# Definitions

#### 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.

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. 