On Jan 26, 2014, at 3:53 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
   In a similar
manner, I think that if a drive can be slightly modified so
 that the hub clamp has a slight eccentricity (with respect to the
 spindle), a pattern would result upon writing that centered around the  
 Sure, that;s essentaily the pattern on n analogue alignment disk.
 I think machining the drive hub to give the rigth degree of sccentricity
 would be non-trivial. 
 
Not with a milling machine and a boring head.  Or perhaps even a lathe with a 4-jaw chuck
and careful checking with a dial indicator.
        paul