When I was first setting up a home machine shop, my first purchase was my venerable 12.5" x 30" Cincinnati TrayTop lathe. "Only" 1800 lbs, child's play to the experienced machinist who helped me assess it and then move it. It needed a good bit of work, both cleaning and repairing, so at first it stayed on the rather dubious wheeled supports that it was on when I bought it. By this point, my machinist friend had showed me how easy it was to jack up an end with a plain old bottle jack in order to put cribbing under it.
I failed to consider two things: first was that what he showed me involved very small vertical movements at a time, followed by the cribbing, before another incremental movement. Second was that, when he was helping me move it around, we had removed the motor, which hangs out off the back.
So when I was moving the lathe into final position, I attempted to jack it up enough to remove the wheeled base all at once. No problem on the tailstock end, so my confidence was high as I started on the headstock end. Only to see the lathe begin to tilt backward as it was a bit unbalanced on the bottle jack. As I was starting to scramble to get away -- I was not well-positioned for a quick exit, which was a point of learning of its own! -- it came to rest, with the knob that adjusts the taper fixture punching through the drywall, but coming to rest on the outside wall. After I recovered from sheer terror, I thought very, very carefully about whether I could safely redeem the situation. I decided to give it a try, and carefully pulled - and the lathe tilted back upright as easy as pie. I got very, very lucky - it was right at the point of balance. Any further, and it would have been a goner, and/or I might have been caught in the fall.
