This idle period may have contributed to a breakdown on 27 September 1984 : after drilling to 12,066 m ( 39,587 ft ) , a 5,000 m ( 16,000 ft ) section of the drill string twisted off and was left in the hole .
On September 27 , 1984 , the machine broke at a depth of 12,066 m or 39,587 ft ; its drill string twisted off and was left in the hole .