By Joyce Laird, contributing editor
Pillow block bearing inserts have an extended inner ring with different locking devices to enable quick and easy mounting onto the shaft. Design engineers typically request bearing units with the locking mechanism they are most comfortable with. The most common locking mechanism is grub screws:

However, using grub screws imposes an eccentricity between the shaft and the inner ring of the insert bearing. Using an eccentric locking collar also imposes an eccentricity but to a lesser extent. Any eccentricity in the system can lead to unwanted vibration during operation that may not be acceptable for certain applications:

Using SKF ConCentra locking (fig. 1) or an adapter sleeve locking (fig. 2) bearing unit creates a 360° concentric gripon the shaft reducing vibration and eliminating eccentricity allowing for possible increases in shaft rotational speed. The adapter sleeve units are typically not dimensionally interchangeable with the other locking mechanisms, therefore SKF ConCentra units are preferred:

SKF
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