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Troubleshooting

Poor Surface Finish: Diagnose and Fix It

A rough wall or floor usually comes down to coolant, chip load, or a missing corner radius. Here's the quick diagnostic to get back to a clean finish.

Surface finish is where everything upstream shows up. A torn or hazy wall, a scalloped floor, or chatter ripple each point to a specific cause — and most are a one-knob fix. Run the checklist below before you slow the whole job down chasing finish.

Poor surface finish — causes & fixes

Cause
Fix
Not enough coolant
Add coolant or increase pressure
Chip load per tooth too high
Decrease the feed rate
RPM too high
Decrease RPM
Rough floor finish
Add a corner radius to the tool to spread the load and blend the floor
Edge chipping leaving witness marks
See the Chipping guide

Floors love a corner radius

A sharp-cornered square end mill concentrates all the cutting force on a vanishing point of edge — it leaves a poor floor and chips easily. Adding even a small corner radius spreads the load over an arc, strengthens the corner, and blends the floor finish. RobbJack offers corner radii across its end-mill lines for exactly this reason.

Walls love polished flutes

In aluminum, finish quality is dominated by how cleanly the flute releases the chip. RobbJack's polished-flute and Mirror Edge™ tools (A1-303, AL3, FM/FMHV) shed material without smearing, leaving a bright wall — and the AL3 long-reach series is built to finish a deep wall in a single pass without witness marks.

Get coolant on it, ease the feed and RPM, and put a corner radius on the tool for floors — finish problems are usually this simple.

Have a job like this?

Tell us your material and operation — our application engineers will recommend the tool and the speeds & feeds to run it.

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