Inner rings are made from hardened rolling bearing steel and have precision machined or ground raceways. They are used where:
The shaft cannot be used as a raceway for needle roller and cage assemblies, drawn cup needle roller bearings with open ends or with closed ends and needle roller bearings
Needle roller bearings must be combined with wider inner rings in order to allow larger axial displacements of the shaft in relation to the housing
Optimum running surfaces are required for seal lips
Inner rings, precision machined
IR inner rings have a precision machined raceway. Chamfers on the end faces allow easy insertion into the bearing and prevent damage to the seal lips of the bearing. Inner rings are available with and without a lubrication hole.
Inner rings, ground
LR inner rings have a ground raceway. The end faces are turned and the edges are broken. These rings have larger tolerances than the IR rings. They are thus suitable for applications that allow larger width tolerances and less demanding requirements for axial runout.