I don't have a Super model, but I've noticed on a couple of my larger chucks
that when small diameters are chucked, the jaws can distort outward. The
grip pressure is near the tips of the jaws, instead of back inside the chuck
body.
You could try chucking a drill blank (or a straight locating punch) fully
seated in the chuck, for another check.
I think that when the small drills (particularly short ones) are only
partially inserted into a big chuck, the jaws don't hold true.

When I need to use small drills without changing to a smaller chuck, I use
arbors to hold them (the arbor is seated more deeply in the chuck). A
setscrew in the arbor holds the drills securely, although the drill needs to
have a small flat spot ground in it.

WB
..............


"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?