Precision grinding from independent shops
Abrasive grinding holds the tightest tolerances and finest surface finishes of any machining process, including on hardened materials that milling and turning cannot touch after heat treat. Upload a part or print and hear back from shops set up for grinding.
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How OpenSpindle works
We tap our partner network. You get the best-match quote.
Upload your part and we tap our network of partner shops to get you a competitive, all-in quote that is the best match for the job.
One upload
A CAD file or a sketch. That is the whole ask on your end.
Your best-match quote
Sourced from the partner shops set up for your exact part.
All-in, on your timeline
Machining, finishing, and shipping detailed to your turnaround.
Design rules
How to design for Precision Grinding
Grinding uses a spinning abrasive wheel to remove a small, controlled amount of stock, which is why it holds tolerances and finishes that milling and turning cannot.
| Design rule | Typical spec | Why |
|---|---|---|
| Achievable tolerance | to ~±0.0001 in (0.0025 mm) | Light abrasive cuts and stiff machine setups hold tenths where milling and turning cannot. |
| Surface finish | to ~4-8 µin Ra | Fine wheel grits and slow finishing passes produce a mirror-like surface. |
| Flatness / parallelism | to ~0.0002 in | Surface grinding is the standard way to true two faces flat and parallel. |
| Hardened material capability | grinds hardened steel, carbide, ceramics | Abrasive cutting removes material regardless of hardness, unlike a single-point tool. |
| Grind stock allowance | leave ~0.005-0.015 in for grinding | Rough the part close on a mill or lathe first, then leave finish stock for the grinder to clean up. |
Typical starting points; a shop confirms against your part, material, and hardness.
Process comparison
Precision grinding vs other processes
When another process fits better than grinding.
| Process | Best for | Typical volume | Choose it over Precision Grinding when |
|---|---|---|---|
| CNC Machining | General tolerances, soft or as-machined finish | Prototype to production | A milled or turned finish and tolerance suffice, typically before heat treat. |
| EDM & Wire EDM | Complex hard-metal detail, internal features | Prototype to production | The part needs sharp internal detail in hardened material with no cutting force. |
| Lapping and honing | The final finish on flats and bores | Low to production | The part needs the ultimate flatness or bore finish beyond what grinding alone leaves. |
Get a better quote
Getting a quote that comes back fast
| Instead of | Send this |
|---|---|
| "Ground part, need a quote" | "4140 steel, hardened 50 HRC, surface grind top face flat and parallel to 0.0002 in, qty 10" |
| "Needs to be round and precise" | "O1 tool steel shaft, cylindrical grind ⌀0.500 in ±0.0002, 8 µin Ra finish" |
| "Lots of small pins, tight tolerance" | "303 stainless dowel pins, centerless grind ⌀0.125 in ±0.0002, qty 2,000" |
Say the material and hardness, the surface being ground, and the tolerance and finish that matter. Grinding is often called out for one critical feature, not the whole part.
Applications
Industries we serve
Grinding shops on OpenSpindle finish hardened tooling, shafts, gauges, and precision components for demanding industries, including AS9100 and ISO 13485 shops.
More on OpenSpindle
Need a different process?
Get a quote for these capabilities too.
Designing for this process
What actually changes your quote
Not a definition of grinding. The design choices that move your price and lead time.
Surface grinding trues flats
A surface grinder holds a part on a magnetic chuck and passes a wheel over the top face, the go-to way to make two faces flat and parallel after heat treat or welding distortion.
Cylindrical grinding finishes round features
A part turns between centers or in a chuck while the wheel grinds an outside diameter, shoulder, or taper to final size, common for shafts, pins, and rollers.
Centerless grinding suits volume round parts
Parts feed between two wheels with no chuck or centers needed, which removes setup time per part and makes it economical for grinding large batches of pins and shafts to a consistent diameter.
Call out only the features that need it
Grinding is slower and pricier per surface than milling or turning. Spec grinding for the one or two features that carry the tight tolerance or finish, and leave the rest at a standard machined tolerance.
Questions
Frequently asked questions
Precision grinding uses a spinning abrasive wheel to remove a thin, controlled layer of material, holding tolerances and surface finishes tighter than milling or turning. It is the standard way to finish a part after heat treat, when hardening has thrown off dimensions that only an abrasive process can correct.
Get precision grinding quotes
Upload a part or print and compare quotes from independent shops set up for surface, cylindrical, and centerless grinding.
STEP · STL · IGES · DWG · DXF · PDF · and more
Uploads are secure & confidential