nhbb :: hitech engineering :: preload & duplex bearings

preload & duplex ball bearings

Preload refers to the initial thrust load placed on a set of bearings during installation. Preload allows precise control over the operating geometry of the mating parts to the bearing, and is useful in applications where axial and radial movement must be held within critical limits.

In general, a “built-in preload“ technique is used. When the set of bearings is assembled, the thrust load needed to make the adjacent faces of the rings contact becomes the desired preload. “Built-in preload” helps satisfy the requirements of increased axial and radial stiffness and deflection control.

The three methods of mounting preloaded duplex bearings are back-to-back, face-to-face, and tandem.

When a back-to-back (DB) duplex pair is mounted, the inner rings are drawn together, providing increased stiffness.
When face-to-face (DF) duplex pairs are mounted, the inner rings abut and outer rings are drawn together, providing a higher radial and axial stiffness and accommodation of misalignment.
With tandem (DT) pairs, both inner and outer rings abut and are capable of sharing a thrust load, providing increased thrust capacity.