Precision Classes

The most common bearing precision classes are determined by ISO (International Organization for Standardization), DIN (translated to German Institute for Standardization) and of course ABEC (Annular Bearing Engineering Committee of the American Bearing Manufacturers Association (ABMA). These standards provide precision dimensional specifications to which the bearing manufacture must conform. This allows the end user to design mating parts with the understanding of how they will interact with the mechanical system.

When designing a complex mechanical system, the stack up of tolerance is a critical importance. The tolerance band is then necessary to determine the fits of the bearing within the shaft and housing. These standards can also provide clarity as to how the bearings will impact the system with dimensions such as runout, roundness, taper and parallelism. For example, increased parallelism can have positive impacts on running torque while a reduced bearing runout can better balance system. 


The engineers at Carter Manufacturing can help you understand when a higher precision class is necessary for your design and provide empirical data of the impact. In some cases the additional cost implication will not be justified and it’s important to validate these decisions.

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