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How Does a Pneumatic Drill Work?

Ezmeralda Lee

What is a pneumatic drill? The word “pneumatic” when used in the world of tools is used to describe machinery operated by gas or air that is under pressure. A pneumatic drill, or air drill, is a large mechanical drill powered by compressed air.


Though several different sizes of drills can be powered pneumatically, a true pneumatic drill will also be referred to as a jackhammer, and is typically used in roadwork applications, when rock, pavement and sidewalk must be broke down.

Pneumatic Power: Fueling the Tank

The air that powers a pneumatic jackhammer drill is delivered to the drill from a compressor. The compressor resembles an electric generator on wheels, and can be run by electric power, but more often, is run by a diesel engine. The compressor machine delivers the air at high pressure through a thick cord-like tube that connects to the pneumatic drill.

Pneumatic Power At Work

The compressed air supply is not the only energy that powers the pneumatic drill. The drill relies hugely on gravity and Newton’s third law of motion: “what goes up must come down."

Inside the pneumatic drill is a series of air tubes that connect to the pile driver, and then to the drill bit at the bottom. The compressed air, delivered from the diesel-powered compressor, enters the drill and moves through the air tube circuit system. The movement of the air pushes the pile driver down onto the drill bit, causing the drill bit to pound into the surface of the road, sidewalk or pavement being drilled. The downward movement of the drill, in combination with the vibration of the drill pounding into the surface, causes a valve inside the air tubing to invert. This valve’s inversion causes the air to circulate in the opposite direction; the new flow of air causes the drill to bounce back away from the earth. The valve then flips again, and the air flow, combined with the power of gravity, forces and pulls the drill bit back to the surface.

All of this happens very rapidly. The drill bit smashes into the surface at an average of 25 times per second, 1500 times a minute. You can easily see how this would be more effective than a man (or woman) swinging a sledge hammer only 5 or 10 times in a minute.

Safety Precautions Used When Powering a Pneumatic Drill

Road crew managers usually only allow persons of larger stature to operate pneumatic jack hammer drills. Some companies require a training session and a certification program before they will allow employees to use a pneumatic drill.

Pneumatic drill operators are exposed to both the loud sounds of the engine powering the drill and the loud sounds of the hammer pounding into the surface; because of this, they are required to wear earmuffs to prevent hearing loss or damage.

As another precaution, operators are typically not permitted to run the pneumatic drill for long periods of time. The vibrations caused by the drill and the tight grip required to keep control, cause the operators' circulation to become poor, and can also negatively affect the tendons in the operators hands, arms and wrists, leading to carpal tunnel syndrome.