Ball Bearings are a type of rolling-element bearing that uses balls to maintain the separation between the moving parts of the bearing. The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. Radial Ball bearings can support moderate radial loads and moderate axial loads (parallel to the shaft). They can operate at high speeds (400,000 RPMs and higher). Ball bearings with shields or seals for protection can be lubricated to last for the operating life. Sometimes ball bearings are also called “deep groove ball bearings.”
Precision Ball Bearings versus High-Precision Ball Bearings
Generally speaking, precision ball bearings comply to ABEC-1 and ABEC-3 tolerances while high-precision ball bearings comply to ABEC-5, ABEC-7, or ABEC-9 tolerances. Some general purpose ball bearings intentionally do not comply to the ABEC precision tolerance specifications and are not graded nor rated as such.
Super Precision, Super High Precision, and Ultra Precision 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, 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 bearing tolerances and their definition by the ABMA and ANSI, please see our white paper entitled, “Bearing Tolerances and Precision Levels.”
Categories of Ball Bearings Based and Load Handling Capabilities
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