Old timer told me to run my endmill 3x slower, I laughed until I tried it

Guy who's been running Bridgeports since the 70s said my chatter was from speed, not depth. Dropped from 8k to 2500 rpm on a 1/4" tool in 6061 and the finish came out like glass. Anyone else get advice that contradicted everything in the manual?

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claire_walker23d ago

Wait, 8k down to 2500 on a quarter inch tool in 6061 and it didn't just rub or break? That's like half the speed the chart says for HSS, let alone carbide. I mean, I've pushed feeds and sped things up to beat chatter, but going the other way never even crossed my mind. That old timer must have some sixth sense for harmonics or something, because my brain says that should've been a disaster. But if you got a mirror finish, I gotta try it on my next stuck job, even if it feels wrong the whole time.