Ran my drills 20 percent too fast on 6061 for two shifts, and a finish cut is what called me out

Uma Murray · 2026-10-17T08:40:03.512918+00:00

For two whole shifts on a batch of 200 aluminum brackets I was running a 3-flute carbide at 8000 rpm, and the parts looked fine to me. Then I ran a light finish pass and saw chatter marks you could feel with a fingernail, plus tool life dropped from around 40 parts to 22. I pulled up the speeds and feeds chart and my surface footage was way off for 6061, I'd just copied the number from an old program and never checked it. So here's my debate: do you trust the book numbers and dial back, or do you push till the finish tells you to stop? Curious what rpm you all actually settle on for 6061 with a 1/2 inch 3-flute.

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Ran my drills 20 percent too fast on 6061 for two shifts, and a finish cut is what called me out | CNC Operators - Topic Shares