Almost lost a finger on a Haas last month... be careful with soft jaws

I was running a job at a shop in Phoenix 3 years ago, doing some aluminum parts with soft jaws I cut myself. Last month I got a new machine and thought I'd reuse those same jaws without rechecking the grip. Took a face cut at 1500 rpm and one of the parts shot out like a bullet... hit the shield hard. I had the coolant off and was looking close to see the finish, real close. If that thing came through I'd have a busted face or worse. Anyone else had soft jaws slip on them? What wall thickness do you leave so your jaws actually hold?

1 comments

1 Comment

lisa_jones214d ago

I remember reading a thread on Practical Machinist a while back where a guy had a similar thing happen with some reused aluminum soft jaws on a lathe. Someone in the comments broke it down that if your wall thickness on the jaw is under a quarter inch, the aluminum just flexes too much under pressure and loses grip. I started leaving at least 0.3 inches of wall on my soft jaws after that, and it's made a huge difference in how solid the parts stay. Also, I always take a light pass on the jaws themselves to recut the grip profile if I'm reusing them for a second run.