key (verb). To initiate an action by depressing a key or a button.
keyhole saw. A small handsaw with a stiff, tapered blade. The blade of a keyhole saw can start its cut through a small hole drilled in the material. A key-hole saw is a form of compass saw.
keyway. A lengthwise groove cut in the outside of a shaft. A similar keyway cut into the side of the hole in the hub that fits on the shaft is aligned with the keyway on the shaft, and a rectangular piece of metal called a key locks the keyways together, preventing the hub turning on the shaft.
K-factor (sheet metal layout). A factor used in sheet metal work to determine the setback for other than a
90° bend. K-factors are found in charts in most sheet metal working handbooks.
Setback = K . (bend radius + metal thickness).
For bends of less than 90°, the value of K is less than 1; for bends greater than 90°, the value of K is greater than 1.
kHz. The abbreviation for kilohertz (1,000 cycles per second).
kickback (reciprocating engine operation). A condition of engine operation in which the engine tries to run backward when it is being started. Kickback is caused by the ignition spark occurring while the piston is moving slowly upward on the compression stroke. Since the piston is moving slowly, the pressure from the expanding gases is applied to the piston before it passes over top center of the compression stroke. Kickback is prevented by timing the ignition so the starting spark occurs late.
kick-in pressure (hydraulic system operation). The pressure at which an unloading valve causes a hydraulic pump to direct its fluid into the system manifold.
kick-out pressure (hydraulic system operation). The pressure at which an unloading valve shuts off the flow of fluid into the system pressure manifold and directs it back to the reservoir under a much reduced pressure.
kilo (k). The metric prefix that means 1,000. A kilogram is one thousand grams, a kilometer is one thousand meters, and a kilohertz is one thousand cycles per second.
kilogram. One of the commonly used units in the metric system for measuring mass. One kilogram is the mass of one thousand cubic centimeters of pure water. In the International Bureau of Standards in Paris, France, there is a cylinder of platinum having a mass of exactly one kilogram. It is known as the standard kilogram.
kilomega (kM). A term that has, in the past, been used to represent the quantity 1,000,000,000 or 1 x 109. The prefix giga is now used in place of kilomega.
kindling temperature. The temperature to which a material must be heated for it to combine with oxygen from the air and burn. The kindling temperature of a material is also called its ignition temperature, or its kindling point.
kinematic viscosity. The ratio of the absolute viscosity of a fluid to its density. Kinematic viscosity is measured in centistokes.
kinetic energy. Energy in an object caused by its motion. Kinetic energy is equal to one half the mass of the body times the square of its speed.
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