Question about running a 0.500 end mill at 8000 rpm on alum, a crash in Kokomo changed my mind

Jake Price · 2026-10-12T06:20:04.359588+00:00

Everyone on the floor at my old shop in Kokomo told me to push aluminum hard with small end mills, so I ran a 0.500 carbide at 8000 rpm and 200 ipm like they said. About 20 minutes into a run of 340 brackets, the tool snapped, spun the part out of the vise, and chewed up the back jaw of a Kurt. The foreman pulled the speeds and feeds book off the shelf and showed me I was way past the chip load the cutter was rated for, and he was right. I kept running hot after that for maybe 6 months anyway, because it worked most of the time and I liked finishing early. Then I started checking the chip color and listening to the cut instead of trusting what guys told me at break. Now I run closer to 6000 rpm and adjust off the sound, and my tool life on those same brackets went from about 3 hours to almost a full shift. Has anyone else had a crash like this right after being told to just send it?

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Question about running a 0.500 end mill at 8000 rpm on alum, a crash in Kokomo changed my mind | CNC Operators - Topic Shares