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The ABEC scale is an industry accepted standard for the tolerances of a ball bearing. It was developed by the Annular Bearing Engineering Committee (ABEC) of the American Bearing Manufacturers Association (ABMA). There are five classes from largest to smallest tolerances: 1, 3, 5, 7, and 9. The higher ABEC classes provide better precision, efficiency, and greater speed capabilities, but do not necessarily make the components spin faster. The ABEC rating does not specify many other critical factors, such as smoothness of the rolling contact surfaces, ball precision or quality/type of steel used.
The bearing material is not specified in the ABEC grades. Bearings not conforming to at least ABEC 1 can not be classified as precision bearings as their tolerances are too loose.
The scale is designed to allow a user to make an informed decision about the type of bearing they are purchasing. High rated bearings are intended for precision applications like aircraft instruments or surgical equipment. Lower grades are intended for the vast majority of applications such as vehicles, mechanical hobbies, skates, skateboards, fishing reels and industrial machinery. High ABEC rated bearings allow optimal performance of critical applications requiring very high RPM and smooth operation.
ISO's equivalent standard is ISO 492.
ABEC ISO 492
ABEC 1 normal
ABEC 3 class 6
ABEC 5 class 5
ABEC 7 class 4
ABEC 9 class 2
Actual Changes In Run-out Between Different ABEC Grades
There are a number of factors covered by the ABEC grades. One is the eccentricity (roundness) of the track in the inner ring. The figures given below is the maximum eccentricity allowable.
ABEC 1: 0.0075mm (0.000295'')
ABEC 3: 0.0050mm (0.000197'')
ABEC 5: 0.0035mm (0.000138'')
ABEC 7: 0.0025mm (0.000098'')
ABEC 9: 0.0012mm (0.000047'')
so there is a better data set, yes concentrenticity does matter and no a higher bearing abec rating doesnt mean less clearance the higher does mean some greater clearance