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Non-Standard Housings and Self-Alignment
Not all linear motion applications are the same.

Not all linear motion applications are the same.

Non-standard housing

That is why the Simplicity® family of self-lubricating linear bearings is offered in a range of options designed to handle different housings and shaft alignment requirements.

Most standard applications with average shaft misalignment work well with the standard, straight O.D. “FL” bearings inside the standard “P” pillow block that has a spherical I.D. creating ½ degree misalignment capability in all directions.

But in some conditions, a different setup is required or a customer made housing is needed. In these cases, there are four basic options for non-standard housing fits.

  1. Straight bore housing with press fit bearing for rigid no misalignment capability (Not recommended for the vast majority of Simplicity bearing applications).
  2. Straight bore housing with slip fit bearing for virtually no misalignment capability.
  3. Straight bore housing with slip fit bearing for average misalignment capability.
  4. Straight bore housing with slip fit bearing for severe misalignment conditions.

Simplicity bearing’s self-alignment feature

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.

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.

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.

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