SKF Angular contact thrust ball bearings for screw drives
Machine tools require screw drives that can position a work piece or machine component quickly, efficiently, and precisely. To meet these requirements, screw drives can be supported at both ends by SKF super-precision angular contact thrust ball bearings. The bearings provide a high degree of axial stiffness, high axial load carrying capacity, accommodate high speeds and rapid accelerations, and offer very high running accuracy.
Angular contact thrust ball bearings for screw drives are well suited for screw drive applications, but are also beneficial in other applications, where reliable radial and axial support is required, together with extremely precise axial guidance of the shaft.
Product details
The SKF assortment of super-precision angular contact thrust ball bearings for screw drives can accommodate virtually any requirement placed on support bearings for screw drives. The main criteria used when selecting bearings to support screw drives are axial stiffness and load carrying capacity, running accuracy, speed, and frictional moment. Other factors to consider can be the moment stiffness of a bearing arrangement or the ability to cope with misalignment between the shaft and housing. Mounting and seal requirements also need to be considered
Single direction bearings
Are available in the BSA and BSD series
Are available for shaft diameters from 12 to 75 mm
Are non-separable
Have a 62° contact angle
The transition radius between the raceway and shoulder on both rings is ground. This reduces edge stresses by approximately 30%, enabling these bearings to accommodate heavy axial loads and incidental overloading better than conventional designs.
Single direction bearings are designed to accommodate axial loads in one direction only and are therefore adjusted against a second bearing or mounted as sets. The bearings are universally matchable, as standard, and can be mounted in sets of up to four bearings for a variety of bearing arrangements, reaching the performance level of matched sets.
Universally matchable bearings are specifically manufactured so that when mounted in random order, but immediately adjacent to each other, preload within a predetermined range and effective load sharing will result without the use of shims or similar devices. They have very tight tolerances for the bore and outside diameter as well as for radial run-out.
A unique heat treatment helps to maintain a constant bearing preload over the entire service life of the bearings.
Matched bearing sets
Single direction bearings can be supplied as matched sets on request. However, because the standard bearings are universally matchable, SKF recommends reducing inventory by ordering single bearings only and arranging them in sets as required.
Bearing arrangements
Back-to-back arrangement
In a back-to-back arrangement the load lines diverge along the bearing axis. Axial loads acting in both directions can be accommodated, but only by one bearing or bearing set in each direction.
Bearings mounted back-to-back provide a relatively rigid bearing arrangement. The wide span between bearing effective centres makes this arrangement particularly well suited to support moment loads.
Face-to-face arrangement
In a face-to-face arrangement the load lines converge along the bearing axis. Axial loads acting in both directions can be accommodated, but only by one bearing or bearing set in each direction.
The shorter span between effective bearing centres makes face-to-face arrangements less suitable to support moment loads compared to bearings in a back-to-back arrangement.
Tandem arrangement
The use of a tandem arrangement provides increased axial and radial load carrying capacity compared to a single bearing. In a tandem arrangement, the load lines are parallel so that radial and axial loads are shared.
The bearing set can only accommodate axial loads acting in one direction. If axial loads act in both directions, or if combined loads are present, additional bearing(s) adjusted against the tandem arrangement must be added.
Examples
Universally matchable single direction bearings can be arranged in various ways depending on the stiffness and load requirements of the application. The possible arrangements are shown in, including the applicable designation suffixes for matched sets.
If misalignment cannot be avoided between the bearing positions, face-to-face bearing arrangements are recommended. They are less sensitive to misalignment than back-to-back bearing arrangements.
Combinations of tandem arrangements with back-to-back or face-to-face arrangements are usually selected to maximize the stiffness or load carrying capacity of a bearing set in a particular direction. This is the case, for example, when extended, preloaded, vertical or overhung screw drives must be supported.