Needle Roller Bearing Inner Rings

SKF supplies inner rings for needle roller bearings separately. They are primarily used in conjunction with needle roller and cage assemblies and drawn cup needle roller bearings in applications where the shaft cannot be ground and hardened to a suitable raceway tolerance. Extended inner rings are also available. These permit greater axial displacement of the shaft, relative to the housing, compared to standard width inner rings. They also provide an excellent counterface for the lips of contact seals.

SKF supplies needle roller bearing inner rings in the following two series:

• inner rings in the IR series, with or without a lubrication hole, with or without machining allowance

Inner Ring
• inner rings in the LR series

Inner Ring – LR Series

Regardless of whether the ring has an interference or loose fit, it should be located to the shaft by either a shoulder or a snap ring to prevent axial movements.

Inner rings in the IR series Inner rings in the IR series are the standard SKF inner rings for needle roller bearings. They are made of carbon chromium bearing steel that has been hardened and ground. The raceway surface, which is precision machined, has a lead-in chamfer on both sides to simplify assembly. The chamfer also protects the sealing lips from damage during the mounting process.

Some sizes of IR inner rings have a lubrication hole. These inner rings are identified by the designation suffix IS1. Inner rings with additional lubrication holes are available on request.

Inner ring with a lubrication hole

Tolerances The bore diameter and the width of IR inner rings are made to Normal tolerances in accordance with ISO 492:2002.

Internal clearance If the recommended shaft and housing tolerance classses are applied, the tolerances for the inner ring raceway diameter F provide applications with the following radial internal clearance:

• a suitable (medium) operational clearance that reaches a value in the range of C2 to C3 radial internal clearance, when combined with SKF drawn cup needle roller bearings. The clearance value depends on the raceway diameter and the operating temperature.
• a Normal radial internal clearance, when combined with SKF needle roller bearings with a machined outer ring. The clearance value are listed in the table and are in accordance with ISO 5753-1:2009. They are valid for unmounted bearings under zero measuring load.

Raceways with a machining allowance On request, SKF can supply inner rings in the IR series with a pre-ground raceway and a machining allowance z. These inner rings are identified by the designation suffix VGS. The machining allowance depends on the inner ring raceway diameter and is listed in the table.

Inner rings in the LR series Inner rings in the LR series are made of carbon chromium bearing steel and have been hardened. The bore and raceway diameter are ground. The side faces are turned and the edges are smoothed. Therefore, they have larger tolerances than inner rings in the IR series. For applications where the larger run-out and width tolerances are less important, these inner rings can be used to provide a cost-effective bearing arrangement. They are, therefore, often combined with drawn cup needle roller bearings or needle roller and cage assemblies.

Inner Ring – LR Series

Inner ring, series LR, combined with a needle roller and cage assembly

Tolerances SKF inner rings in the LR series are manufactured to the following tolerance classes:

• raceway diameter to h6 tolerance class
• width to h12 tolerance class
• bore diameter to K6 tolerance class

The values for the deviation from the nominal dimension for these tolerances are provided in the table.

Inner ring seats The seat for an inner ring mounted on a shaft should be in accordance with the following recommendations.

Shaft diameter tolerances When inner rings are used under conditions of point load and mounted with a loose fit, the seat should be machined to h6 or g6 tolerance class.

When the load rotates, the inner rings should have an interference fit. Sufficient interference can be obtained if the recommended shaft tolerance classes (table) are applied.

Cylindricity The cylindricity of an inner ring seat should be in accordance with ISO 1101:2004, corresponding to the following IT tolerance grades:

• IT5/2 for inner rings under point load
• IT4/2 for inner rings under rotating load

Runout Inner ring shaft abutments should have a run-out corresponding to IT4 tolerance grade.

Supplementary designations The designation suffixes used to identify certain features of SKF needle roller bearing inner rings are explained in the following:

of holes

Needle roller bearings | Needle roller and cage assemblies | Drawn cup needle roller bearings | Needle roller bearings with machined rings | Alignment needle roller bearings | Needle roller bearing inner rings | Universal joint bearings