Ball Bearings

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 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, precision ball 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 subsequently are less expensive compared to fully compliant ABEC-9 (Ultra Precision) bearings. For more about official precision bearing tolerances and their definition by the ABMA and ANSI, please see our white paper entitled, "Bearing Tolerances and Precision Levels."

Ball bearings are typically divided into three overall general categories depending on the direction of the loads they are designed to encounter (radial, axial, or combination of each load respectively) including:

• Radial Ball Bearings - primarily radial loads
• Thrust Ball Bearings - primarily axial loads
• Angular Contact Ball Bearings - a combination of radial and axial loads

Not All Ball Bearings Are "Radial" Ball Bearings

Most ball bearing units are radial ball bearings; however, there are other types of bearings that use balls as their rolling element which are not classified as "radial" ball bearings. These include:

• Linear Bushing Ball Bearings
• Linear Way Bearings