My dad was a high school shop teacher for 30 years. Only had 2 kids get hurt during that time. One was with this situation, student had something like a 3/8" steel rod chucked up with 3' sticking out of the head stock. He had "V" cradles made up from the welding class; base was a cross of channel, vertical steel pipe with a nut welded at the top, used a bolt to lock to a vertically adjustable piece of pipe fit inside the one with the base welded to it. There was a "V" welded at the top, couple of pieces of 1" CRS rounds. Idea was to set the support under the stock and adjust the height, then start the lathe at slow speed (he had Clausing 5914's in the shop, variable speed) and take it up to speed. The student didn't use the outboard support and had the rod do a 90 bend and whopped him in the shoulder, lucky it didn't hit him in the head. He had a nice bruise. My dad said the lathe was vibrating across the floor until he hit the master power switch.
Bruce