“Precision” and “high-precision” are generic bearing terms; however, there is no official definition for either in the bearing industry. Generally speaking, “precision” ball bearings comply with ABEC-1 and ABEC-3 tolerances while “high-precision” ball bearings comply with ABEC-5, ABEC-7, or ABEC-9 tolerances.
Some general purpose ball bearings intentionally do not comply with the ABEC precision tolerance specifications and are not graded or rated as such.
Some factories promote bearings as “Super Precision (MM),” “Super High Precision (MMV),” and “Ultra Precision (MMX)” bearings. These are all just factory defined terms to used describe ABEC-7 through ABEC-9 (ISO-P4 through ISO-P2) tolerances with one of them being a compromise between the two specifications.
More specifically, bearings called Super Precision(MM) are typically manufactured to ABEC-7 (ISO-P4) tolerances. Ultra Precision (MMX) bearings are usually manufactured to ABEC-9 (ISO P-2) tolerances. However, so-called Super High Precision (MMV) bearings are manufactured partly to ABEC-7 tolerances, but also partly to tolerances defined by ABEC-9 specifications. Super High Precision bearings operate with performance levels and running accuracy meeting ABEC-9 specifications; however, their remaining features meet ABEC-7 specifications and consequently are less expensive compared to fully ABEC-9 compliant (Ultra Precision) bearings.
For more about official bearing tolerances and their definition by the ABMA and ANSI, please see our white paper entitled, Bearing Tolerances and Precision Levels.
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