drill

drill tool used to create a hole, usually in some hard substance, by its rotary or hammering action. Many different tools make up the drill family. The awl is a pointed instrument used for piercing small holes. In its early form it was a thorn or a tool of bone or chipped flint; many prehistoric awls of flint have been found. The gimlet, which consists of a cross handle holding a metal shaft with a screw point, is used for boring small holes. Its principle and that of a similar tool, the auger, were known and used in ancient times, but the tools were much improved in the Middle Ages. The auger has a cross handle containing a shaft that usually ends with a central screw-shaped point; the point acts to pull two knife edges about it into the material to do the actual cutting. Spiral channels extend part way up the shaft to allow chips to be removed from the hole. The term auger is also applied to various augerlike tools. More elaborate types of drills are composed of two main parts: a replaceable device that does the actual cutting, called a bit, and a second device that drives it. Both devices may be referred to as drills. Two common types of rotary bits are the auger and the twist bit. Hand-powered rotary driving devices include the hand drill, which has a crank that transmits turning power to the bit through a gear and pinion, and the bit brace, which is a bow-shaped device that is rotated to turn a bit. Motor-powered rotary driving devices include the drill press and the portable electric drill, both used at home or in industry for cutting holes in such materials as metal, wood, and plastic. The core drill cuts an annular hole through minerals. For a small hole the drill bit may contain diamonds, which bore a hole by their abrasive action when they are rotated. A rotary oil well drill uses a bit containing either rolling cutters with hard teeth or a fixed, chisel cutting edge. The percussive types of drill force a bit to move forward by a hammering action that chips away material, instead of cutting or abrading it. For example, an air percussion drill chips through rock with a cross-shaped bit driven by a piston; the similar churn drill is lifted and dropped by cable. One special kind of drill, the fusion drill, creates a hole by melting or flaking minerals with an oxyacetylene torch. An agricultural implement for planting certain seeds or for placing fertilizer in the soil is called a drill. Small drills for gardens are pushed by hand; large drills for field work are drawn by horses or tractors. The agricultural drill is named for its special uses, e.g., the grass drill and the grain drill, or for its construction, as the disk drill and the hoe drill. The fertilizer drill is commonly combined with the seed drill.

drill¹ / dril/ • n. 1. a hand tool, power tool, or machine with a rotating cutting tip or reciprocating hammer or chisel, used for making holes. ∎  such a tool used by a dentist for cutting away part of a tooth before filling it. 2. instruction or training in military exercises. ∎  intensive instruction or training in something, typically by means of repeated exercises. ∎  a rehearsal of the procedure to be followed in an emergency. ∎  (the drill) inf. the correct or recognized procedure or way of doing something: he didn't know the drill. 3. a predatory mollusk (family Muricidae, class Gastropoda) that bores into the shells of other mollusks in order to feed on the soft tissue. • v. [tr.] 1. produce (a hole) in something by or as if by boring with a drill. ∎  make a hole in (something) by boring with a drill. ∎  [intr.] make a hole in or through something by using a drill: fig. his eyes drilled into her. ∎  [intr.] sink a borehole in order to obtain a certain substance, typically oil or water: they are licensed to drill for oil in the area | [as n.] (drilling) drilling should begin next year. ∎  (of a dentist) cut away part of (a tooth) before filling it. ∎  [tr.] inf. (of a sports player) hit, throw, or kick (a ball or puck) hard and in a straight line. 2. subject (someone) to military training exercises. ∎  [intr.] (of a person) take part in such exercises. ∎  instruct (someone) in something by the means of repeated exercises or practice. ∎  (drill something into) cause (someone) to learn something by repeating it regularly. DERIVATIVES: drill·er n.

drill