Ron and Jerry are right, there shouldn't be any reason to remove the drum from the hub. If the drum needs turning, the machine shop will actually prefer having the hub in place to center on the lathe. If the drum is beyond repair (which is highly unlikely) you'll probably end up having to get a used hub/drum assy. anyway, because chances are a salvage yard wouldn't take them apart either.

Keith
If it were easy they'd have grade schoolers doing it!