Eccentricity: in cylinders, the condition resulting from the inside and outside diameters not having a common center; a condition that occurs when a shaft rotating in a sleeve bearing does not have a common center with the bearing.

Elastohydrodynamic (EHL or EHD) lubrication: a thin-film form of lubrication in which an elastic deformation occurs between two non-conforming components in loaded contact: at the same time, the high load in this small contact area causes a temporary, extreme increase in viscosity that traps the lubricant momentarily in the contact area, greatly increasing its load- carrying capacity.

Elastomer: a rubber or rubber-like natural or synthetic material that can be stretched repeatedly and that returns to its approximate original dimensions when the stress is released.

Electrorheological fluids: fluids currently under development whose rheological properties change in the presence of an electric field. Typically, these fluids increase in viscosity in the presence of the field, then revert back to their previous viscosity when the field is shut off.

Electrostatic oiler: machine that uses electrostatically charged oil particles to deposit coating oils on steel sheets.

Emulsifier: a substance that promotes the formation of a stable emulsion. In industrial maintenance cleaning, emulsifiers are used to modify the surface tension of liquid droplets (dispersed phase) to keep them from coalsecing (agglomerating); the resulting emulsion suspends soil in solution.

Emulsibility: the capacity of a fluid insoluble in water to form an emulsion with water.

Emulsion: colloidal dispersion of one immiscible liquid in another; the second suspends, but does not dissolve, the first. Emulsions of oil and water are formed either by agitation or with the aid of an emulsifying agent. In the water-in-oil type, water droplets are held in suspension as the internal phase; in the oil-inwater type, oil droplets are held in suspension and water is the continuous phase. Both types exhibit a milky or cloudy appearance. The water-in-oil type is known as an invert emulsion, as the oil is the continuous phase.

End-of-line system (lube systems): system in which the two main supply lines are dead-ended at the last measuring valve; usually installed where lubrication points are in a line.

Endurance limit stresses (gears): stresses that can be imposed repeatedly, indefinitely, without causing surface fatigue failure. Following Buckingham, AGMA uses the endurance limit for reversed bending as the working stress in bending for gear teeth; these values approximate 250 times the Bhn.

Enveloping worm (gears): worm with one or more threads, increasing in diameter from its middle portion toward each end, to conform to the curvature of the gear; has more surface contact than a straight worm.

EP (Extreme Pressure) lubricants: lubricants formulated with additives to prevent sliding metal surfaces from direct contact and seizing under extreme loads; under such conditions, the high local temperature at the interface causes the additives to react, combining chemically with the metal surfaces to form a protective film that prevents welding or seizure. The principal EP additives are compounds of sulfur, phosphorus and chlorine; common laboratory tests for EP properties include ASTM D-2509 and D-2782 and ASTM D-2596 and D-2783.

EPA: Environmental Protection Agency
Essential oils (odor masks): natural oily liquids with marked characteristic odors obtained from plants, flowers, leaves, etc., often used for masking odors or imparting odors, especially to metalworking fluids or gear oil. Pine and lemon oils are most commonly used.

Ester: chemical compound produced by the reaction of an acid and an alcohol, resulting in an elimination of a molecule of water.

Evaporative loss: the portion of a lubricant that volatilizes in use or in storage; applies especially to lubricants containing solvents or water, with high vapor pressures (see ASTM D-972 and D-2595).