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Designs and variants

Basic design bearings

SKF basic design double row cylindrical roller bearings are available in several designs. The major design differences between the bearings are the configuration of the inner and outer ring flanges and the cage design and material. The most popular designs are:

Bearing designFlange configurationsCage design
NNU design
  • outer ring: three integral
  • inner ring: none
  • one cage
  • machined brass or steel
  • double prong-type
  • roller centred
NNU.1 design
  • outer ring: three integral
  • inner ring: none
  • two cages
  • machined brass
  • window-type
  • roller centred
NNU.2 design
  • outer ring: one integral central and two loose
  • inner ring: none
  • one cage
  • machined brass or steel
  • double prong-type
  • roller centred
NNU.3 design
  • outer ring: three integral
  • inner ring: none
  • two cages
  • machined steel
  • pin-type
  • pierced rollers
NNU.4 design
  • outer ring: one integral central and two loose
  • inner ring: none
  • two cages
  • machined steel
  • pin-type
  • pierced rollers
NNU.5 design
  • outer ring: two integral
  • inner ring: none
  • one cage
  • machined brass
  • window-type
  • roller centred
NNU.6 design
  • outer ring: two integral
  • inner ring: none
  • one cage
  • machined steel
  • pin-type
  • pierced rollers
NNU.7 design
  • outer ring: one integral and one loose
  • inner ring: none
  • one cage
  • machined brass
  • window-type
  • roller centred
NNUB design
  • outer ring: three integral
  • extended inner ring: none
  • one cage
  • machined brass or steel
  • double prong-type
  • roller centred
NNUB.1 design
  • outer ring: one integral central and two loose
  • extended inner ring: none
  • one cage
  • machined brass or steel
  • double prong-type
  • roller centred
NNUB.2 design
  • outer ring: two integral
  • extended inner ring: none
  • one cage
  • machined brass
  • window-type
  • roller centred
NNUB.3 design
  • outer ring: two integral
  • extended inner ring: none
  • one cage
  • machined steel
  • pin-type
  • pierced rollers
NNUB.4 design
  • outer ring: three integral
  • extended inner ring: none
  • two cages
  • machined brass
  • window-type
  • roller centred
NNUB.5 design
  • outer ring: one integral central and two loose
  • extended inner ring: none
  • two cages
  • machined steel
  • pin-type
  • pierced rollers
NNUP design
  • outer ring: three integral
  • inner ring: one integral and two loose
  • one cage
  • machined brass or steel
  • double prong-type
  • roller centred
NNUP.1 design
  • outer ring: two integral and one loose
  • inner ring: one integral and one loose
  • two cages
  • machined steel
  • pin-type
  • pierced rollers
NN design
  • outer ring: none
  • inner ring: three integral
  • one cage
  • machined brass or steel
  • double prong-type
  • roller centred
NN.1 design
  • outer ring: none
  • inner ring: three integral
  • two cages
  • either PA66 or stamped steel
  • window-type
  • roller centred
NN.2 design
  • outer ring: none
  • inner ring: three integral
  • two cages
  • machined steel
  • pin-type
  • pierced rollers
NN.3 design
  • outer ring: none
  • inner ring: one integral and two loose
  • two cages
  • machined steel
  • pin-type
  • pierced rollers
Variants/features

Where double row cylindrical roller bearings are to be mounted with a loose fit on the shaft or roll neck (e.g. to allow rapid roll changes) they can be supplied with one or more additional features (fig. 1) to compensate for disadvantages of the loose fit. The helical groove in the bore and/or lubrication grooves in the side faces of the bearing rings enable effective lubrication to be provided for the sliding contact surfaces.

Bearings equipped with one or more of these features are identified in the Design variant/feature (→ product table) as described in the following:

GHelical groove in inner ring bore
KTapered bore
= taper 1:12 for K
= taper 1:30 for K30
WLubrication grooves in the side faces of the bearing rings
WILubrication grooves in the side faces of the inner ring
WOLubrication grooves in the side faces of the outer ring
W20Lubrication holes in outer ring
W33Annular groove and lubrication holes in outer ring
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 double row cylindrical roller bearings are fitted with one or two 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.

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