When you made the last pass did you just disengage the clutch, or place the power feed selector lever on the apron in neutral or perhaps put the reversing lever in neutral? If you just disengaged the clutch then the problem is in the apron and it will required removal and disassembly. If you had to move the power feed selector lever then the problem is still in the apron. If it required placing the reversing lever in neutral to free it up then the problem is in the gear train between the headstock and gearbox at the left end of the lathe or in the gearbox itself. First check and see if there is any binding in the gear train, if not then the gearbox is binding and will require removal and disassebly.
