Rough Patch
A localised area where the surface finish is measurably worse than the surrounding surface.
What causes it
- Tool chatter from insufficient rigidity or the wrong speed
- A worn or chipped insert part-way through a pass
- Inconsistent feed, or a pause in the cut
- Coolant starvation over part of the surface
Why human inspection misses it
Surface finish is judged by comparison, and the comparison is usually against memory or a worn reference coupon. Marginal cases get passed because the inspector cannot be certain.
How it looks to a camera
Local texture statistics can be compared against the rest of the same surface, which turns a subjective comparison into a measurement taken under identical conditions on every part.
Why it matters
Roughness outside specification affects sealing, friction, fatigue life and coating adhesion. A patch that appears part-way through a batch usually means a tool changed state mid-run.
Adam detects rough patch along with five other defect classes. Upload a photograph of your part and see what it finds.