Needle Roller Bearing Inner Rings are utilised in applications where the shaft cannot be ground and hardened to a suitable raceway tolerance. Inner Rings are available in 2 main types:
IR series - Manufactured from hardened and ground bearing steel the raceway surface is precision machined and has a lead-in chamfer on both sides to simplify assembly. Some sizes are available with an lubrication hole, this is identified with the suffix "IS1".
LR series - Manufactured from hardened bearing steel, the bore and outside diameter are ground. The side faces are turned and the edges are smoothed. these inner rings have larger tolerances then the IR type.