Grades of Precision
BEARINGS are manufactured to standard grades of precision with established tolerances for size and geometric accuracy. These standards are known as ABEC classes as set by the Annular Bearing Engineers Committee of the American Bearing Manufacturer's Association (ABMA). These standards are also accepted by (ANSI) American National Standards Institute and by international agreement for the standards developed by (ISO) International Organization of Standardization.
The ABEC scale is a system of rating the manufacturing tolerance of precision bearings. The system was developed by the Annular Bearing Engineering Council (ABEC), a division of the American Bearing Manufacturers' Association ABMA). The ABMA was formerly known as the Anti-Friction Bearing Manufacturers' Association. Bearings rated under the ABEC systems are typically called "precision bearings", with a rating or class from 1 to 9. ABEC 1 meets a looser tolerance and ABEC 9 meets high precision tight bearing tolerances. ABEC class is not to be confused with radial play, which is discussed further down.
* For ABEC 9 Bearings with Outer Diameters from 0.787 to 0.875
O.D tolerance = +0 / -1.5
Radial Runout = 1
Groove Runout with Reference Side = 1