Chasing a chatter on a 4140 shaft that turned out to be one loose insert

Spent most of Tuesday chasing a chatter on a 4140 shaft that showed up around 900 rpm in the finish pass, and I mean I tried everything, speeds, feeds, a new collet, even re-indicated the vise twice. Turned out insert number 3 on the face mill was sitting about half a turn loose, which I found by pure luck when I bumped the holder with my knuckle during a coolant change. Twelve years on machines and one loose screw still ate four hours of my day and a fresh end mill I didn't need to change. How do you guys check inserts before a run without pulling the whole cutter apart?

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mark_ward5h ago

Wouldn't a torque wrench on every insert before the run have caught that in five minutes?

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