Centerless Grinding

Centerless grinding grinds external cylindrical diameters without centers, delivering high throughput, excellent roundness, and tight size control on long or small parts.

Overview

Centerless grinding removes material from an OD while the part is supported by a regulating wheel and work rest blade, not between centers. It runs as thru-feed for continuous parts (pins, rods, tubes) or infeed/plunge for parts with shoulders or specific ground bands. Typical results include excellent roundness, straightness, and surface finish with very high production rates.

Choose it for simple cylindrical geometry where you need consistent diameter control across volume—especially small, slender, or hard-to-hold parts that would deflect or chatter in chucks/centers. It’s common after heat treat for bearing and shaft components.

Tradeoffs: geometry is constrained (no keyways/slots, limited interrupt), and “non-round” or complex profiles aren’t a fit. Setup and process development (blade height, wheel specs, regulating speed) drive lead time and cost, so it pays off most in repeat work and moderate-to-high quantities.

Common Materials

  • 52100 Bearing Steel
  • 4140 Steel
  • 17-4 PH Stainless
  • 303 Stainless
  • A2 Tool Steel
  • Inconel 718

Tolerances

±0.0002"

Applications

  • Dowel pins
  • Bearing rollers and races (OD)
  • Hydraulic piston rods
  • Motor shafts
  • Medical guide wires
  • Pump shafts

When to Choose Centerless Grinding

Pick centerless grinding for high-repeat OD work where diameter, roundness, and finish matter and the part can be fed or plunged without complex fixturing. It fits best for long, slender, or small-diameter parts and for post-heat-treat sizing. It’s most economical when you have enough volume to amortize setup and wheel development.

vs Surface Grinding

Choose centerless grinding when the critical feature is an OD diameter and roundness on a cylindrical part, especially in volume. It avoids part-to-part locating and clamping errors that show up when trying to hold small round parts for flat grinding.

vs ID Grinding

Choose centerless grinding when the requirement is external size control and you don’t need internal bore geometry corrected. It’s faster and simpler for OD sizing because it avoids bore workholding and internal wheel access limits.

vs OD Grinding

Choose centerless grinding when you want higher throughput on straight cylindrical ODs or when the part is too slender to run between centers or in a chuck without deflection. OD grinding is often better when you must reference a specific center, grind tapers, or control features relative to centers.

Design Considerations

  • Specify the functional reference for the OD (free-state OD vs OD relative to a bore/face) so the shop can choose the right process and inspection method
  • Keep the ground OD continuous when possible; interruptions, flats, and heavy cross-holes increase cycle time and can affect roundness
  • Provide adequate lead-in/lead-out lengths for thru-feed parts and avoid tiny ground bands that force infeed-only setups
  • Call out realistic total indicator runout/roundness requirements; separate size tolerance from form/finish requirements
  • Define stock condition and stock allowance (e.g., pre-turned, heat treated) so wheel selection and cycle time are predictable
  • Avoid sharp shoulders at the grind boundary; add small reliefs or radii to reduce burning and wheel wear