Chuck up a piece of 1″ pipe that extends into headstock and has 8″ sticking out. Apply a 24″ pipe wrench near the chuck face pull with left hand and apply hammer smartly to the pipe wrench with the right hand. This gives something to hold onto and keeps from falling on the ways. A large nut welded to the end of a rod chucked similarly. 3/4 Impact applied to nut can work without getting the gear train involved.