Surface Grinding

Surface grinding creates very flat, parallel surfaces with tight tolerances and fine finishes on mostly planar faces, often as a post-machining or post-heat-treat operation.

Overview

Surface grinding (flat grinding) uses a rotating abrasive wheel to remove small amounts of material and produce very flat, parallel surfaces with controlled thickness and surface finish. Parts are usually held on a magnetic or vacuum chuck and passed under the wheel in a controlled pattern.

You use surface grinding when you need tight flatness, parallelism, and thickness control on steels or other hard materials, often after heat treatment or rough machining. It excels at achieving fine surface finishes (e.g., Ra 8–32 µin) and correcting distortion from earlier processes. It is slower and more costly than conventional milling for bulk removal and is limited to accessible, mostly planar faces. Large interrupted cuts, flimsy parts, or parts without good fixturing surfaces are harder to grind accurately and safely.

Expect surface grinding as a finishing step for precision components rather than a primary shaping process. It fits low to medium volumes where part accuracy and finish justify the extra setup and cycle time.

Common Materials

  • Tool steel A2
  • Tool steel D2
  • Mild steel 1018
  • Stainless steel 304
  • Stainless steel 17-4PH
  • Carbide

Tolerances

±0.0005"

Applications

  • Die and mold plates
  • Shim packs and spacers
  • Machine ways and slide surfaces
  • Gauge blocks and precision parallels
  • Punch and die faces
  • Precision wear plates

When to Choose Surface Grinding

Choose surface grinding when you need very flat, parallel surfaces, controlled thickness, or fine finishes on mostly planar faces. It is ideal as a finishing step on hardened or distortion-prone parts where milling cannot economically hit the required flatness or surface finish.

vs ID Grinding

Choose surface grinding instead of ID grinding when your critical surfaces are external and flat, not internal bores. Use it to control plate thickness, flatness, and parallelism, then use ID grinding only on the specific internal diameters that need bore geometry and finish.

vs OD Grinding

Choose surface grinding over OD grinding when the key requirement is flat or parallel faces rather than precise cylindrical diameters. Use it to true up faces, control part thickness, and improve bearing or mounting surfaces that interface as flat planes instead of shafts or journals.

vs Centerless Grinding

Choose surface grinding instead of centerless grinding when you have discrete flat parts, plates, or blocks that cannot be supported and driven as cylindrical workpieces. Surface grinding gives better control of flatness and parallelism on faces, while centerless focuses on roundness and diameter on through-fed cylindrical parts.

vs CNC machining

Choose surface grinding after CNC machining when you need tighter flatness, parallelism, or finish than milling or turning can practically deliver. Rough-machine the part on a CNC to near-net shape, leave a small, uniform stock allowance, then surface grind critical faces to final dimension and finish.

Design Considerations

  • Provide a continuous, reasonably large contact area for the magnetic or vacuum chuck; avoid tiny pads or heavily pocketed surfaces as the only clamping area
  • Leave uniform grind stock, typically 0.003–0.010" per face, to clean up after heat treat or machining without chasing low spots
  • Avoid tall, thin walls or long overhangs that can deflect or vibrate under grinding pressure; add temporary supports or tabs if necessary
  • Specify surface finish and flatness only as tight as functionally needed; overly aggressive specs drive wheel choice, cycle time, and cost
  • Call out datum faces that will be ground and make sure they are accessible in a stable setup; avoid requiring multiple flips for critical relationships when possible
  • Flag sensitive materials (e.g., thin sections, air-hardened steels) so the shop can manage heat input and prevent grinding burn or warping