J bolt: A J-shaped bolt, threaded on the long leg of the J.
J box: NULL
J factor: A dimensionless equation used for the calculation of free convection heat transmission through fluid films.
Jacobs taper: A machine tool used for mounting drill chucks in drilling machines.
Jaeger-Steinwehr method: A refinement of the Griffiths method for determining the mechanical equivalent of heat, in which a large mass of water, efficiently stirred, is used, the temperature rise of the water is small, and the temperature of the surroundings is carefully controll
Janecke coordinates: Use of a rectangular or Ponchon-type diagram to plot the solvent content of liquid-liquid equilibrium phases, used for solvent-extraction design calculations.
Jeans viscosity equation: An equation which states that the viscosity of a gas is proportional to the temperature raised to a constant power, which is different for different gases.
Jeremiassen crystallizer: Device used to grow solid crystals in a supersaturated liquid solution and to separate them from it.
Jo block: NULL
Johansson block: A type of gage block ground to an accuracy of at least 1/100,000 inch (0.25 micrometer). Also known as Jo block.
Joly steam calorimeter: A calorimeter in which the mass of steam that condenses on a specimen and a pan holding it is measured, as well as the mass of steam that condenses on an empty pan.
Jolly balance: A spring balance used to measure specific gravity of mineral specimens by weighing a specimen when in the air and when immersed in a liquid of known density.
Jordan sunshine recorder: A sunshine recorder in which the time scale is supplied by the motion of the sun, it consists of two opaque metal semicylinders mounted with their curved surfaces facing each other, each of the semicylinders has a short narrow slit in its flat side, sunli