Nominal Ball Diameter. The diameter value that is used for the purpose of general identification of a ball size; e.g. 1/4", 6mm etc.

Single Diameter of a Ball. The distance between two parallel planes tangent to the surface of the ball.

Mean Diameter of a Ball. The arithmetic mean of the largest and the smallest actual single diameters of the ball.

Ball Diameter Variation. The difference between the largest and the smallest actual single diameters of the ball.

Deviation from Spherical Form. The greatest radial distance in any radial plane between a sphere circumscribed around the ball surface and any point on the ball surface

Lot. A definite quantity of balls manufactured under conditions which are presumed uniform and which is considered and identified as an entity.

Lot Mean Diameter. The arithmetic mean of the mean diameter of the largest ball and that of the smallest ball in the lot

Lot Diameter Variation. The difference between the mean diameter of the largest ball and that of the smallest ball in the lot.

Nominal Ball Diameter Tolerance. The maximum allowable deviation of any ball lot mean diameter from the Nominal Ball Diameter

Specific Diameter. The amount by which the lot mean diameter differs from the nominal diameter, accurate to the marking increment for that grade

Ball Grade. A specific combination of dimensional form and surface roughness tolerances. A ball grade is designated a grade number.

Ball Gauge. The prescribed small amount by which the lot mean diameter should differ from nominal diameter, this amount being one of an established series of amounts

Ball Gauge Deviation. The difference between the lot mean diameter and the sum of the nominal diameter and the ball gauge

Surface Roughness. Surface roughness consists of all those irregularities which form surface relief and which are conventionally defined within the area where deviations of form and waviness are eliminated

Waviness. The more widely spaced circumferential component of surface texture.

Hardness. The measure of resistance to penetration of the ball surface or truncated flat of the ball by a specific indenting shape as determined by specified methods.

Case Depth. The distance measured radially from the surface of the ball to a point where the hardness becomes the equivalent of Rc 50. This term is applicable to case hardened balls only.

Passivation. A chemical treatment to remove corrodible surface impurities and to provide a protective film. This term is applicable to corrosion resisting balls only.