I finally figured out why my parts kept drifting 0.003, and it was not the machine

Finley Carr · 2026-10-07T05:35:04.143488+00:00

Last Tuesday I ran a batch of 60 aluminum brackets on the old Haas VF2 and every single one came out 0.003 over on the width. I checked the program twice, touched off the tool again, even swapped the end mill for a fresh one. Nothing. Then Rick, the guy who has run that machine since before I started, walked over and asked when I last cleaned the vise jaws. I told him maybe two weeks back. He pulled a chip the size of a rice grain out of the corner of the jaw with his fingernail. That tiny piece of swarf was cocking the whole part up in the vise. After I pulled the jaws and stoned them flat, the next 60 parts all hit within 0.0005. Two weeks of chasing ghosts over one chip I could not even see without kneeling down. Now I blow the jaws out before every setup, no exceptions. What is the dumbest little thing that has thrown your tolerances off?

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I finally figured out why my parts kept drifting 0.003, and it was not the machine | CNC Operators - HW Forums