Re: This is how not to operate a lathe!
wrong wrong wrong wrong wrong.
Oh man do I ever cringe, when I see things like that. Yes, obviously he was tightening (screwing around with) the chuck wrong.
At no time EVER should anyone else be even thinking of starting it, let alone 'doing it'. ARrggg
We had a kid in our shop class, who went around sabotaging other's lathes on purpose. He'd put the chuck key in, at the back. So that when whomever came back to their work, and turned the machine on, it would fly/catapult across the shop. Hitting nobody if they were lucky. He'd also disconnect the feed-range selector, so that it would bounce back and forth and absolutely destroy the micarta idlers inside.
Very unpopular individual, whom got expelled. Among other things.
Shops just AIN'T no place for dorking around.