Precision Grinding

Hardened material.
Micron tolerance.
Surface, cylindrical, centerless.

Precision grinding finishes hardened materials to tolerances and surface finishes beyond CNC machining capability. Surface grinding for flat parts, cylindrical grinding for round parts, centerless grinding for high-volume cylindrical production.

Precision Grinding Quote Honing & lapping

±0.002 mm Ra 0.2 µm Any hardness 3 grinding types

01 · What it is

How Precision Grinding works.

Grinding uses a rotating abrasive wheel to remove small amounts of material with high precision. Each abrasive particle acts as a tiny cutting edge, removing material one chip at a time. The accumulated effect produces tight tolerances, fine surface finishes, and the ability to machine hardened materials that conventional cutting tools cannot handle.

Surface grinding: Flat table moves workpiece past rotating abrasive wheel. Produces precision flat surfaces on plates, blocks, fixtures. Tolerance ±0.005 mm flatness, Ra 0.4 µm surface finish standard.

Cylindrical grinding: Part rotates between centers while rotating wheel grinds the outside diameter. Standard for precision shafts, pins, bearing journals. ±0.002 mm diameter tolerance, Ra 0.2 µm finish.

Centerless grinding: Part held between two rotating wheels (regulating and grinding) with no center support. Ideal for high-volume cylindrical production. Thousands of parts per hour. Very precise diameter but no fixed axis reference.

02 · Specifications

Capability specs.

±0.002 mm

Tolerance

Precision grinding tolerance. ±0.001 mm achievable on selected features

Ra 0.2 µm

Surface finish

Typical ground surface finish. Ra 0.05 µm with polishing pass

0.005 mm

Flatness

Surface grinding flatness across plate surfaces

65 HRC

Max hardness

Grinding works on fully hardened material — beyond CNC cutting capability

Any material

Compatibility

Hardened tool steel, carbide, ceramic — materials CNC cannot machine

500 mm

Max cylindrical length

Cylindrical grinding capacity for shafts and pins

500 × 800 mm

Surface grinding bed

Flat surface grinding table size

High volume

Centerless production

Thousands of small cylindrical parts per hour capability

03 · Applications

Where Precision Grinding excels.

Hardened tool steel

D2, H13, A2 tool steel components after heat treatment — only grinding cuts hardened steel

Precision shafts

Motor shafts, pump shafts requiring concentric bearing journals

Pins and gauges

Precision pins, gauge pins, locating pins — ground to ±0.002 mm

Bearing races

Ball and roller bearing inner/outer races — final finish operation

Flat reference surfaces

Precision gauge blocks, reference flats, tooling plates

Mold plates

Injection mold plates after heat treatment — flat parallel surfaces

Punch & dies

Stamping punches and dies in hardened D2 — precision working surfaces

Carbide tooling

Tungsten carbide cutting tool grinding — only grinding cuts carbide

High-volume pins

Centerless grinding of dowel pins, roller pins — production quantities

04 · When not to use it

Not suitable for:

Every process has its limits. Being honest about where Precision Grinding isn\'t the right answer saves time and money.

Soft aluminum or copper — grinding wheel loads rapidly, inefficient
Large material removal — grinding removes microns, not mm per pass
Complex 3D geometry — grinding is primarily 2D flat or cylindrical
Low-quantity prismatic work — CNC milling cheaper and faster
Parts where CNC tolerance (±0.025 mm) is adequate

FAQ

Precision Grinding questions.

Three scenarios: (1) Material is harder than ~45 HRC — CNC cutting tools wear prohibitively fast. (2) Tolerance tighter than ±0.025 mm required — CNC struggles to maintain below this consistently. (3) Surface finish better than Ra 0.8 µm required — CNC finish passes can't reach Ra 0.2 µm reliably. When any of these apply, grinding is the right process.

Standard for hardened precision parts. Workflow: CNC machine to slightly oversize (leave 0.2–0.5 mm grinding stock), heat treat to required hardness, grind to final dimension. Heat treatment distorts parts (0.1–0.3% typical), so CNC to final dimension before heat treatment doesn't work. Grinding stock allows recovering final dimension after heat-treat distortion.

High volume: thousands of parts per hour for small cylindrical pins. No chucking or fixturing — parts fed continuously between wheels. Excellent diameter tolerance (±0.005 mm typical). Limitation: no reference axis — cannot grind features referenced to one end of the part. For high-volume dowel pins, roller pins, bearing rollers: centerless is unbeatable.

Yes with diamond grinding wheels. Tungsten carbide cutting tools, ceramic bearings, and even sapphire components can be precision ground with appropriate wheel selection. Cost is higher (diamond wheels expensive, slower cutting) but grinding is often the only practical process for these ultra-hard materials.

Surface grinding: $30–100 per hour plus setup. Cylindrical grinding: $40–120 per hour plus setup. Centerless grinding at production volume: $0.10–1 per part (scales with volume). For a single precision shaft, cylindrical grinding adds $30–100 to CNC cost. For production quantities, grinding cost is small relative to overall part cost and often justified by tolerance requirements.

Grinding typically adds 3–7 days to overall lead time. Surface grinding: 3–5 days. Cylindrical: 5–7 days. Centerless setup: 3–5 days then production runs fast. For rush orders, grinding can be expedited but the manual nature of setup limits how much time can be saved.