centerless feeding. Centerless grinding excels on long runs of simple cylinders but offers less direct control to a defined datum axis.

Design Considerations

  • Call out the datum scheme (centers, chuck, or a reference journal) and specify TIR/runout requirements explicitly
  • Provide usable center holes if between-centers grinding is required; protect centers through heat treat and handling
  • Limit interrupted ODs, keyways, and cross-holes in the grind zone or expect slower cycles and higher risk of burn/chatter
  • Leave appropriate grind stock after turning (commonly 0.005–0.020 in on diameter depending on size and condition) and specify whether material is hardened
  • Avoid thin-walled sections at the grind diameter; add support journals or allow use of steady rests for high L/D parts
  • Specify surface finish and any geometry tolerances (roundness/cylindricity/taper) only as tight as function demands to control cost