Hammer Drill


Also found in: Dictionary, Wikipedia.

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 ?
The line now includes a 20V MAX* Hammer Drill and 20V MAX* Radio with Bluetooth[sup.
With an improved ergonomic design which assists driving, and a drop-in keyless hex driver, it is perfect for quick one-handed bit changes and is also available in a twin pack with the hammer drill.
8v lithium ion drill is perfect for working in tight spaces where a larger hammer drill may not fit the bill.
However, the worst day was when plaster began falling from the ceiling and I realised that a hammer drill was coming through the roof.
This is a heavy-duty cordless rotary hammer drill with chisel action which sounds like it will make short work of any drilling tasks around the house.
B&Q complained to the Advertising Standards Authority after a Lidl ad for an own-label hammer drill boasted its 49.
Last weekend, a hammer drill, a transformer and drill bits were taken from a Ford Courier parked in Deansway, and a jigsaw, a battery drill, a hammer drill and a circular saw, all made by Pro Performance, went from a Ford Transit in Harmar Close.
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 have to drill a number of holes in hard concrete, you can rent a hammer drill for about $10 per day (rental costs may vary from store to store).
Limited Tenders are invited for 1)Rotary Hammer Drill Machine Suitable For Drilling 6-32 Mm Dia Drill In Concrete, Power Input: 900 W +/- 50 W, No Load Speed: 0-760 +/- 50 Rpm, Single Impact Energy:0-5J, Weight: Upto 3 Kg.
Even in granite-like conditions the new Cat MD5150C Top Hammer Drill is out-performing down-the-hole rigs, according to the company, with its higher productivity and much lower fuel consumption--while achieving comparable hole straightness.