The main maintenance issue is the brushes and the shorting rings. The original motors on the Delta Unisaw were repulsion/Induction motors, which of course would get the blade spinning really fast. The motor on my 1952 vintage Unisaw got to the point where the brushes and shorting ring had arced so much that the motor would not run. The repair cost was more than a new motor so I got ahold of a 2 HP 3 phase motor, adapted the mount and put a TECO VFD on it as a phase converter, then used the existing motor starter to start the VFD.