Designs and variants

SKF standard assortment

SKF self-aligning ball bearing variants are:
  • open (fig. 1)
    • with cylindrical bore
    • with tapered bore, e.g. for use with adapter sleeves (fig. 2)
    • with extended inner ring (fig. 3)
  • sealed (fig. 4)
    • with cylindrical bore
    • with tapered bore e.g. for use with adapter sleeves
Sealed bearings

Sealed bearings equipped with contact seals on both sides (fig. 5) are available:

  • in the 22 and 23 series 
  • with bore diameter from 10 to 70 mm
  • with seals made of sheet steel reinforced NBR (oil and wear-resistant, designation suffix 2RS1)

Permissible angular misalignment of sealed bearings is slightly reduced compared to open design bearings. 

Greases for capped bearings

Bearings sealed on both sides are lubricated for the life of the bearing and are virtually maintenance-free. They are filled with one of the following standard greases, which have good corrosion inhibiting properties (table 1):

  • D ≤ 62 → MT47 grease
  • D > 62 → MT33 grease

Grease life for capped bearings

  • is presented as L10, i.e. the time period at the end of which 90% of the bearings are still reliably lubricated
  • depends on the operating temperature and the speed factor (diagram 1)
The grease life specified in diagram 1 is valid for the following combination of operating conditions:
  • horizontal shaft
  • inner ring rotation
  • light load (P ≤ 0,05 C)
  • operating temperature within the green temperature zone of the grease (table 1)
  • stationary machine
  • low vibration levels

Where the operating conditions differ, the grease life obtained from the diagram should be adjusted:

  • vertical shafts → 50% of the obtained value
  • heavier loads (P > 0,05 C) →  apply reduction factor (table 2)
When sealed bearings must operate under certain extreme conditions, such as very high speeds or high temperatures, grease may appear on the capping diameter. For bearing arrangements where this would be detrimental, appropriate actions could be taken. For additional information, contact the SKF application engineering service.
Large self-aligning ball bearings
  • are available in the 130 and 139 series
  • are equipped with an annular groove in the outer ring and (fig. 6):
    • three equally-spaced lubrication holes in the outer ring
    • six equally-spaced lubrication holes in the inner ring
  • can be used in any application where low friction is preferred over high load carrying capacity (e.g. in paper industry)
Bearings with an extended inner ring
  • are (fig. 7) designed for less demanding applications that use commercial grade shafting
  • have a special bore tolerance, class JS7 (table 3), that facilitates mounting and dismounting
  • are located axially on the shaft by means of a slot at one end of the inner ring that engages a pin or shoulder screw (fig. 8) fitted to the shaft. This also prevents the shaft from spinning in the bearing bore.
Cages

Depending on their series and size, SKF self-aligning ball bearings are fitted with one of the cages shown in table 4.

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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