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5. Rotary Drill Rigs and Rock Drills. Rotary drill rigs create holes through rock or soil, allowing placement of charges for blasting open mines. A rotary drill rig is one of two main types of drills used for mining. The other type is a percussion or hammer drill. For a rotary drill rig, the drill bit turns under pressure to cut into the rock.Rail-track laying and maintenance equipment operators. Lay, repair, and maintain track for standard or narrow-gauge railroad equipment used in regular railroad service or in plant yards, quarries, sand and gravel pits, and mines. Includes ballast cleaning machine operators and railroad bed tamping machine operators. 2021 employment: 17,000
