DRILL

(Mandrillus leucophaeus), large, short-tailed monkey, family Cercopithecidae, formerly found from Nigeria to Cameroon. As a result of hunting and deforestation, the drill is an endangered species restricted to remote forest regions of Cameroon. The drill, like the related mandrill (q.v.), is sometimes placed in the baboon genus, Papio. Like the mandrill, the drill is a stout-bodied, quadrupedal monkey with vividly coloured buttocks. It is, however, smaller (the male is about 82 centimetres [32 inches] long) and has a black face. The lower lip is crimson; the hairs around the face and a tuft behind the ears are yellowish white; and the rest of the fur is olive-brown. The drill is also like the mandrill in being diurnal, omnivorous, mainly terrestrial, and, apparently, gregarious. A powerful animal, it can fight ferociously if molested. preparation of soldiers for performance of their duties in peace and war through the practice and rehearsal of prescribed movements. In a practical sense, drill consolidates soldiers into battle formations and familiarizes them with their weapons. Psychologically, it develops a sense of teamwork, discipline, and self-control; it promotes automatic performance of duties under disturbing circumstances and instinctive response to the control and stimulus of leaders. Modern drill is essentially of two types: close-order and extended-order, or combat drill. Close-order drill comprises the formal movements and formations used in marching, parades, and ceremonies. Combat drill trains a small unit in the looser, extended formations and movements of battle. Rudimentary drill appeared in ancient Egypt with the dawn of formal warfare because of the need to assemble and move large numbers of men for battle. Drill in the modern sense was introduced by the Greeks, who periodically practiced the maneuvers of the phalanx; the Spartans carried disciplined drill to an extreme unequalled by their contemporaries. Philip II of Macedonia and Alexander III the Great further improved the phalanx and its drill. The careful training of the legions contributed largely to Roman domination of the Mediterranean world for almost a thousand years. After Rome's decline, military drill almost disappeared as warfare degenerated into undisciplined melees and individual dueling. Two notable exceptions were the well-trained professional armies of Byzantium and the disciplined cavalry formations of Genghis Khan and his successors. Gustavus II Adolphus of Sweden accelerated a gradual revival of skill in European warfare early in the 17th century. His introduction of simplified drill techniques for the use of improved weapons was copied by all Europe. By the end of the 17th century, France led in the development of modern standing armies, largely because of a drill system devised by Louis XIV's inspector general of infantry, Jean Martinet, whose name became a synonym for drillmaster. To make effective use of inaccurate muskets, concentrated volleys had to be delivered at short range. Troops advanced in rigidly maintained battle lines, all firing simultaneously on command. Through ceaseless drill, the Prussian Army of Frederick II the Great achieved a mechanical perfection in these tactics. At Valley Forge during the American Revolution, Baron von Steuben, a German officer who helped train American troops, adapted Prussian techniques into a less rigid drill system fitted to the American character and to conditions of warfare in the New World. Exact parade ground maneuvers on the battlefield disappeared in the 19th century because of improvements in the range and accuracy of weapons. This trend began during the American Civil War, when soldiers had to be trained to spread out, take cover, and dig entrenchments. It was hastened later by the introduction of the machine gun and quick-firing artillery. Close-order drill, however, was retained not only because it had value for ceremonies and for moving large bodies of men on foot but also because it provided a psychological foundation of teamwork and discipline without which combat drill is impossible. cylindrical end-cutting tool used to originate or enlarge circular holes in solid material. Usually, drills are rotated by a drilling machine and fed into stationary work, but on other types of machines a stationary drill may be fed into rotating work or drill and work may rotate in opposite directions. To form the two cutting edges and to permit the admission of a coolant and the ejection of chips, two longitudinal or helical grooves or flutes are provided. The point, or tip, of a drill is usually conical in shape, and it has cutting edges where the flutes end. The angle formed by the tapering sides of the point determines how large a chip is taken off with each rotation of the drill. The degree of twist of the helical flutes also affects the drill's cutting and chip-removal properties. For general-purpose twist drills the helix angle is about 32. The angle formed by the two sides of the tapering point is 118 for standard drills, while for drilling tough metals, a flatter point with a 135 angle is recommended. The peripheral portion of the drill body not cut away by the flutes is called the land, and to reduce friction and prevent the land from rubbing against the sides of the hole, most of the land is cut away, leaving a narrow ridge called the margin that follows the edge of the side of the flute that forms the cutting edge. The fluted part, or body, of a drill is either hardened high-carbon steel or high-speed steel; other drills have inserts of cemented carbide to form cutting edges or are made from sintered-carbide rods. The shanks of twist drills are either straight or tapered and when not integral with the body are made from low-carbon steel and welded to the body. Straight-shank drills must be gripped in a chuck; tapered shanks fit with a sticking taper in matching holes in the machine and are driven partly by the taper and partly by a tang that fits in a slot in the machine. For enlarging cored, punched, or drilled holes, core drills are particularly suited. These have three or four flutes, and because the cutting edges do not extend to the centre of the drill, they cannot originate holes in solid materials. Cutting is accomplished by a chamfered edge at the end of each flute. See also auger.