My first "Real" lathe, many years ago, I had installed the 4 jaw on it and was trying to get the chuck wrench to tighten a bit more, in the process my hip hit the start lever, in reverse! Since the speed was set at the lowest gear I had time to let the wrench go, and watched it disappear over the back side followed by the wrench flying up, it had stayed in the chuck until it hit the cast iron chip pan and busted the square end right off.
That lathe had a switch lever that was about 6-8" long with the knob on top when in the off position (Takisawa TS800) where it sat in a detent, there was a detent gate for forward and reverse too.
It took a few minutes before I quit shaking, but ever thereafter I checked by turning the chuck to see if it was in neutral before changing chucks or tightening one, and also was very careful of that lever.
I suppose someone would object to showing high school kids videos of shop accidents, but that or near misses like mine is what gets and holds one's attention around machinery.
