A percussion drill is a drill that works through percussion action, creating a hole in the ground with repeated impacts using a weighted head. This drill design is thousands of years old and evidence of percussion drilling can be seen in a number of ancient cultures, perhaps most notably in China, where percussion drills were used to create brine wells for salt refining. There are several variations on the basic design in use today.
The original percussion drill consists of a long, weighted pole rigged over a hole with block and tackle or a pulley system. The pole is repeatedly lifted up by users and then allowed to fall, the weight driving it deeper into the ground with each fall. Percussion drilling takes longer than power drilling, but is usable in low-technology areas where access to other types of drills is not feasible. Several charities working in developing nations have introduced percussion drilling as an alternative to hand dug wells, as this method is faster and requires less labor.
Other percussion drills use an air driven piston. Puffs of air push the piston, driving the end of the drill to deepen the hole. Percussive drilling of this type can be used in a variety of settings, and these drills are capable of penetrating materials ranging from loose soil to rock. This design requires somewhat more technology than the original and is highly effective.
No matter what kind of drill is being used, a percussion drill can be noisy. Ear protection should be worn by drill operators to reduce the risk of hearing loss. Eye and facial protection may also be advised, depending on what is being drilled, as the drilling process can stir up particulate materials that may cause irritation if they land in the eyes or are inhaled. Protection can be as simple as wrapping the mouth and nose in a cloth in regions where more advanced facial protection is not available.
As a percussion drill is operated, there is a risk that the walls of the hole will start to collapse. In cases where this is a concern, a long tube can be advanced with the percussion drill. Known as the casing, this tube will keep the hole open, preventing a collapse, and it will also help guide the drill as it is used. Once a satisfactory depth is reached, the casing can be fixed in place to make the hole as permanent as possible.