REMOVING/REPLACING DAMAGED MANTLE FROM TELSMITH SILVER BULLET CONE CRUSHER. TAPERED HEAD & SHAFT REMOVED FROM CRUSHER, POSITIONED ON BLOCKING (ATOP OF SAW HORSES). DISTANCE FROM GROUND 3-4 FT. EE TOLD TO CUT BURNING RING & WAIT FOR HELP. EE W/O HELP, LOOSENED NONSTABLIZED SHAFT NUT W/SLEDGE HAMMER. DIDN'T REALIZE HOW LOOSE NUT WAS, SHAFT NUT & WRENCH FELL OFF SHAFT HEAD (100-150 LB