A chisel drill, also known as a hammer drill or impact drill, is a handheld power tool similar to the larger scale jackhammer, designed to break up rock and other hard materials. Man-made materials such as masonry and precast stone often require the addition of holes for wiring and plumbing lines in the construction trade, and these holes are made with a chisel drill. They can operate in a rotary or hammering manner to drill or chip at surfaces such as concrete. Often, a chisel drill is referred to in the trade as a masonry drill because it is usually used to punch holes through concrete and man-made types of rock material such as stucco or cinder blocks.
The purpose a chisel drill in construction involves the drilling of holes with a diameter of less than 2 inches (51 millimeters). Long holes are bored by the attachment of drill rods to the chisel drill and they are capable of drilling to a depth of 16.5 feet (about 5 meters). Chisel drill bits themselves have a tapered edge of 7° for soft rock drilling, and up to 11-12° for harder formations, and are usually made from tungsten carbide.
Buying a chisel drill or hammer drill has become easier in recent years, as the technology is now incorporated into some standard rotary drill designs that can function as two tools in one with the flip of a switch. Using a chisel drill in the past meant running an extension cord to the nearest electrical outlet. Lithium ion and nickel cadmium batteries generate up to 28 volts on larger models, making cordless drills much more convenient to use on a job site where there might not be easy access to electrical power. Smaller 14.4-volt drills are also available and are more lightweight and portable, though the batteries last only about half as long.
Using a chisel drill on steel is also a common application by electrical contractors to anchor electrical power boxes and run conduit for wiring. Generating the thousands of beats per minute that one of these drills uses to penetrate such tough materials is done with a rotating cam design inside the drill or a pneumatic action powered by electricity. Some drill models also have attachments to collect dust, as a large volume of rock dust can be produced. In hospitals and sensitive computer environments, this can be a hazard.
