Basic design bearings

SKF basic design single row cylindrical roller bearings are available in several designs. The main difference is the configuration of the flanges. The most popular designs are:
  • NU design (fig. 1)
    NU design bearings have two integral flanges on the outer ring and no flanges on the inner ring. These bearings can accommodate axial displacement of the shaft relative to the housing in both directions.
  • N design (fig. 2)
    N design bearings have two integral flanges on the inner ring and no flanges on the outer ring. These bearings can accommodate axial displacement of the shaft relative to the housing in both directions.
  • NJ design (fig. 3)
    NJ design bearings have two integral flanges on the outer ring and one on the inner ring. These bearings are used to locate the shaft axially in one direction. They can accommodate axial displacement of the shaft relative to the housing in one direction only.
  • NUP design (fig. 4)
    NUP design bearings have two integral flanges on the outer ring and one integral flange and one non-integral flange i.e. a loose flange ring, on the inner ring. These bearings are used to locate the shaft axially in both directions.
The design of SKF inch bearings in the CRL and CRM series (→ product table) conforms to the metric N design. They are mainly used in the aftermarket and, therefore, SKF recommends not to use these bearings for new bearing arrangement designs.

Angle rings (thrust collars)

To stabilize NU and NJ design bearings in the axial direction, SKF can supply angle rings. When used with an angle ring, NU design bearings locate the shaft axially in one direction (fig. 5). Angle rings should not be used on both sides of NU design bearings as this can lead to axial compression of the rollers. NJ design bearings combined with an angle ring are used to locate the shaft axially in both directions (fig. 6).
There can be several reasons to design angle rings into a bearing arrangement:
  • When NJ or NUP design locating bearings are not in the product range.
  • To provide a more effective inner ring seat for heavily loaded bearings in the locating position. An arrangement of an NJ design bearing with an HJ angle ring have a full width inner ring seat, instead of using an NUP design bearing that has a shorter inner ring and a loose flange.
  • To simplify design or mounting procedures.

SKF angle rings are made of carbon chromium steel. They are hardened and ground. The maximum axial run-out is in accordance with the Normal tolerance class for the appropriate bearing. Available angle rings are listed in the product table. They are identified by the series designation HJ followed by the appropriate bearing dimension series and size. Angle rings must be ordered separately.

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