1. A significant change in the rotor imbalance caused by temperature changes.
2. Errors in balance correction equipment, instruments, and calibration mandrel assemblies.
3. Errors caused when the coupling is reassembled and installed on the connected two shafts after balance correction.
4. The imbalance caused by the manufacturing tolerances specified in the design specifications of the coupling body parts (half couplings, etc.).
5. The imbalance caused by the eccentricity of the centering surface of the coupling and the shaft (the coaxiality of the cylinder of the shaft hole and its outer edge).
6. Unbalance caused by uneven material or uneven wear of the parts of the coupling.
7. Unevenness caused by uneven distribution or asymmetry in the attachment (threaded connection, key, shaft end pressure plate) in the coupling.