During the coupling instalation,there may have a situation of misalignment of the two shafts(as the pic below). After installation with situation of misalignment,there will have a periodically deforming of the shaft and the support while the shaft system rotating.Because the two half shafts need to keep into the original state. So it will have a problem of forced vibration and will aggravate the wear of the support shaft. So, the most important is ensure theconnectricity error of the two revolving shafts.  The centered installation requests as below.