I was struggling with a glassworking lathe recently.. All went well, until I tried to start the motor 😉 My original shaft (inside the small bearings) connected to motor’s shaft was made from aluminium. But probably during pressing it into bearings and pulley, it bent slightly, so it became eccentric 🙁 So the shaft was made from scratch from steel and pressed to pulley again.. Unfortunately, the hole in the shaft was drilled 0.2mm bigger, so after locking the motor’s shaft into the hole in steel shaft it was eccentric again 😉 So I removed the screws on the motor holder and let it to prop against another screw.. It looks crazy, but works very well, the holder is moving up and down, but it works.. I placed a small strip of rubber between the holder and screw, now the vibrations aren’t transfered into whole construction and it is less loud..