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

**Ball Gage Deviation: **The difference between the lot mean diameter and the sum of the nominal diameter and the ball gage.

**Ball Diameter Variation:** The difference between the largest and the smallest actual single diameter of the ball.

**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.

**Deviation from Spherical Form:** The greatest radial distance in a radial plane between a sphere circumscribed around the surface of the ball and other points on the surface of the ball.

**Grade:** A specific combination of dimensional form and surface roughness tolerance. A ball grade is designated by a grade number. Ex G100, 200 etc

**Hardness:** The measure of resistance to penetration of the ball surface or truncated flat of the ball by a specific indenting shape.

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

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

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

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

**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.

**Nominal Ball Diameter Tolerance:** The maximum allowable deviation of any ball by a specific indenting shape.

**Specific Diameter:** The amount by which the lot mean diameter differs from the nominal diameter, accurate to the container marking increment for that grade. The specific diameter should be marked on the unit container.

**Sphericity (roundness):** The radial distance of the maximum peak from the perfect circle plus the distance of the maximum valley from the perfect circle.

**Surface Roughness:** Surface roughness consist 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.