I was turning and threading one end of a shaft in an old Bridgeport EZ Path CNC lathe. The shaft was made of one inch diameter 304 stainless steel, and was about 6 feet long. To chuck near the end I was working on, that meant that I left about three feet of slender shaft hanging out of the tube. I wrote a program to do my turning at 400 RPM, before slowing the spindle for the threading. Well, I fat fingered the 400 RPM and keyed in 700 rpm instead. When I started the spindle and it climbed to 700 RPM, all hell broke loose. The machine literally started jumping up and down and bouncing all over the place. Two of the foot pads were not even under the machine when it was all over. The control is mounted on an arm that will swing around for convenience. And about the time I was reaching for the E-stop, there was a loud bang and the arm came swinging towards My face hard enough to relocate my head. I did manage to hit the e stop and drop back just in time, as the keys were launched throughout the end of the shop behind me, and the monitor came to a rest on the chuck and tool post, hanging by the wires/cables.

304 stainless is tough, but it is very flexible. The tail end of the shaft had started bending, therefore causing the machine to be extremely out of balance, and it got progressively worse quickly. In just a couple of short seconds the shaft had bent to near ninety degrees. It was this that had knocked the controller straight at Me. Imagine a three foot long piece of one inch dia. steel swinging at close to 700 RPM and hitting the control box. Scary stuff.

I guess I'm really blessed that I wasn't hurt except for a very slightly mashed finger nail. Still not sure how that happened. When I walked into the office to tell my boss about it, I was fully expecting that a few minutes later, I would be loading my tool box on my truck. I kept my job though.