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## Nominal Ball Diameter – DW

The diameter value that is used for the purpose of general identification of a ball size.

## Single Diameter of a Ball – DWS

The distance between two parallel planes tangent to the surface of the ball.

## Mean Diameter of a Ball – DWM

The arithmetical mean of the largest and the smallest single diameters of the ball.

## Ball Diameter Variation – VDWS

The difference between the largest and the smallest single diameters of the ball.

## Deviation from Spherical Form – TDW

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:

## Lot Mean Diameter – DWML

The arithmetical mean of the diameter of the largest ball and that of the smallest ball in the lot.

## Lot Diameter Variation – VDWL

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

## Gauge Interval – IG

One of the intervals into which the deviation of the nominal diameter of ball is divided.

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

## Preferred Gauge - S

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. Each ball gauge is a whole multiple of the ball precision grade. The ball gauge, combined with the precision grade and the nominal ball diameter, can be considered the most correct dimensional identification to pass orders.

## Deviation from Ball Gauge – ΔS

Difference between the lot mean diameter and the sum of the nominal ball diameter and the ball gauge.

## Ball Sub-Gauge

The selected amount of an established series of amounts. It is the closest one to the real deviation from ball gauge. Each ball sub-gauge is whole multiple of the interval sub-gauge fixed for the ball grade. The ball sub-gauge is used by supplier to specify the lot mean diameter.

## Hardness

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

## Surface Roughness - Ra

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