That moment a collet let go and my part became a projectile

I was running a job on our old Haas Mini Mill last Thursday when a 1/2 inch end mill pulled out of the collet and shot across the shop, barely missing my forearm. After that, I spent the rest of my shift double-checking every single collet nut torque. Has anyone else had a near miss like that and changed your setup routine after?

2 comments

2 Comments

scott.grace1d ago

100 bucks says it wasn't just the torque but the collet itself. I've seen cheap split collets get work-hardened and lose their grip way before the nut ever backs off.

davis.keith1d ago

My buddy Dave had a 3/8 carbide end mill come flying out on a VF-2 last year, bounced off the enclosure door and put a dent in the chip auger cover. He told me that was the day he switched from impact drivers to a torque wrench for every single collet nut on his setup. Now he even marks each nut with a paint dot after torquing so he can see if anything moved during a long run.