On May 6, 5:17*pm, Wes wrote:
...
You drilled the hole with the lathe. *Drilling a hole by turning the work vs turning the
drill tends to make the straightest hole. It also tends to drive the drill to the center
of rotation of the work piece. * Why wouldn't running a reamer have the same benefit from
the unique properties of drilling on a lathe?
Wes

On my old lathe the drill bit obviously tries to center itself but
can't always overcome the handicaps of age and infirmity (the
machine's). Before reaming I run a boring bar in and usually can hear
some eccentricity and taper in the cut.

I've found combinations of chuck and tailstock position that drill
straighter than others. The best is a Collis center drill holder with
the tailstock almost fully retracted.
http://www.collistoolholder.com/cgi-...yp=CAT_9_TYP_Q

If your tailstock has a keying slot maybe you could pop the chuck off
the adapter and see if you can find a new position for it that
counteracts other arbor and tailstock spindle errors like droop or not
being exactly at headstock spindle height.

jsw