Variable TIR on Super Chuck
 

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?

Variable TIR on Super Chuck
 

Does a "Super Chuck" have a key? I tighten my keyed chucks progressivly in
all three holes twic around. This seems to help me.


"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?

Variable TIR on Super Chuck
 

I went through some of this too on the same chuck. Some of my problem was
how I seated the chuck on the arbor adaptor. I reseated on the jt33 (?) a
couple of times until runout was .002 but it never went away. As Tom said
have you tried adjusting tightening in steps. Can you trace the high spot
of the runout to one position on the chuck or is it moving around?
lg
no neat sig line
"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?

Variable TIR on Super Chuck
 

In article om, Tom
Gardner wrote:

Does a "Super Chuck" have a key? I tighten my keyed chucks progressivly in
all three holes twic around. This seems to help me.


It is a Jacobs ball bearing Super Chuck and it has a key. When
tightening with the key I have tried using a single hole as well as all
three holes with similar results.

Variable TIR on Super Chuck
 

Now that I think about it, I have one of those chucks too, in a lathe. I
don't know where I got it but it was used and always had run-out. I Just
thought it was worn, maybe accuracy is not it's inherent strength. I only
use it when I really, really don't want a bit to spin in it 'cuz I can
tighten the shi* out of it.

"Tidrix" wrote in message
...
In article om, Tom
Gardner wrote:

Does a "Super Chuck" have a key? I tighten my keyed chucks progressivly
in
all three holes twic around. This seems to help me.


It is a Jacobs ball bearing Super Chuck and it has a key. When
tightening with the key I have tried using a single hole as well as all
three holes with similar results.

Variable TIR on Super Chuck
 

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?

Variable TIR on Super Chuck
 

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?

Variable TIR on Super Chuck
 

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?

The point of the ball-bearing chucks is higher gripping capacity on account
of reduced friction in the tightening works. The jaws fit looser than in
precision keyless chucks so there's bound to be more slop. Also the high
gripping capacity makes it easy to spring and permanently damage the jaws by
over-tightening the jaws on a bit that doesn't reach all the way to the back
of the jaws. If your chuck is not new it has probably suffered that abuse.

I'm sure happy with them though and would not use anything else for heavy
drilling.

It should not be a problem with a #1 center drill but the larger
double-ended ones are a problem, as the smooth part of the body doesn't
reach the back of the jaws.

Bob