Man, and I knew better too. Decided to add a ream operation at the end of a new program, really not to run the ream operation, but to have the x and y locations and the final depth of the reamer right there in the program to keep from needing to write them down. Got it done and loaded the program and the mill head came rapid down into the top of my vise. Forgot the mandatory M03 and spindle speed prior to a G86 (my mill is manual spindle operation so never use them).
The spindle was only about an inch and a half above the vise at the time and came down so fast I couldn't react quick enough. One other thing I forgot to do was hit the reset button before I loaded the new program. You know, you think you got it all figured out after 30 or 40 programs. The first time I used a G86, the head went the other way, but had a ways to go to the top so I got it stopped. I think I'll get into two habits here, add the spindle on and speed values and a spindle stop at the end of each operation on every program, and hit the reset button before loading the new programs.
Now I have to replace the bent 3/4" ballscrew. Bent it just above where the nut was at the time, about 14 to 17 inches down from the top of the column. That is exactly where the majority of my programs have been running lately. The bend causes the head to stutter, even at low feed rates. It travels good a few inches above the bend.
Hope this keeps someone else from the same fate. At least it was the shortest ballscrew and I don't think it messed up the nut. Now I really need to finish my thread die holder for my lathe.