EE WAS DISMANTLING THE CONE BOWL WORK LINER. LINER IS CEMENTED IN PLACE & MUST BE JARRED LOOSE TO REMOVE. THE LINE EDGE CANNOT BE REACHED WITH SLEDGE, THEREFORE THE SLEDGE IS IMPACTED ON THE E DGE. EE SWUNG THE 16LB SLEDGE ABOUT 5 TIMES BEFORE HE FELT SOMETHING GIVE IN LOWER BACK & HE QUIT WORKING. HE THEN USED HAMMERDRILL Y