
Article originally published on Noria.com.
In an ideal world, multiple components could be produced in a single piece, or coupled and installed in perfect alignment. However, in the real world, separate components must be brought together and connected onsite. Couplings are required to transmit rotational forces (torque) between two lengths of shaft, and despite the most rigorous attempts, alignment is never perfect.
To maximize the life of components such as bearings and shafts, flexibility must be built in to absorb the residual misalignment that remains after all possible adjustments are made. Proper lubrication of couplings is critical to their performance.
(read the entire article, " The Lubrication Requirements of Couplings", on Noria.com...)