**Nominal ball diameter (Dw)**
>>** T he diameter value that is used for the purpose of general identification of a ball size.**
Single diameter of a ball (Dws)
>> It is 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 diameter of the ball.
Deviation from spherical form (tDw)
>> The greatest radial distance in any radial plane between a sphere circumscribed around the ball surface or any point on the ball surface.
Lot
**>>** A definite quantity of balls manufactured under conditions which are assumed to be uniform and considered ** **and identified as an entity.
**Lot Diameter Variation (VDWL)**
**>>** The difference between the mean diameter of the largest ball and 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.
**Ball Grade**
**>>** A ball is allotted a grade number which id s combination of dimensional, form and surface roughness tolerances.
**Preferred gauge (S)**
**>>** The prescribed small amount by which the lot mean diameter should differ from nominal diameter. 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**
**>>** Difference between the lot mean diameter and the sum of the nominal ball diameter and the ball gauge.
**Ball sub-gauge**
**>>** It is the selected amount of an established series of amounts and 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 but must not be used by purchaser to order.
**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 Hardness (Ra)**
**>>** Consist of those irregularities which form surface relief and are conventionally defined within the area where deviations of form and waviness are eliminated. |