Machining and cutting
Grinding: what goes wrong and where to inspect
Grinding finishes hardened or precision parts to tight tolerances and fine surface finish: bearing seats, shafts, pins, valve seats and gauge faces.
01How the process works
An abrasive wheel removes small amounts of material at high speed. Cylindrical, internal, centreless and surface grinding cover most part types. Dressing restores the wheel profile, and coolant controls heat.
The main hidden risk is grinding burn: local overheating that tempers or rehardens the surface, invisible to the eye but harmful to fatigue life. It is detected by nital etch or Barkhausen noise testing. Roundness and surface texture need suitable instruments, not only micrometers.
- Pre-machined and hardened part. Stock allowance and hardness verified.
- Set-up and dressing. Wheel dressed, machine set.
- Grinding. Roughing and spark-out cycles.
- In-process gauging. Size controlled by gauges.
- Inspection. Size, roundness, roughness, burn check.
02What typically goes wrong
| Defect | Typical cause | How it is found |
|---|---|---|
| Grinding burn | Excess heat, worn wheel, coolant | Nital etch, Barkhausen |
| Grinding cracks | Overheating on hardened steel | MT |
| Out of roundness and lobing | Centreless set-up, vibration | Roundness tester |
| Taper | Machine alignment | Micrometer at several positions |
| Chatter marks | Wheel balance, vibration | Visual, roughness |
| Size drift | Wheel wear, temperature | SPC |
03Where an inspector should look
Before production
- Hardness and allowance of incoming parts
- Burn check method agreed
- Gauge calibration
During production
- Dressing frequency
- Coolant condition
- SPC of size
After production
- Roundness and roughness
- Burn inspection on samples
- Corrosion protection
04Standards and references
ISO 14104 (nital etch for grinding burn), ISO 12181 (roundness), ISO 21920 (surface texture).
Standards are named for orientation. The applicable edition and acceptance criteria are those in your contract and specification.