---
title: "Precision Grinding Services | Surface & Cylindrical | OpenSpindle"
description: "Get quotes for surface, cylindrical, and centerless grinding from independent machine shops. Abrasive grinding holds the tightest tolerances and finest finishes, even on hardened materials. Upload a print."
canonical: https://openspindle.com/capabilities/precision-grinding
---

# 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.

## Grinding shops on OpenSpindle

Real shops running surface, cylindrical, and centerless grinders for tight-tolerance and hardened parts. See their equipment and get a competitive quote for your project.

[Browse all grinding shops](https://openspindle.com/manufacturers?capability=Grinding)

## 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.

## 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](https://openspindle.com/capabilities/cnc-machining.md) | 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](https://openspindle.com/capabilities/edm.md) | 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. |

## What Makes a Good RFQ

| Instead of | Send |
| --- | --- |
| "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.

## Industries Served

- Aerospace & defense
- Medical devices
- Automotive
- Industrial / OEM
- Tool & die

Grinding shops on OpenSpindle finish hardened tooling, shafts, gauges, and precision components for demanding industries, including AS9100 and ISO 13485 shops.

## Frequently Asked Questions

### What is precision grinding?

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.

### What is the difference between surface, cylindrical, and centerless grinding?

Surface grinding flattens and finishes a face, typically on a magnetic chuck, and is used to true up flat and parallel surfaces. Cylindrical grinding rotates a part between centers or in a chuck to grind an outside diameter, shoulder, or taper round and to size. Centerless grinding feeds round parts between two wheels with no chuck or centers, which makes it fast and economical for grinding large quantities of shafts or pins to a consistent diameter.

### What tolerance and surface finish is achievable with grinding?

Surface and cylindrical grinding commonly hold tolerances to about ±0.0001 in and surface finishes down to roughly 4-8 µin Ra, well beyond what a mill or lathe alone can hold.

### Can you grind hardened steel?

Yes. Grinding is the standard finishing process for hardened tool steel, carbide, and ceramics, since abrasive cutting removes material regardless of hardness while a single-point cutting tool cannot. Most hardened parts are ground after heat treat to bring dimensions back into tolerance.

### How much stock should I leave for grinding?

A common allowance is 0.005-0.015 in per surface, roughed close on a mill or lathe before heat treat, then removed by the grinder afterward to true up size and finish.

### What file formats should I send?

STEP, IGES, X_T, DWG, DXF, or a dimensioned PDF. Include material and hardness, the surface or feature being ground, its tolerance and finish, and quantity.

## Other Capabilities

- [CNC Machining](https://openspindle.com/capabilities/cnc-machining.md)
- [CNC Turning](https://openspindle.com/capabilities/cnc-turning.md)
- [EDM & Wire EDM](https://openspindle.com/capabilities/edm.md)

## Design Notes That Move Your Price

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.

## Get precision grinding quotes

Upload a part or print and compare quotes from independent shops set up for surface, cylindrical, and centerless grinding.