I've drilled tens of thousands of holes with drill chucks, and rebuilt 20 or
so chucks at work. Other than a few lucky ones, I don't think it's in their
nature to be all that accurate. Albrecht keyless chucks have a fairly
precise guide system for the jaws and seem to run pretty true most of the
time. If I have an occasion to reduce the runout on a drill, I usually use a
collet if the drill diameter matches it, or I select a pilot drill that
does. Collets already match the diameters of center/combined
drill/countersinks.

RJ

"Tidrix" wrote in message
...
I recently bought a Super Chuck model 14N for a floor drill press. This
chuck has a capacity of 0" to 1/2 ". I have been checking the TIR using
jobber length drill bits in the 1/8" to 1/4" diameter range. I noticed
the TIR seems to depend on how hard I tighten a drill bit in the chuck.
For example, if I tighten it just using my hands without the key, the
TIR is under 0.001, but if I fully tighten it using the chuck key the
TIR climbs up to 0.004 or so. If use a #1 drill+countersink bit instead
of a jobber drill bit, the TIR change is even more dramatic with a
shift from under 0.001" to about 0.008". These measurements are all at
the top end of the bit, just under the chuck jaws. Is this normal
behavior for these chucks, or perhaps I got a lemon?