drift sight (aircraft navigation instrument). A navigational instrument used in an aircraft when it is being navigated by dead reckoning. The drift sight measures the angle between the direction the aircraft is pointed and the direction it is moving over the ground.
drill (rotary cutting tool). A pointed rotary cutting tool rotated under pressure in a drill press or with a hand-held drill motor to cut a hole in a piece of solid material. A drill is correctly called a twist drill.
drill bushing. A hardened steel bushing installed in an assembly fixture. A piece of metal to be assembled is clamped in the fixture, and a twist drill is guided by the bushing to drill a hole at the correct location. The hardened metal prevents the bushing being worn by the drill.
drill chuck (machine tool component). A three-jaw clamp attached to the spindle of a drill press or the shaft of a drill motor to hold a twist drill centered. The jaws of the chuck may be tightened on the drill with a chuck key or Allen wrench, and some chucks are designed to be tightened by hand.
drill motor. An electric or pneumatic motor that drives a chuck which holds a twist drill. The best drill motors produce high torque, and their speed can be controlled.
drill press. A power tool used for drilling holes in metal or wood.
The drill press consists of a motor-driven spindle on which is mounted a drill chuck that holds a twist drill.
The material to be drilled is placed on a steel table under the spindle, and the spindle is forced down, causing the drill to cut into the material.
drill rod (metallurgy). A rod of steel having a carbon content of at least 0.85%.
drip loop (electrical wiring). A half loop of wire at the cable entrance of an exposed junction box. The final section of the cable runs upward, preventing water entering the box.
drip pan. A shallow metal pan placed under the engine of an aircraft when it is in the hangar to catch any oil that might drip from it.
drip-stick fuel gage (fuel quantity indicator). A type of visual fuel-quantity indicator used on large aircraft to measure the amount of fuel in a tank. The drip stick, which is normally locked in the tank in its up position, is unlocked and slowly pulled down from the bottom of the tank. The bottom of the drip stick is watched until the first drips of fuel come from it. At this point, the top of the drip stick is level with the top of the fuel in the tank.
Marks on the outside of the drip stick at the point it leaves the tank show the amount of fuel in the tank.