Lee Valley sells an adjustable mandrel which, rather than a collet,
clamps
the rod with a set screw in the MT. This has possibilities so long as
the
hole for the rod is drilled slightly off-axis to allow for the set screw
pushing it to one side. If not, whatever tolerance there is in the hole
diameter will equate directly to runout.


I have the Lee Valley adjustable mandrel. It works fine although I
have never measured the runout. I have never noticed any out of round
whatsoever. It is made in the UK and is 5-6 dollars less expensive
than the fareast versions sold by everyone else.

Charlie Romano