Hammer Drill

(redirected from hammer drills)
Also found in: Dictionary.
Related to hammer drills: electric drill

hammer drill

[′ham·ər ‚dril]
(mechanical engineering)
Any of three types of fast-cutting, compressed-air rock drills (drifter, sinker, and stoper) in which a hammer strikes rapid blows on a loosely held piston, and the bit remains against the rock in the bottom of the hole, rebounding slightly at each blow, but does not reciprocate.

Hammer Drill

 

a percussion boring machine for drilling blast holes (less frequently well holes). The hammer drill is usually a pneumatic machine; power drills with gasoline engines are seldom used. In the first hammer drills (mid-19th century) the cutter performed its operation with a piston (so-called piston drills). These were later replaced by drills of the hammer type, in which the piston strikes the drill shaft, to which a rock-crushing drill bit is fastened. The bit turns 10°-15° on each return stroke of the piston. (The rotation is transmitted from the piston to the drill by a swivel gear.) Hammer drills with independent rotation, in which the drill is turned by a special air compressor, have been developed. Piston motion is controlled by an air-distribution device that supplies consecutive charges of air to the front and rear cylinder cavities. The crushed rock is removed from the blast hole by water or compressed air.

Hammer drills are classified as follows: hand-held jack-hammers (light, medium, and heavy-duty), weighing 10-30 kg, which are held in the drill operators’ hands or are mounted on a pneumatic support during the drilling operation; core hammer drills, weighing 50-70 kg, which are mounted on mobile drilling rigs or on columns with an automatic power supply; and telescoping borehammers, weighing 30-40 kg, for drilling upward-directed blast holes.

Hammer drills are rated according to the energy of a single impacts A= mv2/2 (m is the piston mass, and v is the velocity before impact), the number of impacts per minute n, the air flow rate, and the mass of the drill. The most efficient hammer drills are those with higher impact energy and an n rating of up to 2,000 impacts per minute. High-frequency hammer drills with n ratings above 2,500 impacts per minute are used only when mounted on mobile drilling rigs or manipulators, owing to their excessive noise level (up to 120 decibels) and high vibrations. Vibration-damping handles and mufflers have been developed to lessen the harmful effects of the vibration and noise on the drill operators.

REFERENCES

Tekhnika bureniia pri razrabotke mestorozhdenii poleznykh iskopaemykh. Moscow, 1966.
Pnevmaticheskie ruchnye mashiny: Spravochnik. Leningrad, 1968.

B. N. KUTUZOV

hammer drill

A percussive-type pneumatically powered rock drill.
References in periodicals archive ?
Many hammer drills can be used as a regular drill by switching off the hammering action.
Rotary hammers provide a lot more impact energy than hammer drills.
Some heavy-duty drills or hammer drills feature a pivoting handle located at the front of the drill so the user can apply extra force.
With the proper accessories, hammer drills can sand, polish and operate like a mini-drill press.
Lester Gothard, a subcontractor with Goehrs Builders in Coldsprings, Texas, relies on a DeWalt 18-volt hammer drill for boring 2-inch holes into 3/8-inch concrete.
Twenty years on, the company invented the hammer drill, and, in 1966, followed with the invention of its patented S-automatic safety clutch which protects users from excessive back-twist torque.
If you're going to buy a corded drill, get a hammer drill," said Joe Jensen, set builder for The Family Handyman and home improvement contractor.
Corded hammer drills cost $65 to $400, or you can buy a cordless model starting at $230.
Most hammer drills have a switch or collar so you can change over from hammer drilling to regular drilling.
Hammer drills not only spin the bit but also hammer it forward thousands of times per minute.
Most hammer drills come with a couple of accessories to help you operate them properly.