06/02/2026
— Eliminating Axial Stress on Thrust Bearings —
When performing precision alignment on rotating machinery, technicians often focus entirely on aligning the horizontal and vertical centerlines of the two shafts, while overlooking the critical importance of the coupler gap. The distance between the faces of the two coupling hubs must match the exact engineering specifications of the coupling manufacturer. If the gap is too narrow, thermal expansion during operation will force the shafts against one another, exerting a massive axial load that can quickly destroy thrust bearings. Conversely, if the gap is too wide, it creates excessive axial play and introduces damaging harmonic vibrations.
The essential technical tip is to always verify your coupler gap and check for face angularity across four points before finalizing your alignment. Using a taper gauge, calipers, or specialized laser alignment tools, measure the gap at 90-degree intervals around the circumference of the coupling hub. If the readings vary from top to bottom or side to side, it indicates that the shafts are sitting at an angle to each other, even if their centerlines appear to line up. Correcting this angularity by shimming the machine feet ensures the coupling faces are perfectly parallel and set at the precise operating distance. Taking the time to dial in the correct gap protects your thrust bearings from destructive axial pressures and ensures optimal power transmission.