Injured was polishing a 22"" long, 2"" in diameter pin on the shop lathe. EE was using a 4 foot long piece of emery cloth. When the emery cloth was worn, EE choked up on one end of the emery cloth to have better grid on the emery cloth. As EE was working the emery cloth back and forth, EE got EE's thumb too close to the bar and the rotating bar pulled EE in and broke EE's left arm.