A bad surface finish usually has a recognizable cause. Match the symptom to the fix.
Symptom → fix
| Symptom | Likely cause | Fix |
|---|---|---|
| Rippled/patterned marks | Chatter (vibration) | Reduce stickout, change RPM, add rigidity |
| Coarse tool marks | Feed per tooth too high | Light finishing pass, lower feed |
| Torn/dragged surface | Dull tool or built-up edge | New/sharper tool, increase speed |
| Scalloping on contours | Stepover too large | Reduce stepover |
| Rubbing/burnishing | Feed too low | Increase feed to proper chip load |
The general approach: leave a small finishing allowance and take a dedicated light finishing pass with a sharp tool, climb milling, adequate coolant, and a rigid setup. If chatter is the problem, attack rigidity and spindle speed first.
Frequently asked questions
Why is my finish rough? Most often chatter or too-high feed per tooth — diagnose by the mark pattern.
Does slowing the feed always help? No — too low causes rubbing; aim for proper chip load.
Best single fix? A light finishing pass with a sharp tool, climb milling, on a rigid setup.
Keep a small magnifier or loupe at the machine — many finish problems are obvious once you can see the tool marks clearly, and the pattern points straight to the cause. Photographing a bad surface next to your settings also builds a reference you can learn from over time.