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Alignment Needle Roller Bearings

Alignment needle roller bearings have an outer ring with a convex sphered outside surface. Two polymer seating rings with a concave sphered inside surface that is encased in a drawn sheet steel sleeve are fitted over the outer ring, enabling the bearing to align itself. Alignment needle roller bearings are therefore insensitive to static misalignment of the shaft relative to the housing.

SKF supplies alignment needle roller bearings without an inner ring and with an inner ring. Bearings without an inner ring provide the optimum solution for compact arrangements if the shaft can be hardened and ground. In applications where it is not possible or uneconomical to harden and grind the shaft, bearings with an inner ring should be used.

Alignment needle roller bearing without an inner ring

Alignment needle roller bearing

Bearings with an inner ring permit axial displacement of the shaft relative to the housing within certain limits. The values for the permissible axial displacement are listed in the product table. If greater axial displacements are anticipated, extended inner rings that are wider than standard inner rings can be used. For additional information, refer to the section Needle roller bearing inner rings.

The bearings are supplied without grease and not sealed. Depending on the application, they can be grease or oil lubricated.

The ends of the needle rollers are slightly relieved. The resulting modified line contact between the rollers and raceways means that the load distribution in the bearing is improved.

DimensionsThe dimensions (without an inner ring / with an inner ring) of alignment needle roller bearings have not been standardized. However, with the exception of bearings with a 52 mm outside diameter, the inner ring bore and outside diameter are standardized, in accordance with ISO 15:1998, as follows:

  • bearings with an outside diameter D = 47 mm follow Diameter Series 0
  • bearings with an outside diameter D = 55 mm follow Diameter Series 9

TolerancesInner rings, as well as outer rings with a sphered outside surface are manufactured to Normal tolerances in accordance with ISO 492:2002.

The tolerance for the width of the external drawn steel sleeve is 0,5 mm.

Internal clearanceSKF alignment needle roller bearings with an inner ring have Normal radial internal clearance as standard. The clearance values are listed in the table and are in accordance with ISO 5753-1:2009. They are valid for unmounted bearings under zero measuring load.

SKF alignment needle roller bearings without an inner ring have an inside diameter Fw that lies within F6 tolerance class when the bearing is unmounted and the rollers are in contact with the outer ring raceway. If the recommended tolerance classes (table) are applied, the operational clearance will reach a value in the range of C2 to Normal radial internal clearance (table).

MisalignmentAlignment needle roller bearings can compensate static misalignment up to 3 between the shaft and housing.

These bearings are unable to accommodate any dynamic misalignment.

Permissible operating temperatureDue to the polymer seating ring material, the permissible operating temperature range for alignment needle roller bearings is 30 and +100 C.

CagesSKF alignment needle roller bearings are fitted with a machined steel or a sheet steel cage, with adequate free space for lubricant.

Machined steel cage

Sheet steel cage

Shaft and housing tolerancesAlignment needle roller bearings are mounted with an interference fit in the housing bore. Therefore, shoulders or snap rings are not required to locate the bearing axially so the design of the housing bore is simple and can be produced economically.

If the recommended housing bore tolerance classes listed in the table are applied, alignment movements between the outer ring and the sleeve will be possible. These tolerances, together with the tolerance classes recommended for the inner ring shaft seats or for raceways on the shaft, will reach an operational clearance value in the range of C2 to Normal radial internal clearance (table).

Raceways on the shaftIf the load carrying capacity of an alignment needle roller bearing without an inner ring in applications where the shaft is used as raceway is to be fully exploited, it should have the same hardness and accuracy as a bearing raceway.

The running accuracy of the bearing arrangement also depends on the accuracy of the raceways. For additional information about accuracy, suitable materials, surface roughness and hardness, refer to the section Raceways on shafts and in housings.

Mounting instructionsWhen mounting alignment needle roller bearings, the inner ring should be mounted separately. The outer ring and the polymer seating rings with sleeve and needle roller and cage assembly should be mounted with a mounting dolly. An O-ring provides a simple means of retaining the bearing on the mounting dolly. The stamped side face should abut the flange of the mounting dolly.

Mounting dolly

Note When using grease, the bearing should be lubricated before mounting. Special care should be taken to prevent the sleeve from skewing or tilting when it is being pressed into the housing. Otherwise the rollers and raceways could easily be damaged.

Minimum loadTo achieve satisfactory operation, alignment needle roller bearings must always be subjected to a requisite minimum load. Applying a requisite minimum load is especially important for bearings that operate at high speeds or are subjected to high accelerations or rapid changes in the direction of load. Under these conditions, not applying the correct minimum load can result in damaging sliding movement between the rollers and raceways caused by the inertial forces of the needle roller and friction in the lubricant.

The requisite minimum radial load to be applied to alignment needle roller bearings can be estimated using

Frm = 0,02 C

where

Frm = minimum radial load [kN]

C = basic dynamic load rating [kN]

When starting up at low temperatures or when the lubricant is highly viscous, an even greater minimum load may be required. However, the weight of the components supported by the bearing, together with the external forces, generally exceeds the requisite minimum load. If this is not the case, the alignment needle roller bearing must be subjected to an additional radial load.

Equivalent dynamic bearing load

Alignment needle roller bearings can only accommodate radial loads. Therefore, the equivalent dynamic bearing load is equal to the calculated radial bearing load:

P = Fr

where

P = equivalent dynamic bearing load [kN]

Fr = actual radial bearing load [kN]

Equivalent static bearing load

Alignment needle roller bearings can only accommodate radial loads. Therefore, the equivalent static bearing load is equal to the calculated radial bearing load:

P0 = Fr

where

P0 = equivalent static bearing load [kN]

Fr = actual radial bearing load [kN]


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

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This page is still under construction. All bearing information remains the property and copyright of SKF Group.