A down-the-hole drill, usually called DTH by most professionals, is basically a screwed on the bottom of a . The fast hammer action breaks hard rock into small cuttings and dust that are evacuated by a fluid (air, water or ). The DTH hammer is one of the fastest ways to drill hard rock. The system is thought to have been invented independently by Stenuic. [pdf]
John Henry is an American . An African American , he is said to have worked as a "steel-driving man"—a man tasked with hammering a steel drill into a rock to make holes for explosives to blast the rock in constructing a railroad tunnel. The story of John Henry is told in a classic blues folk song about his duel agai. [pdf]
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