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Designs and variants

Common designs

The most common design of single row cylindrical roller bearings are shown here.

NU design bearings (fig. 1)

  • have two integral flanges on the outer ring and no flanges on the inner ring
  • can accommodate axial displacement of the shaft relative to the housing in both directions
  • can be used together with an appropriate angle ring to stabilize the bearing in the axial direction (→ Appropriate angle rings)

N design bearings (fig. 2)

  • have two integral flanges on the inner ring and no flanges on the outer ring
  • can accommodate axial displacement of the shaft relative to the housing in both directions

NJ design bearings (fig. 3)

  • have two integral flanges on the outer ring and one on the inner ring
  • can accommodate axial displacement of the shaft relative to the housing in one direction only
  • are used to locate the shaft axially in one direction
  • can be used together with an appropriate angle ring to stabilize the bearing in the other axial direction (→ Appropriate angle rings)

NUP design bearings (fig. 4)

  • 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
  • are used to locate the shaft axially in both directions

Inch bearings

The design of SKF inch bearings in the CRL and CRM series (→ product table) conforms to the metric N design (fig. 2). They are mainly used in the aftermarket and, therefore, SKF recommends not to use these bearings for new bearing arrangement designs.

Appropriate angle rings (thrust collars)

  • are used with NU design bearings to 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 clamping of the rollers.
  • are used with NJ design bearings to locate the shaft axially in both directions (fig. 6)
  • are made of carbon chromium steel
  • are hardened and ground
  • have a maximum axial run-out that is in accordance with the Normal tolerance class for the appropriate bearing
  • are identified by the series designation HJ followed by the appropriate bearing dimension series and size
  • are available as listed in the product table
  • must be ordered separately

Reasons to design angle rings into a bearing arrangement include:

  • no NJ or NUP design locating bearings in the product range
  • to provide an extend inner ring seat for heavily loaded bearings in the locating position:
    • full width inner ring seat of NJ design bearings with an HJ angle ring compared to NUP design bearings having a shorter inner ring and a loose flange
  • to simplify design or mounting procedures
Other designs

NUB design bearings (fig. 7)

  • have two integral flanges on the outer ring and no flanges on the inner ring that is extended on both sides
  • can accommodate axial displacement of the shaft relative to the housing in both directions

NJP design bearings (fig. 8)

  • have two integral flanges on the outer ring and one non-integral flange, i.e. a loose flange ring, on the inner ring
  • are used to locate the shaft axially in one direction

NF design bearings (fig. 9)

  • have two integral flanges on the inner ring and one integral flange on the outer ring
  • are used to locate the shaft axially in one direction

NP design bearings (fig. 10)

  • have two integral flanges on the inner ring and one integral flange and one non-integral flange, i.e. a loose flange ring, on the outer ring
  • are used to locate the shaft axially in both directions
Other variants

Bearings without an inner or outer ring

  • are available based on:
    • NU design bearings without an inner ring (RNU series, fig. 11)
      → enable the shaft diameter to be larger to provide a stronger, stiffer shaft
      → provide inside diameter Fw tolerance limits to be within F6Ⓔ when the rollers are in contact with the outer ring raceway
      → are listed in the product table for certain sizes
    • N design bearings without an outer ring (RN series, fig. 12)
  • can accommodate axial displacement, of the shaft relative to the housing, limited by the width of the raceway:
    • on the shaft for RNU bearings
    • in the housing for RN bearings
  • are typically used in applications where hardened and ground raceways can be machined on the shaft or in the housing (→ Raceways on shafts and in housings)

Bearings with a tapered bore (fig. 13)

  • are available with a 1:12 tapered bore (designation suffix K)
  • have radial internal clearance greater than corresponding bearings with a cylindrical bore

Bearings with a snap ring groove in the outer ring (fig. 14)

  • are identified by the designation suffix N
  • can be axially located in the housing by a snap ring:
    • to save space
    • to reduce mounting time

Bearings with locating slots in the outer ring (fig. 15)

  • are available with one or two locating slots (designation suffix N1 or N2)
    The two locating slots are positioned 180° apart.
  • can be used to prevent the outer ring from turning where it must be mounted with a loose fit
Matched bearings
  • are combined so that any difference in cross-section height of the bearings used in a matched set lies within a very small tolerance range
    This tighter tolerance is a precondition for equal load sharing between the bearings.
  • can be supplied as:
    • sets of two bearings (designation suffix DR)
    • sets of three bearings (designation suffix TR)
    • sets of four bearings (designation suffix QR)
Cages

SKF single row cylindrical roller bearings are fitted with one of the cages shown in table 1.

When used at high temperatures, some lubricants can have a detrimental effect on polyamide cages. For additional information about the suitability of cages, refer to Cages and Cage materials.

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