NN Inc., Corporate Office
2000 Waters Edge Dr, Ste 12
Johnson City, TN  37604
Phone: 423-743-9151   
FAX: 423-743-2670

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  Grades & Tolerances

Per ANSI/ABMA/ISO 3290:1998 specification,

"Rolling Bearings – Balls – Dimensions and Tolerances"

Issued February 16, 2000

Terminology:

• 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) – the 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.

ANSI/ABMA/ISO 3290 Standard Grades and Tolerances:

NOTE – The values given in this table do not take into account surface defects; hence measurement must be taken outside such defects.