Some types of metal such as thin sheets of aluminum and magnesium alloys are normally bent cold, but other metals, especially thick sections of steel, are heated red-hot before they are bent.
cold-cathode vacuum tube. A vacuum tube, or electron tube, whose cathode is made of a material that emits (gives off) electrons at normal room temperature. Cold-cathode vacuum tubes do not have filaments, or heaters.
cold chisel. A metal-cutting tool made by grinding a sharp edge onto a flattened portion of a hardened steel rod. A cold chisel is used to cut metal when the metal is cold.
cold circuit (electrical circuit). An electrical circuit that is not energized— not connected to a source of electrical power.
cold-cranking amps (battery rating). A measure of the capacity of a battery when it is supplying a high rate of current, such as it would if it were being used to crank a cold engine.
The cold-cranking amps discharge rate is similar to the five-minute discharge rate that specifies the number of ampere-hours of capacity the battery has when it is discharged at a rate that will drop its cell voltage to a specified low value in five minutes.
The ampere hour capacity of a battery at its five-minute discharge rate is much lower than its capacity at the other discharge rates. The actual capacity at this rate is given in the specifications the manufacturer issues for each battery.
cold-cranking simulation (lubricating oil specification). A method used for specifying the characteristics of a lubricating oil at low temperature. Oils that have been rated by this test are identified by the letter W (standing for Winter) in their designation. For example, SAE 15W50.
cold cylinder test (air-cooled engine maintenance test). A maintenance test used to identify the cylinder in an air-cooled engine which is not firing.
When a cylinder is not firing, the temperature of the exhaust stack near the head is colder than the temperature measured at the same place on a cylinder that is firing normally.
Hand-held temperature gages, called magic wands, can be used to find the cold cylinder, but on most small engines the cold cylinder can be located by feel.
cold dimpling (sheet metal work). A method of preparing a hole in sheet metal to receive flush rivets. A male dimpling die forces the metal around the rivet hole into a female die to form a depression into which the rivet head fits.
A countersunk-head rivet fits into a dimpled hole in such a way that the top of the head is flush with the surface of the metal.
cold drawing. A method of reducing the diameter of a wire or tube by drawing it through a series of progressively smaller dies without the wire or tube being heated.
cold flow (condition of fluid hoses). A deep, permanent deformation of a flexible hose, caused by pressure applied by the hose clamps.
cold front (meteorology). Any nonoccluded front which moves in such a way that cold air replaces warmer air.
cold junction (thermocouple junction). The reference junction of a thermocouple. A thermocouple is a generator of electrical current made of two dissimilar metal wires connected into a loop. The ends where the two wires are joined are called junctions.
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