Does a self-aligning bearing eliminate the need to align the housing?

The short answer

No. Self-alignment accommodates a specified angular relationship inside the bearing, within its manufacturer-defined conditions. It does not automatically align seals, couplings or adjacent bearings. A small-wind generator can therefore need accurate housing alignment even when a self-aligning bearing is part of its documented design.

Locate the alignment freedom

The bearing geometry may let the inner assembly orient relative to the outer ring. That is different from moving the housing centre or correcting parallel offset between two shaft supports. A self-aligning bearing cannot simply reposition every connected component. The permitted angular movement also depends on the particular bearing, load and surrounding geometry, so its name cannot establish an unlimited assembly allowance.

Check what remains constrained

A seal lip, close-clearance cover or rigidly connected coupling may tolerate less angular movement than the bearing itself. Two supports can also constrain the shaft together in a way not visible from either bearing alone. The alignment review should therefore distinguish internal accommodation from the overall shaft line and neighboring clearances. A bearing-only capability is not automatically the limiting allowance of the assembled machine.

Ask for the system alignment limit

Request the actual bearing designation, permitted internal misalignment and the tighter constraints imposed by seals, covers, coupling and support layout. NSK describes self-aligning bearing geometry, but that general feature does not establish a MARSTON component choice. The decision is whether the complete interface allows the predicted movement. Do not use the word self-aligning to waive drawing requirements, shim a machine arbitrarily or accept a housing offset without the equipment designer’s assessment of all connected parts. A neighboring bearing or seal can be the controlling angular constraint. The equipment drawing should therefore state the assembly allowance instead of expecting the installer to select the largest individual component misalignment value.