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Designs and variants

SKF double row full complement cylindrical roller bearings are non-separable and have an annular groove and three lubrication holes in the outer ring to facilitate lubrication. NNF design bearings have three additional lubrication holes in the inner ring.
NNCL design bearings
  • have three integral flanges on the inner ring and no flanges on the outer ring (fig. 1)
  • have a retaining ring in the outer ring between the roller rows to hold the bearing together
    The retaining ring should not be loaded axially during operation.
  • can accommodate axial displacement of the shaft relative to the housing in both directions
NNCF design bearings
  • have three integral flanges on the inner ring and one on the outer ring (fig. 2)
  • have a retaining ring in the outer ring, on the side opposite the integral flange, to hold the bearing together
    The retaining ring should not be loaded axially during operation.
  • are used to locate the shaft axially in one direction and eventually to accommodate axial displacement of the shaft relative to the housing in the opposite direction
NNC design bearings
  • have the same inner ring as NNCL and NNCF design bearings
  • have a two-piece outer ring (fig. 3):
    • held together by retaining elements, which should never be loaded axially
    • consisting of two identical outer ring parts with one integral flange on each
  • are used to locate the shaft axially in both directions
Alternative NNC design bearings may consist of an one-piece outer ring with one integral flange and a flange ring.
NNF design sealed bearings
  • comprise the 50 and 3194.. series
  • have a two-piece inner ring (fig. 4):
    • held together by a retaining ring
    • with three integral flanges
  • have one integral central flange on the outer ring
  • are used to locate the shaft axially in both directions
  • can accommodate tilting moments because of the distance between the two rows of rollers
  • have an outer ring that is 1 mm narrower than the inner ring
  • do not require spacer rings between the inner ring and adjacent components, in applications with a rotating outer ring
  • have two snap ring grooves in the outer ring:
    • to simplify mounting
    • to save space axially
    This is especially valuable where the bearing is mounted in/on an adjacent component, e.g. in rope sheaves (fig. 5).
  • have a PUR contact seal on both sides, fitted in a recess on the inner ring shoulder (fig. 4)
    The seal lips exerts slight pressure against the outer ring raceway.
  • are filled with a high-quality grease with good rust inhibiting properties table 1
    For additional information about greases, refer to Lubrication.
  • can be supplied open and without grease, for applications where oil lubrication is to be used
    If a small quantity of bearings without seals is required, the seals can be removed and the bearings can be washed prior to mounting.

Relubrication

For many application conditions, NNF design sealed bearings do not require relubrication and can be considered relubrication-free (→ Relubrication). However, if they operate in a moist or contaminated environment, or if speeds are moderate to high, relubrication may be necessary. The bearings can be relubricated via lubrication holes in both the inner and outer rings.

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)
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