The duplex bearings have to be specifically mounted in certain arrangements for them to work perfectly. One of the important method for mounting of duplex bearings is face to face arrangement.
The following points can be noted from the arrangement shown in the above figure.
1. The preload offset is provided in the outer race as compared to the inner race offset in the back to back arrangement.
2. The preload is attained by tightening the lock nut provided in the outer race seating bore of the bearing.
3. The load lines tend to converge toward the bore of the bearing. Since the convergence of the load lines is towards the bore of the bearings the arrangement is called as face to face arrangement. This arrangement is also called as the ‘X’ arrangement as the load lines converge to form the shape of ‘X’.
4. This arrangement has the capability to carry heavy thrust loads in both the directions.
This type of arrangement is basically used in areas where misalignment in the shaft needs to be accommodated. Some of the typical uses of this type of arrangement are in high capacity hand grinders and low precision machine tool spindles.
This type of arrangement has some drawback as follows
· The Speed capability of this bearing is very much low as compared to back to back arrangement. This is due to their ability to carry misalignment to certain extent.
· The arrangement requires a higher start up torque compared to back to back arrangement for starting.
· The machining of the threads in the bearing outer race seating bore need to be done perfectly with least error in the perpendicularity.
· The bearings require higher amount of lubrication and special arrangements for cooling as thermal expansion can result in seizure of the bearings.
· Special care is required for this type of mounting while taper roller bearings are used. Care must be taken to ensure that the outer races can be removed easily during dismantling of the bearing and proper provisions provided.
The other method of arrangement – tandem arrangement of duplex bearings will be dealt with in the forthcoming article.