THREE MINORS WERE ASSIGNED TO RIG UP A HAUL TRUCK AXLE TO LOWER DOWN THE 14' DIAM. SHAFT AFTER RIGGING HOIST THEY FAILED TO WAIT FOR SUPERVIOSR AS INSTRUCTED AND FAILED TO FOLLOW HAVING PROCES URE BY PLACING THE AXLE OVER THE OPEN SHAFT WITHA TELESCAPING FORK HIT. THE WEIGHT OF THE AXLE SLID OFF THE FORKS FAILLING DOWN THE SHAFT RESULTING IN EXTONSIVE SHAFT DAMAGE.