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A Drifter is either a hydraulic or pneumatic powered rock or ground drill placed on top of a feed. The feed is like a rail that the drill travels on, aka. drifts. This kind of drilling procedure is also called drifting. The feed is usually attached with a flexible boom (like an arm) to a stationery or mobile unit that contains the powerpack (engine and hyd. pump or compressor). Drifters are used in mining, construction, exploration and natural science.
A hydraulic rock drill or drifter is usually a machine, that consists of a percussive system and a rotative system. The percussive system strikes the drill steel, for example 2000-5000 strikes per minute as the rotation can be, for example, 100-400 rounds per minute. Combined together, these functions enable drilling holes into rock. The excess material (cuttings) is then pushed up from the bottom of the hole by means of pressurized air or water.
Hydraulic rock drills are also called hydraulic top hammers, which explains the position of the actual drilling device concerning the drill rod. Opposite to a top hammer drill or drifter is the down-the-hole hammers, which are usually pneumatic.
Early rock drills
In 1849, J. J. Couch, an American inventor from Philadelphia, received the first patent for a rock drill. The first rock drill featured a drill rod which passed through a hollow piston and was thrown against the rock.