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Pneumatic operation
A pneumatic drill or jackhammer is a portable percussive-drill, operated by compressed air and used to drill rock, break up pavement, etc. It works in the manner of a hammer and chisel, by jabbing with its bit, not by rotating it. (A drill, driven by compressed air, which rotates its cutting bit is called an air-drill or, more familiarly, a windy-drill.) The word jackhammer is used in North American English and in Australia, and pneumatic drill is used elsewhere in the English speaking world. The portable pneumatic jackhammer is impractical for use on walls and steep slopes as it relies on the inertia of the mass of its body to impel the bit into the work and manipulating that mass when it is not supported by the work is highly difficult. Besides, gravity is required to bring the mass back into contact with the work after each blow. Though it is unhealthy practice, the operator may lean on the tool to assist but he is not really capable of overcoming the forces involved when he/she is not assisted by gravity.
Its pneumatic hose connections are designed so that any hose end will connect with any hose end without the workman having to keep track of male and female hose-ends: see Gender of connectors and fasteners.
Hydraulic operation
A hydraulic jackhammer (on a much larger scale than the portable ones) may be fitted to mechanical excavators and is widely used on roadwork, quarrying and general demolition or constructional groundwork. In mining, it is possible to use this against a vertical wall as the machine can be jacked off the opposite wall of the gallery or some comparable device. For reasons of safety, pneumatic tools are likely to be used underground on a coal mine.
Hydraulic breakers will usually use a hydraulic motor to drive a sealed pneumatic hammer system, as a hydraulic hammer would not only develop a poor striking speed but transfer unacceptable shock loads to the pump system.
Electro-mechanical operation
While the term "jackhammer" is occasionally used to mean "pneumatic drill", the electro-mechanical tool that performs the same function is normally the one called a "jackhammer" in Britain. This tool is useful where the work is light and not accessible from a compressor.
Health
The sound of the repeated hammer-blows combined with the explosive exhaust of the air, makes pneumatic jackhammers dangerously noisy, emitting 100 decibels at two meters. Sound-blocking earmuffs must be worn by the operator to prevent a form of hearing damage of which tinnitus is the main symptom. As a result, most pneumatic jackhammers now have a silencer around the barrel of the tool: it is the black part in the image below.
Prolonged exposure to the very pronounced vibration set up by the tool can lead to blood-circulation failures in the fingers, a condition known as white finger.
Images
"Jackhammer"