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.”
The purpose of a radial bearing is to reduce rotational friction and support loads. This is achieved by using two races to hold the balls and to spread the load through the balls. As the bearing race rotates it causes the balls to rotate. The ball provides for substantially less rolling resistance and coefficient of friction than if two flat surfaces were rotating.
Deep Groove Ball Bearings
Single-row, deep groove ball bearings are the most common bearing type, having a wide range of applications. Ball bearings are made with very high levels of precision and used in applications where rotational performance and low torque is necessary, but load is a secondary issue. Deep groove bearings however do have higher load ratings for their size than shallow-groove ball bearings, but are also less tolerant of misalignment.
Ceramic Hybrid Ball Bearings
Ceramic hybrid ball bearings use ceramic balls. Ceramic balls weigh up to 40% less than steel balls, depending on size. This reduces centrifugal loading and skidding, so hybrid ceramic bearings can operate up to 50% faster than conventional bearings. This means that the outer race groove exerts less force inward against the ball as the bearing spins. This reduction in force reduces the friction and rolling resistance. The lighter ball allows the bearing to spin faster, and uses less energy to maintain its speed. Ceramic hybrid ball bearings use these ceramic balls in place of steel balls. They are constructed with steel inner and outer rings, but ceramic balls so they are known as hybrids.
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.”
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