Self-aligning capability with regards to linear plain bearings refers to the ability to handle slight misalignments or shaft deflection. Achieving perfect parallelism in a parallel shaft configuration is very difficult. In addition, keeping all mounting holes in perfect alignment with the shaft adds to the challenge. Simplicity bearings and pillow blocks that offer self-aligning capability can alleviate some of those challenges.
Simplicity linear plain bearings are able to achieve this self-aligning capability in one of two ways. The FL/FM/FJ series of bearings are available with a straight cylindrical outside diameter (OD) as standard. Also offered as an option are the FLA/FMA/FJA series, and these all feature a crowned, or spherical, OD.
- Use the standard straight OD bearings (FL/FM/FJ) with all standard Simplicity housings, pillow blocks, and flange mount housings. These housings have the self-aligning capability designed into the inside diameter (ID), or bore. This built-in feature provides up to ½ degree of self-alignment in all directions, allowing for some shaft deflection and misalignment.
2. Use the FLA/FMA/FJA series with the OD crown. This crowned feature would be used where the mating housing bore is straight, such as a custom housing on the machinery, or a straight-bore pillow block. This bearing configuration then offers the same ability for the bearing to rock/pivot within the bore and handle up to ½ degree of misalignment in all directions.
It is also important to mention a third configuration related to self-aligning capabilities, and that is the use of a straight OD bearing in straight bore housing. This DOES NOT allow for any self-alignment and provides a very rigid assembly. These are typically used in single shaft applications, and offer a solution where tighter repeatability and precision are required.
NOTE: Sometimes there is confusion between self-aligning feature and compensated fit of the bearing. Please keep in mind that self-aligning refers to the OD of the bearing and ID of PBC’s standard housings. The term “compensated” refers to the fit of the ID of the bearing to the shaft. A bearing or pillow block can have both features (self-alignment and compensated ID), or neither one. This concept will be discussed in a separate topic.