Designs and variants
The ring shoulders can have a different height on one or both bearing rings. Every bearing has the largest possible number of balls, which are guided by a window-type cage.
Bearing seriesThe SKF assortment of super-precision angular contact ball bearings includes bearings in the following dimension series:
- ultra light 718 series
- extremely light 719 series
- light 70 series
- robust 72 series
The cross sections of the four bearing series are compared in fig. 2 for the same bore and same outside diameters. Each bearing series has characteristic features that make it particularly suitable for certain bearing applications.
Where a low cross-sectional height is a critical design parameter, bearings in the 718 series should be selected. If more radial space is available, and loads are not very heavy, bearings in the 719 or 70 series could be used. Bearings in the 72 series have the largest cross-sectional height for a given bore diameter and are suitable for heavy loads at relatively low speeds.
If a high degree of stiffness is required, bearings in the 718 and 719 series are typically used. Bearings in these two series contain the largest number of balls, relative to the selected bore size, and can also accommodate the largest shaft diameter, relative to their outside diameter. Both characteristics are particularly important for system rigidity, as the rigidity of a spindle increases with its shaft diameter, and the rigidity of a bearing arrangement increases with the number of balls.
Contact anglesSuper-precision angular contact ball bearings are manufactured with the following contact angles (fig. 3):
- a 15° contact angle, designation suffix C
- a 25° contact angle, designation suffix AC
For S70 W series bearings, the contact angle is 18° (designation suffix F). For other series, bearings with an 18° contact angle (designation suffix F), are available on request.
A larger contact angle provides a higher degree of axial stiffness and a higher axial load carrying capacity. However, speed capability, radial stiffness, and radial load carrying capacity are reduced.