Spherical plain bearings

Spherical plain bearings are plain bearings, not roller bearings. With plain bearings, the sliding contact takes place between a convex inner race and the convex-shaped bore of the outer race. 

The spherical plain bearing assumes a bearing and guide function through the spherical design of the sliding surfaces. At the same time, misalignment or shaft bending can be compensated and edge pressing avoided. 

Thanks to their straightforward structure, spherical plain bearings have the following advantages over self-aligning ball bearings and spherical roller bearings: 

  • Their large contact surface makes spherical plain bearings relatively insensitive to impact and vibration
  • They provide good noise and impact damping
  • They are more compact i.e. require less design space at significantly lower manufacturing costs   

On the other hand, spherical plain bearings have the following disadvantages: 

  • Relatively high starting friction or starting torque
  • Lower limit speed
  • Oscillating movement sequences often lead to continual start-up phases
  • Poor heat dissipation with compound materials   

In practice, they are often mixed up with pivoting bearings. 

Spherical plain bearings always require maintenance, are generally designed as steel/steel pairs and must be lubricated. 

Increasingly, maintenance-free pairs of plain bearings are being used for dry running. In this case, the sliding surfaces are made of self-lubricating dry plain bearing materials with low friction coefficients (PTFE, MoS2, graphite, PE, silicone). With these, there is no complete separation of the sliding partners on account of the mixed friction.