"Grant Erwin" wrote: You may get away with single-hole tightening on a
quality chuck in new condition, but I *always* tighten all 3. (clip)
^^^^^^^^^^^^^^^^
I think Grant has put his finger on it. When you tighten a chuck in one
hole, you rotate the geared sleeve, but you also push all the clearance to
one side. If the chuck is new and in good condition, this will be minimal,
but there will always be some. So, as the chuck tightens, the same friction
that holds it closed will hold the jaws slightly off center. Applying the
chuck key to each of the holes in succession keeps pushing the jaws closer
to perfect concentricity.