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A jackhammer (pneumatic drill, breaker, demolition hammer or road hammer in Commonwealth English) is a pneumatic or electro-mechanical tool that combines a hammer directly with a chisel. It was invented by William McReavy, who then sold the patent to Charles Brady King. Hand-held jackhammers are generally powered by compressed air, but some are also powered by electric motors. Larger jackhammers, such as rig-mounted hammers used on construction machinery, are usually hydraulically powered. These tools are typically used to break up rock, pavement, and concrete.

A jackhammer operates by driving an internal hammer up and down. The hammer is first driven down to strike the chisel and then back up to return the hammer to the original position to repeat the cycle. The effectiveness of the jackhammer is dependent on how much force is applied to the tool. It is generally used like a hammer to break the hard surface or rock in construction works and it is not considered under earth-moving equipment, along with its accessories (i.e., pusher leg, lubricator).

History

The first steam-powered drill was patented by Samuel Miller in 1806. The drill used steam only for raising the drill. Pneumatic drills were developed in response to the needs of mining, quarrying, excavating, and tunneling. A pneumatic drill was proposed by C. Brunton in 1844. In 1846, a percussion drill that could be worked by steam, or atmospheric pressure obtained from a vacuum, was patented in Britain by Thomas Clarke, Mark Freeman, and John Varley. The first American "percussion drill" was made in 1848, and patented in 1849 by Jonathan J.

Terminology

The word "jackhammer" is used in North American English and Australia, while "pneumatic drill" is used colloquially elsewhere in the English-speaking world, although strictly speaking a "pneumatic drill" refers to a pneumatically driven jackhammer.

In Britain, electromechanical versions are colloquially known by the name of "Kangos". The term comes from the former British brand name now owned by Milwaukee Tools.

Use

A full-sized portable jackhammer is impractical for use against walls and steep slopes, except by a very strong person, as the user would have to both support the weight of the tool and push the tool back against the work after each blow. A technique developed by experienced workers is a two-man team to overcome this obstacle of gravity: one operates the hammer and the second assists by holding the hammer either on his shoulders or cradled in his arms. Both use their combined weight to push the bit into the workface.

Types

Pneumatic

A pneumatic jackhammer, also known as a pneumatic drill or pneumatic hammer, is a jackhammer that uses compressed air as the power source. The air supply usually comes from a portable air compressor driven by a diesel engine. Reciprocating compressors were formerly used. The unit comprised a reciprocating compressor driven, through a centrifugal clutch, by a diesel engine. The engine's governor provided only two speeds:

idling, when the clutch was disengaged

maximum, when the clutch was engaged and the compressor was running

Bits

Bit types include:

Spade – provides flat finish for concrete or edging in asphalt or dirt.

• Flat tip – allows direction control or finer edge finish
• Point – general breaking
• Stake driver – drives concrete form stakes
• Scabbler – finishes surface smooth or for cleaning prior to bonding

Flex chisel – flexible metal blade (attached to shank with bolts) for tile removal and scraping

Bushing tool – multiple carbide points for cleaning up seams and knocking down rough spots in concrete

Health effects

The sound of the hammer blows, combined with the explosive air exhaust, makes pneumatic jackhammers dangerously loud, emitting more than 120 dB SPL near the operator’s ears. Sound-blocking earmuffs and earplugs must be worn by the operator to prevent a form of hearing loss, of which tinnitus is the main symptom. Although some pneumatic jackhammers now have a silencer around the barrel of the tool, loud air exhaust, hammer blows themselves, and compressor engine sounds remain unmuffled.