Surface Grinding

Surface grinding produces flat, parallel, and square faces with tight size control and fine finishes using an abrasive wheel on a reciprocating or rotary table.

Overview

Surface grinding (flat grinding) removes small amounts of material with an abrasive wheel to generate highly flat, parallel, and square surfaces. Shops commonly use it after heat treat or rough machining to hit final thickness, improve flatness, and achieve consistent surface finish across a face. Typical machines include reciprocating-table and rotary-table grinders, often with magnetic chucks for ferrous parts.

Choose surface grinding for precision planar geometry: plates, spacers, mold inserts, and datum faces that need tight thickness control and low waviness. It’s best for parts with good workholding surfaces and enough stock to grind (often 0.001–0.010 in depending on material and condition).

Tradeoffs: it’s not efficient for heavy stock removal, deep pockets, or complex 3D forms. Non-magnetic materials need alternate fixturing, and thin parts can distort from clamping or grinding heat. Sharp edges are prone to burrs or burn; reliefs and controlled stock allowance reduce risk.

Common Materials

  • A2 tool steel
  • D2 tool steel
  • 4140 steel
  • 304 stainless steel
  • 17-4 PH stainless steel
  • Aluminum 6061

Tolerances

±0.0005"

Applications

  • Ground spacers and shims
  • Mold and die plates/inserts
  • Precision fixture and gauge plates
  • Machine way components and wear strips
  • Valve and pump sealing faces
  • Knife and shear blades

When to Choose Surface Grinding

Surface grinding fits parts that primarily need accurate thickness, flatness, and parallelism on one or more faces with a consistent finish. It’s a strong choice for low-to-medium quantities where controlled material removal after heat treat or rough machining is required. Parts should have stable geometry and a clear workholding plan (magnetic, vacuum, or mechanical).

vs ID Grinding

Choose surface grinding when the critical features are flat faces (thickness, flatness, parallelism) rather than precision internal diameters. Surface grinding is typically simpler to fixture for planar datums and can finish large contact areas uniformly. If the functional requirement is bore size/roundness/concentricity, ID grinding is the better match.

vs OD Grinding

Choose surface grinding when you need accurate planar datums or thickness control instead of precise external diameters. It excels at producing square, flat faces that control stack-up in assemblies and provide reliable locating surfaces. If the part’s critical features are cylindrical ODs with tight roundness and size, OD grinding is more appropriate.

vs Centerless Grinding

Choose surface grinding for parts defined by flat geometry, or when you need a controlled reference face before other operations. Centerless grinding is optimized for high-throughput, tight-diameter parts with long lengths and consistent OD stock. For short runs, mixed geometries, or thickness/flatness requirements, surface grinding is usually the more direct approach.

vs CNC milling

Choose surface grinding when you need better flatness, parallelism, or surface finish than typical milling can hold on hardened materials or thin sections. Grinding also minimizes tool deflection and can hold tight thickness across a broad face. For complex 3D features or heavy stock removal, milling is usually more efficient before grinding to finish.

Design Considerations

  • Specify which faces are grind-critical and give a realistic stock allowance per face (commonly 0.001–0.010 in)
  • Add small edge breaks or reliefs to reduce burrs, chipping, and burning on sharp corners
  • Provide a flat, stable surface for workholding; plan for non-magnetic fixturing if using aluminum or austenitic stainless
  • Avoid very thin, wide plates without a distortion plan; call out flatness requirements and let the shop choose clamping strategy
  • Call out surface finish (Ra) and flatness/parallelism separately; don’t assume a size tolerance guarantees geometry
  • Leave room for wheel clearance near shoulders or steps; add undercuts/reliefs if a face must grind to a wall