I spent ~42 years in the heavy side of the Industrial Electrical field. Every machine I worked with where shaft to shaft coupling was done, flexible couplings where used.
Even with very heavy machinery, roller chain coupler's were used (Multiple hundreds of Horsepower applications) And Machinists aligned these.
Couplers allow for ease of disassembly, but they also take up things like flexing due to torque loads, temperature variations and stress that could shorten the drive's life.
Often, it is just better to let things run the way they were engineered, and have been proven over countless hours of use.
When you solid couple something, the stresses must be compensated for elsewhere. Like breaking things. Or rubber mounted feet.
But, if you would like to reinvent the wheel, .
