Designs and variants

SKF standard assortment

  • bearings in the 72 B(E) and 73 B(E) series with 40° contact angle (fig. 1)
  • some sizes in the 70 B series
  • sealed bearings:
    • in series 72 B(E) (15 ≤ d ≤ 55 mm)
    • in series 73 B(E) (12 ≤ d ≤ 50 mm)
  • bearings in the 72 AC series with 25° contact angle (15 ≤ d ≤ 70 mm)
  • bearings in the 73 AC series with 25° contact angle (17 ≤ d ≤ 70 mm)
  • some large size bearings with a flanged outer ring
  • SKF inch bearings (ALS and AMS series)
Basic design bearings
  • are intended for adjusted arrangements where only one bearing is used at each bearing position and are not suitable for mounting immediately adjacent to each other
  • have Normal tolerances on bearing width and standout of the rings
  • have different performance capabilities compared with SKF Explorer bearings
Bearings for universal matching
  • are available with 25° and 40° contact angles
  • are intended to be used in sets
  • have ring widths and standouts manufactured to tight tolerances
  • can also be used in place of basic design bearings for arrangements with single bearings, as they typically have higher precision, and increased load carrying capacity and speed capability

When two bearings are mounted immediately adjacent to each other, a given internal clearance or preload or an even load distribution between the two bearings is obtained without the use of shims or similar devices.

Bearings for universal matching are identified by the following suffixes:

  • CA, CB, CC or G for internal clearance
  • GA, GB or GC for preload

When ordering, indicate the number of individual bearings required and not the number of sets.

Paired mounting can be done in three ways:

Tandem arrangement (fig. 2)
  • is used where the load carrying capacity of a single bearing is inadequate
  • shares the radial and axial loads equally
  • has parallel load lines
  • can accommodate axial loads in one direction only
    If axial loads act in both directions, a third bearing, adjusted against the tandem pair, must be added.
Back-to-back arrangement (fig. 3)
  • provides a relatively stiff bearing arrangement
  • can accommodate tilting moments
  • has load lines that diverge from the bearing axis
  • can accommodate axial loads in both directions, but only by one bearing in each direction
Face-to-face arrangement (fig. 4)
  • is less sensitive to misalignment but not as stiff as a back-to-back arrangement
  • has load lines that converge towards the bearing axis
  • can accommodate axial loads in both directions, but only by one bearing in each direction
Bearings with 25° contact angle (AC series)
  • have a raceway geometry optimized for high speeds
  • have reduced sensitivity to axial loading and misalignment, including the ability to accommodate two times higher peak loads before edge stresses can occur
  • are equipped with an optimized machined brass cage as standard
Compared with bearings with 40° contact angle, benefits include:
  • 20% higher limiting speeds
  • higher radial load carrying capacity (by trading off lower axial load carrying capacity)
  • increased robustness when used as the backup bearing in sets that are predominantly loaded in one direction
Sealed bearings

SKF supplies single row angular contact ball bearings in the 72 B(E) and 73 B(E) series, which are sealed on both sides. For additional information, refer to Integral sealing.

Non-contact seals (designation suffix 2RZ, fig. 5)

  • have no additional frictional moment
  • have the same limiting speeds as open bearings
  • form an extremely narrow gap with the inner ring shoulder
  • are made of sheet steel reinforced NBR (oil and wear-resistant)
  • make good, positive contact with the recess in which they are fitted
When capped bearings must operate under certain conditions, such as very high speeds or high temperatures, grease may appear between the inner ring and capping device. For bearing arrangements where this would be detrimental, appropriate actions should be taken.

Greases for sealed bearings

Bearings sealed on both sides are lubricated for the life of the bearing and are virtually maintenance-free. They are filled as standard with high performance polyurea grease (GXN, no designation suffix) → table 1.

Non-standard greases are available on request.

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 (diagram 1)
  • depends on:
    • the operating temperature
    • the ndm value
    • grease performance factor (GPF) (table 1)
The indicated grease life is valid under this 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 as described below, the grease life obtained from the diagrams should be adjusted:

  • vertical shafts → 50% of the obtained value
  • heavier loads (P > 0,05 C) → apply reduction factor (table 2)

SKF single row angular contact ball bearings are fitted with one of the cages shown in table 3. The machined brass cage (designation suffix M) has been upgraded as follows:

  • optimized cage pocket geometry
  • a smaller cross section and reduced mass
  • increased material strength with reduced lead content

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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