What is O arrangement X arrangement?

O arrangement (BACK-TO-BACK)

With the ‘back to back’ bearing pair the inner rings are claimed together. The contact angle lines between the outer ring raceway, ball and inner raceway diverge. This results in a maximum spread giving high rigidity. This is the reason why this type of duplex bearing is most commonly used. 

Advantages：

1）Less sensitive to the thermal gradient than face-to-face arrangement

2）Easy mounting on the shaft

3）Self contained assembly on the shaft

Disadvantages ：

1）Higher sensitivity to misalignment than face-to-face

2）Difficult dismounting

X Arrangement (FACE-TO-FACE)

With the ‘face to face’ bearing pair the outer rings are claimed together. The contact lines converge resulting in a smaller spread and more elastically.

Advantages

1）Higher misalignment capabilities than back-to-back

2）Permits disassembly in screw compressors without destroying one of the bearing

Disadvantages

1）No self-contained assembly on the shaft

2）More sensitive to thermal gradient than back-to-back