• Grade
  The ball grade (G) is a specific combination of dimensional, form, surface roughness and sorting tolerance for balls. For example, the level of sphericity, expressed in millionths of an inch, e.g., a Grade 10 ball must be round or spherical within 10 millionths of an inch. The grade designation also dictates the other tolerances, per the chart shown below. 
  
• Variation of Ball Diameter (VDws)
  Tthe difference between the largest and the smallest of the single diameters of a ball.
  
• Variation of Ball Lot Diameter (VDwL)
  The difference between the mean diameters of the largest ball and smallest ball in a ball lot.
  
• Ball Lot
  Definite quantity of balls manufactured under conditions presumed uniform and which is considered as an entity.
• Deviation from Spherical Form
  The difference between the largest and smallest diameters measurable on a single ball. Also referred to as roundness or sphericity.
  
• Surface Roughness (Ra)
  Surface irregularities with relatively small spacings, which usually include irregularities resulting from the method of manufacture being used and/or other influences.

Grades (AFBMA) / Tolerances  Chrome and Stainless Steel Balls