A flexible coupling makes assembly more forgiving, but it does not remove the need to align the shafts. The published radial and angular values are useful acceptance boundaries. Staying well inside them gives the elastomer more of its capacity for damping and small operating movement instead of permanent installation error.
Before fitting the hubs
Confirm the model, finished bore and keyway against each shaft. Inspect the shaft for burrs or damage and verify the hub can be installed without forcing it into position. If the design calls for a fit tolerance or retention method, follow the confirmed drawing or order document rather than improvising at assembly.
Set the axial relationship deliberately.
The NM table publishes an S dimension with tolerance for every model. Use the model-specific value during assembly and check that the hubs do not bottom against each other or leave an unintended large separation. The coupling guard should also leave enough room for inspection.
Align in both radial and angular directions.
Measure rather than judge by eye. Bring the shafts into alignment, tighten the machine feet and re-check. If connecting pumps or process machinery, verify that piping or connected equipment has not shifted the driven machine. After the first operating period, inspect for unusual elastomer wear, hub movement or fretting.
