Pro tip: I ran my finish passes way too slow for two years and didn't catch it until a chip showed up
I always thought slower feed on the last pass meant a better surface, so I was crawling at 8 IPM on 6061 for maybe 6 months straight. A guy running the lathe next to me asked why my parts were taking so long and pointed out I was rubbing instead of cutting, which was burning up inserts and leaving a dull finish. Bumped it up to 25 and the finish got cleaner, so how do you all figure out where that line actually is on a new machine?