My old shop foreman's feed rate advice cost me a ruined part yesterday

Jim, the guy who trained me 8 years ago in Dayton, always said run aluminum at 0.004 per tooth no matter what. I trusted that for years, but yesterday I was cutting a thin wall pocket on a 6061 job and it started chattering bad. I backed the feed down to 0.002 and the finish came out clean, so Jim's rule was way too aggressive for that setup. Has anyone else found that old-school tips need adjusting once you're on newer machines or tricky geometries?

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jackson.jenny1mo ago

That "0.004 per tooth no matter what" thing is exactly the trap I fell into too. Ran that number for years on open cuts and it was fine, then I tried it on a thin wall bracket and the part sang like a bird and left chatter marks all over. What worked for me was dropping the feed and also bumping the rpm up a bit, plus taking lighter depth passes so the wall had less force pushing on it. Sometimes the wall just can't take the same chipload as a solid block, the tool pushes it away and it springs back. I also started leaving a little more stock for a finish pass, that alone cleaned up most of my chatter problems. Old numbers are a decent starting point but they came from heavier old machines and simple parts, tricky shapes need their own recipe.

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